postgres.git / summary / log / commit / refs
commit eea081ad013d657a2a7857bd591cfcb559c9a94d
Author: Tom Lane <tgl@sss.pgh.pa.us>
Date: Thu Jun 10 16:27:27 2021 +0000
First released in: 14.0, 11.13, 12.8, 13.4
Rearrange logrep worker's snapshot handling some more.
It turns out that worker.c's code path for TRUNCATE was also
careless about establishing a snapshot while executing user-defined
code, allowing the checks added by commit 84f5c2908 to fail when
a trigger is fired in that context.
We could just wrap Push/PopActiveSnapshot around the truncate call,
but it seems better to establish a policy of holding a snapshot
throughout execution of a replication step. To help with that and
possible future requirements, replace the previous ensure_transaction
calls with pairs of begin/end_replication_step calls.
Per report from Mark Dilger. Back-patch to v11, like the previous
changes.
Discussion: https://postgr.es/m/B4A3AF82-79ED-4F4C-A4E5-CD2622098972@enterprisedb.com
src/backend/replication/logical/worker.c | 70 +++++++++++++++++---------------
1 file changed, 38 insertions(+), 32 deletions(-)
diff --git a/src/backend/replication/logical/worker.c b/src/backend/replication/logical/worker.c
index f8c52b4ccc1..e00cc423494 100644
--- a/src/backend/replication/logical/worker.c
+++ b/src/backend/replication/logical/worker.c
@@ -154,30 +154,41 @@ should_apply_changes_for_rel(LogicalRepRelMapEntry *rel)
}
/*
- * Make sure that we started local transaction.
+ * Begin one step (one INSERT, UPDATE, etc) of a replication transaction.
*
- * Also switches to ApplyMessageContext as necessary.
+ * Start a transaction, if this is the first step (else we keep using the
+ * existing transaction).
+ * Also provide a global snapshot and ensure we run in ApplyMessageContext.
*/
-static bool
-ensure_transaction(void)
+static void
+begin_replication_step(void)
{
- if (IsTransactionState())
- {
- SetCurrentStatementStartTimestamp();
-
- if (CurrentMemoryContext != ApplyMessageContext)
- MemoryContextSwitchTo(ApplyMessageContext);
+ SetCurrentStatementStartTimestamp();
- return false;
+ if (!IsTransactionState())
+ {
+ StartTransactionCommand();
+ maybe_reread_subscription();
}
- SetCurrentStatementStartTimestamp();
- StartTransactionCommand();
-
- maybe_reread_subscription();
+ PushActiveSnapshot(GetTransactionSnapshot());
MemoryContextSwitchTo(ApplyMessageContext);
- return true;
+}
+
+/*
+ * Finish up one step of a replication transaction.
+ * Callers of begin_replication_step() must also call this.
+ *
+ * We don't close out the transaction here, but we should increment
+ * the command counter to make the effects of this step visible.
+ */
+static void
+end_replication_step(void)
+{
+ PopActiveSnapshot();
+
+ CommandCounterIncrement();
}
@@ -194,13 +205,6 @@ create_estate_for_relation(LogicalRepRelMapEntry *rel)
ResultRelInfo *resultRelInfo;
RangeTblEntry *rte;
- /*
- * Input functions may need an active snapshot, as may AFTER triggers
- * invoked during finish_estate. For safety, ensure an active snapshot
- * exists throughout all our usage of the executor.
- */
- PushActiveSnapshot(GetTransactionSnapshot());
-
estate = CreateExecutorState();
rte = makeNode(RangeTblEntry);
@@ -241,7 +245,6 @@ finish_estate(EState *estate)
/* Cleanup. */
ExecResetTupleTable(estate->es_tupleTable, false);
FreeExecutorState(estate);
- PopActiveSnapshot();
}
/*
@@ -631,7 +634,7 @@ apply_handle_insert(StringInfo s)
TupleTableSlot *remoteslot;
MemoryContext oldctx;
- ensure_transaction();
+ begin_replication_step();
relid = logicalrep_read_insert(s, &newtup);
rel = logicalrep_rel_open(relid, RowExclusiveLock);
@@ -642,6 +645,7 @@ apply_handle_insert(StringInfo s)
* transaction so it's safe to unlock it.
*/
logicalrep_rel_close(rel, RowExclusiveLock);
+ end_replication_step();
return;
}
@@ -668,7 +672,7 @@ apply_handle_insert(StringInfo s)
logicalrep_rel_close(rel, NoLock);
- CommandCounterIncrement();
+ end_replication_step();
}
/*
@@ -727,7 +731,7 @@ apply_handle_update(StringInfo s)
bool found;
MemoryContext oldctx;
- ensure_transaction();
+ begin_replication_step();
relid = logicalrep_read_update(s, &has_oldtup, &oldtup,
&newtup);
@@ -739,6 +743,7 @@ apply_handle_update(StringInfo s)
* transaction so it's safe to unlock it.
*/
logicalrep_rel_close(rel, RowExclusiveLock);
+ end_replication_step();
return;
}
@@ -840,7 +845,7 @@ apply_handle_update(StringInfo s)
logicalrep_rel_close(rel, NoLock);
- CommandCounterIncrement();
+ end_replication_step();
}
/*
@@ -862,7 +867,7 @@ apply_handle_delete(StringInfo s)
bool found;
MemoryContext oldctx;
- ensure_transaction();
+ begin_replication_step();
relid = logicalrep_read_delete(s, &oldtup);
rel = logicalrep_rel_open(relid, RowExclusiveLock);
@@ -873,6 +878,7 @@ apply_handle_delete(StringInfo s)
* transaction so it's safe to unlock it.
*/
logicalrep_rel_close(rel, RowExclusiveLock);
+ end_replication_step();
return;
}
@@ -934,7 +940,7 @@ apply_handle_delete(StringInfo s)
logicalrep_rel_close(rel, NoLock);
- CommandCounterIncrement();
+ end_replication_step();
}
/*
@@ -955,7 +961,7 @@ apply_handle_truncate(StringInfo s)
ListCell *lc;
LOCKMODE lockmode = AccessExclusiveLock;
- ensure_transaction();
+ begin_replication_step();
remote_relids = logicalrep_read_truncate(s, &cascade, &restart_seqs);
@@ -996,7 +1002,7 @@ apply_handle_truncate(StringInfo s)
logicalrep_rel_close(rel, NoLock);
}
- CommandCounterIncrement();
+ end_replication_step();
}
[parent: 534b9be805b4]