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[PATCH v2 1/2] Do not lock tables in get_tables_to_repack(). 11+ messages / 4 participants [nested] [flat]
* [PATCH v2 1/2] Do not lock tables in get_tables_to_repack(). @ 2026-06-16 06:49 ChangAo Chen <[email protected]> 0 siblings, 0 replies; 11+ messages in thread From: ChangAo Chen @ 2026-06-16 06:49 UTC (permalink / raw) When doing a whole database repack, we build a list of repackable tables and take a lock on them to prevent concurrent drops. But concurrent drops can always happen after we build the list because we process each table in a separate transaction. The ConditionalLockRelationOid() also makes the default behavior like SKIP_LOCKED, which is unexpected. To remove the locks, we need to make repack_is_permitted_for_relation() handles concurrent drops correctly: it should not report an error when failing to search the syscache in pg_class_aclcheck(). Use pg_class_aclcheck_ext() instead to detect a concurrent drop. Also check the return value of get_rel_name(). While at it, replace relation_close() with table_close() to match the table_open(). --- src/backend/commands/repack.c | 67 ++++++++++------------------------- 1 file changed, 19 insertions(+), 48 deletions(-) diff --git a/src/backend/commands/repack.c b/src/backend/commands/repack.c index faa07d1a118..2879c8af574 100644 --- a/src/backend/commands/repack.c +++ b/src/backend/commands/repack.c @@ -2169,22 +2169,9 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) index = (Form_pg_index) GETSTRUCT(tuple); - /* - * Try to obtain a light lock on the index's table, to ensure it - * doesn't go away while we collect the list. If we cannot, just - * disregard it. Be sure to release this if we ultimately decide - * not to process the table! - */ - if (!ConditionalLockRelationOid(index->indrelid, AccessShareLock)) - continue; - - /* Verify that the table still exists; skip if not */ classtup = SearchSysCache1(RELOID, ObjectIdGetDatum(index->indrelid)); if (!HeapTupleIsValid(classtup)) - { - UnlockRelationOid(index->indrelid, AccessShareLock); continue; - } classForm = (Form_pg_class) GETSTRUCT(classtup); /* Skip temp relations belonging to other sessions */ @@ -2192,7 +2179,6 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) !isTempOrTempToastNamespace(classForm->relnamespace)) { ReleaseSysCache(classtup); - UnlockRelationOid(index->indrelid, AccessShareLock); continue; } @@ -2201,10 +2187,7 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) /* noisily skip rels which the user can't process */ if (!repack_is_permitted_for_relation(cmd, index->indrelid, GetUserId())) - { - UnlockRelationOid(index->indrelid, AccessShareLock); continue; - } /* Use a permanent memory context for the result list */ oldcxt = MemoryContextSwitchTo(permcxt); @@ -2228,45 +2211,20 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) class = (Form_pg_class) GETSTRUCT(tuple); - /* - * Try to obtain a light lock on the table, to ensure it doesn't - * go away while we collect the list. If we cannot, just - * disregard the table. Be sure to release this if we ultimately - * decide not to process the table! - */ - if (!ConditionalLockRelationOid(class->oid, AccessShareLock)) - continue; - - /* Verify that the table still exists */ - if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(class->oid))) - { - UnlockRelationOid(class->oid, AccessShareLock); - continue; - } - /* Can only process plain tables and matviews */ if (class->relkind != RELKIND_RELATION && class->relkind != RELKIND_MATVIEW) - { - UnlockRelationOid(class->oid, AccessShareLock); continue; - } /* Skip temp relations belonging to other sessions */ if (class->relpersistence == RELPERSISTENCE_TEMP && !isTempOrTempToastNamespace(class->relnamespace)) - { - UnlockRelationOid(class->oid, AccessShareLock); continue; - } /* noisily skip rels which the user can't process */ if (!repack_is_permitted_for_relation(cmd, class->oid, GetUserId())) - { - UnlockRelationOid(class->oid, AccessShareLock); continue; - } /* Use a permanent memory context for the result list */ oldcxt = MemoryContextSwitchTo(permcxt); @@ -2279,7 +2237,7 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) } table_endscan(scan); - relation_close(catalog, AccessShareLock); + table_close(catalog, AccessShareLock); return rtcs; } @@ -2357,15 +2315,28 @@ get_tables_to_repack_partitioned(RepackCommand cmd, Oid relid, static bool repack_is_permitted_for_relation(RepackCommand cmd, Oid relid, Oid userid) { + bool is_missing = false; + Assert(cmd == REPACK_COMMAND_CLUSTER || cmd == REPACK_COMMAND_REPACK); - if (pg_class_aclcheck(relid, userid, ACL_MAINTAIN) == ACLCHECK_OK) + if (pg_class_aclcheck_ext(relid, userid, ACL_MAINTAIN, &is_missing) == ACLCHECK_OK) return true; - ereport(WARNING, - errmsg("permission denied to execute %s on \"%s\", skipping it", - RepackCommandAsString(cmd), - get_rel_name(relid))); + /* Report a warning if the relation still exists. */ + if (!is_missing) + { + char *relname; + + relname = get_rel_name(relid); + if (relname != NULL) + { + ereport(WARNING, + errmsg("permission denied to execute %s on \"%s\", skipping it", + RepackCommandAsString(cmd), relname)); + + pfree(relname); + } + } return false; } -- 2.47.3 --op6mnexl7cn72cto Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename=v2-0002-fixups.patch ^ permalink raw reply [nested|flat] 11+ messages in thread
* [PATCH v2 1/2] Do not lock tables in get_tables_to_repack(). @ 2026-06-16 06:49 ChangAo Chen <[email protected]> 0 siblings, 0 replies; 11+ messages in thread From: ChangAo Chen @ 2026-06-16 06:49 UTC (permalink / raw) When doing a whole database repack, we build a list of repackable tables and take a lock on them to prevent concurrent drops. But concurrent drops can always happen after we build the list because we process each table in a separate transaction. The ConditionalLockRelationOid() also makes the default behavior like SKIP_LOCKED, which is unexpected. To remove the locks, we need to make repack_is_permitted_for_relation() handles concurrent drops correctly: it should not report an error when failing to search the syscache in pg_class_aclcheck(). Use pg_class_aclcheck_ext() instead to detect a concurrent drop. Also check the return value of get_rel_name(). While at it, replace relation_close() with table_close() to match the table_open(). --- src/backend/commands/repack.c | 67 ++++++++++------------------------- 1 file changed, 19 insertions(+), 48 deletions(-) diff --git a/src/backend/commands/repack.c b/src/backend/commands/repack.c index faa07d1a118..2879c8af574 100644 --- a/src/backend/commands/repack.c +++ b/src/backend/commands/repack.c @@ -2169,22 +2169,9 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) index = (Form_pg_index) GETSTRUCT(tuple); - /* - * Try to obtain a light lock on the index's table, to ensure it - * doesn't go away while we collect the list. If we cannot, just - * disregard it. Be sure to release this if we ultimately decide - * not to process the table! - */ - if (!ConditionalLockRelationOid(index->indrelid, AccessShareLock)) - continue; - - /* Verify that the table still exists; skip if not */ classtup = SearchSysCache1(RELOID, ObjectIdGetDatum(index->indrelid)); if (!HeapTupleIsValid(classtup)) - { - UnlockRelationOid(index->indrelid, AccessShareLock); continue; - } classForm = (Form_pg_class) GETSTRUCT(classtup); /* Skip temp relations belonging to other sessions */ @@ -2192,7 +2179,6 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) !isTempOrTempToastNamespace(classForm->relnamespace)) { ReleaseSysCache(classtup); - UnlockRelationOid(index->indrelid, AccessShareLock); continue; } @@ -2201,10 +2187,7 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) /* noisily skip rels which the user can't process */ if (!repack_is_permitted_for_relation(cmd, index->indrelid, GetUserId())) - { - UnlockRelationOid(index->indrelid, AccessShareLock); continue; - } /* Use a permanent memory context for the result list */ oldcxt = MemoryContextSwitchTo(permcxt); @@ -2228,45 +2211,20 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) class = (Form_pg_class) GETSTRUCT(tuple); - /* - * Try to obtain a light lock on the table, to ensure it doesn't - * go away while we collect the list. If we cannot, just - * disregard the table. Be sure to release this if we ultimately - * decide not to process the table! - */ - if (!ConditionalLockRelationOid(class->oid, AccessShareLock)) - continue; - - /* Verify that the table still exists */ - if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(class->oid))) - { - UnlockRelationOid(class->oid, AccessShareLock); - continue; - } - /* Can only process plain tables and matviews */ if (class->relkind != RELKIND_RELATION && class->relkind != RELKIND_MATVIEW) - { - UnlockRelationOid(class->oid, AccessShareLock); continue; - } /* Skip temp relations belonging to other sessions */ if (class->relpersistence == RELPERSISTENCE_TEMP && !isTempOrTempToastNamespace(class->relnamespace)) - { - UnlockRelationOid(class->oid, AccessShareLock); continue; - } /* noisily skip rels which the user can't process */ if (!repack_is_permitted_for_relation(cmd, class->oid, GetUserId())) - { - UnlockRelationOid(class->oid, AccessShareLock); continue; - } /* Use a permanent memory context for the result list */ oldcxt = MemoryContextSwitchTo(permcxt); @@ -2279,7 +2237,7 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) } table_endscan(scan); - relation_close(catalog, AccessShareLock); + table_close(catalog, AccessShareLock); return rtcs; } @@ -2357,15 +2315,28 @@ get_tables_to_repack_partitioned(RepackCommand cmd, Oid relid, static bool repack_is_permitted_for_relation(RepackCommand cmd, Oid relid, Oid userid) { + bool is_missing = false; + Assert(cmd == REPACK_COMMAND_CLUSTER || cmd == REPACK_COMMAND_REPACK); - if (pg_class_aclcheck(relid, userid, ACL_MAINTAIN) == ACLCHECK_OK) + if (pg_class_aclcheck_ext(relid, userid, ACL_MAINTAIN, &is_missing) == ACLCHECK_OK) return true; - ereport(WARNING, - errmsg("permission denied to execute %s on \"%s\", skipping it", - RepackCommandAsString(cmd), - get_rel_name(relid))); + /* Report a warning if the relation still exists. */ + if (!is_missing) + { + char *relname; + + relname = get_rel_name(relid); + if (relname != NULL) + { + ereport(WARNING, + errmsg("permission denied to execute %s on \"%s\", skipping it", + RepackCommandAsString(cmd), relname)); + + pfree(relname); + } + } return false; } -- 2.47.3 --op6mnexl7cn72cto Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename=v2-0002-fixups.patch ^ permalink raw reply [nested|flat] 11+ messages in thread
* [PATCH v2 1/2] Do not lock tables in get_tables_to_repack(). @ 2026-06-16 06:49 ChangAo Chen <[email protected]> 0 siblings, 0 replies; 11+ messages in thread From: ChangAo Chen @ 2026-06-16 06:49 UTC (permalink / raw) When doing a whole database repack, we build a list of repackable tables and take a lock on them to prevent concurrent drops. But concurrent drops can always happen after we build the list because we process each table in a separate transaction. The ConditionalLockRelationOid() also makes the default behavior like SKIP_LOCKED, which is unexpected. To remove the locks, we need to make repack_is_permitted_for_relation() handles concurrent drops correctly: it should not report an error when failing to search the syscache in pg_class_aclcheck(). Use pg_class_aclcheck_ext() instead to detect a concurrent drop. Also check the return value of get_rel_name(). While at it, replace relation_close() with table_close() to match the table_open(). --- src/backend/commands/repack.c | 67 ++++++++++------------------------- 1 file changed, 19 insertions(+), 48 deletions(-) diff --git a/src/backend/commands/repack.c b/src/backend/commands/repack.c index faa07d1a118..2879c8af574 100644 --- a/src/backend/commands/repack.c +++ b/src/backend/commands/repack.c @@ -2169,22 +2169,9 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) index = (Form_pg_index) GETSTRUCT(tuple); - /* - * Try to obtain a light lock on the index's table, to ensure it - * doesn't go away while we collect the list. If we cannot, just - * disregard it. Be sure to release this if we ultimately decide - * not to process the table! - */ - if (!ConditionalLockRelationOid(index->indrelid, AccessShareLock)) - continue; - - /* Verify that the table still exists; skip if not */ classtup = SearchSysCache1(RELOID, ObjectIdGetDatum(index->indrelid)); if (!HeapTupleIsValid(classtup)) - { - UnlockRelationOid(index->indrelid, AccessShareLock); continue; - } classForm = (Form_pg_class) GETSTRUCT(classtup); /* Skip temp relations belonging to other sessions */ @@ -2192,7 +2179,6 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) !isTempOrTempToastNamespace(classForm->relnamespace)) { ReleaseSysCache(classtup); - UnlockRelationOid(index->indrelid, AccessShareLock); continue; } @@ -2201,10 +2187,7 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) /* noisily skip rels which the user can't process */ if (!repack_is_permitted_for_relation(cmd, index->indrelid, GetUserId())) - { - UnlockRelationOid(index->indrelid, AccessShareLock); continue; - } /* Use a permanent memory context for the result list */ oldcxt = MemoryContextSwitchTo(permcxt); @@ -2228,45 +2211,20 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) class = (Form_pg_class) GETSTRUCT(tuple); - /* - * Try to obtain a light lock on the table, to ensure it doesn't - * go away while we collect the list. If we cannot, just - * disregard the table. Be sure to release this if we ultimately - * decide not to process the table! - */ - if (!ConditionalLockRelationOid(class->oid, AccessShareLock)) - continue; - - /* Verify that the table still exists */ - if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(class->oid))) - { - UnlockRelationOid(class->oid, AccessShareLock); - continue; - } - /* Can only process plain tables and matviews */ if (class->relkind != RELKIND_RELATION && class->relkind != RELKIND_MATVIEW) - { - UnlockRelationOid(class->oid, AccessShareLock); continue; - } /* Skip temp relations belonging to other sessions */ if (class->relpersistence == RELPERSISTENCE_TEMP && !isTempOrTempToastNamespace(class->relnamespace)) - { - UnlockRelationOid(class->oid, AccessShareLock); continue; - } /* noisily skip rels which the user can't process */ if (!repack_is_permitted_for_relation(cmd, class->oid, GetUserId())) - { - UnlockRelationOid(class->oid, AccessShareLock); continue; - } /* Use a permanent memory context for the result list */ oldcxt = MemoryContextSwitchTo(permcxt); @@ -2279,7 +2237,7 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) } table_endscan(scan); - relation_close(catalog, AccessShareLock); + table_close(catalog, AccessShareLock); return rtcs; } @@ -2357,15 +2315,28 @@ get_tables_to_repack_partitioned(RepackCommand cmd, Oid relid, static bool repack_is_permitted_for_relation(RepackCommand cmd, Oid relid, Oid userid) { + bool is_missing = false; + Assert(cmd == REPACK_COMMAND_CLUSTER || cmd == REPACK_COMMAND_REPACK); - if (pg_class_aclcheck(relid, userid, ACL_MAINTAIN) == ACLCHECK_OK) + if (pg_class_aclcheck_ext(relid, userid, ACL_MAINTAIN, &is_missing) == ACLCHECK_OK) return true; - ereport(WARNING, - errmsg("permission denied to execute %s on \"%s\", skipping it", - RepackCommandAsString(cmd), - get_rel_name(relid))); + /* Report a warning if the relation still exists. */ + if (!is_missing) + { + char *relname; + + relname = get_rel_name(relid); + if (relname != NULL) + { + ereport(WARNING, + errmsg("permission denied to execute %s on \"%s\", skipping it", + RepackCommandAsString(cmd), relname)); + + pfree(relname); + } + } return false; } -- 2.47.3 --op6mnexl7cn72cto Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename=v2-0002-fixups.patch ^ permalink raw reply [nested|flat] 11+ messages in thread
* [PATCH v2 1/2] Do not lock tables in get_tables_to_repack(). @ 2026-06-16 06:49 ChangAo Chen <[email protected]> 0 siblings, 0 replies; 11+ messages in thread From: ChangAo Chen @ 2026-06-16 06:49 UTC (permalink / raw) When doing a whole database repack, we build a list of repackable tables and take a lock on them to prevent concurrent drops. But concurrent drops can always happen after we build the list because we process each table in a separate transaction. The ConditionalLockRelationOid() also makes the default behavior like SKIP_LOCKED, which is unexpected. To remove the locks, we need to make repack_is_permitted_for_relation() handles concurrent drops correctly: it should not report an error when failing to search the syscache in pg_class_aclcheck(). Use pg_class_aclcheck_ext() instead to detect a concurrent drop. Also check the return value of get_rel_name(). While at it, replace relation_close() with table_close() to match the table_open(). --- src/backend/commands/repack.c | 67 ++++++++++------------------------- 1 file changed, 19 insertions(+), 48 deletions(-) diff --git a/src/backend/commands/repack.c b/src/backend/commands/repack.c index faa07d1a118..2879c8af574 100644 --- a/src/backend/commands/repack.c +++ b/src/backend/commands/repack.c @@ -2169,22 +2169,9 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) index = (Form_pg_index) GETSTRUCT(tuple); - /* - * Try to obtain a light lock on the index's table, to ensure it - * doesn't go away while we collect the list. If we cannot, just - * disregard it. Be sure to release this if we ultimately decide - * not to process the table! - */ - if (!ConditionalLockRelationOid(index->indrelid, AccessShareLock)) - continue; - - /* Verify that the table still exists; skip if not */ classtup = SearchSysCache1(RELOID, ObjectIdGetDatum(index->indrelid)); if (!HeapTupleIsValid(classtup)) - { - UnlockRelationOid(index->indrelid, AccessShareLock); continue; - } classForm = (Form_pg_class) GETSTRUCT(classtup); /* Skip temp relations belonging to other sessions */ @@ -2192,7 +2179,6 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) !isTempOrTempToastNamespace(classForm->relnamespace)) { ReleaseSysCache(classtup); - UnlockRelationOid(index->indrelid, AccessShareLock); continue; } @@ -2201,10 +2187,7 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) /* noisily skip rels which the user can't process */ if (!repack_is_permitted_for_relation(cmd, index->indrelid, GetUserId())) - { - UnlockRelationOid(index->indrelid, AccessShareLock); continue; - } /* Use a permanent memory context for the result list */ oldcxt = MemoryContextSwitchTo(permcxt); @@ -2228,45 +2211,20 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) class = (Form_pg_class) GETSTRUCT(tuple); - /* - * Try to obtain a light lock on the table, to ensure it doesn't - * go away while we collect the list. If we cannot, just - * disregard the table. Be sure to release this if we ultimately - * decide not to process the table! - */ - if (!ConditionalLockRelationOid(class->oid, AccessShareLock)) - continue; - - /* Verify that the table still exists */ - if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(class->oid))) - { - UnlockRelationOid(class->oid, AccessShareLock); - continue; - } - /* Can only process plain tables and matviews */ if (class->relkind != RELKIND_RELATION && class->relkind != RELKIND_MATVIEW) - { - UnlockRelationOid(class->oid, AccessShareLock); continue; - } /* Skip temp relations belonging to other sessions */ if (class->relpersistence == RELPERSISTENCE_TEMP && !isTempOrTempToastNamespace(class->relnamespace)) - { - UnlockRelationOid(class->oid, AccessShareLock); continue; - } /* noisily skip rels which the user can't process */ if (!repack_is_permitted_for_relation(cmd, class->oid, GetUserId())) - { - UnlockRelationOid(class->oid, AccessShareLock); continue; - } /* Use a permanent memory context for the result list */ oldcxt = MemoryContextSwitchTo(permcxt); @@ -2279,7 +2237,7 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) } table_endscan(scan); - relation_close(catalog, AccessShareLock); + table_close(catalog, AccessShareLock); return rtcs; } @@ -2357,15 +2315,28 @@ get_tables_to_repack_partitioned(RepackCommand cmd, Oid relid, static bool repack_is_permitted_for_relation(RepackCommand cmd, Oid relid, Oid userid) { + bool is_missing = false; + Assert(cmd == REPACK_COMMAND_CLUSTER || cmd == REPACK_COMMAND_REPACK); - if (pg_class_aclcheck(relid, userid, ACL_MAINTAIN) == ACLCHECK_OK) + if (pg_class_aclcheck_ext(relid, userid, ACL_MAINTAIN, &is_missing) == ACLCHECK_OK) return true; - ereport(WARNING, - errmsg("permission denied to execute %s on \"%s\", skipping it", - RepackCommandAsString(cmd), - get_rel_name(relid))); + /* Report a warning if the relation still exists. */ + if (!is_missing) + { + char *relname; + + relname = get_rel_name(relid); + if (relname != NULL) + { + ereport(WARNING, + errmsg("permission denied to execute %s on \"%s\", skipping it", + RepackCommandAsString(cmd), relname)); + + pfree(relname); + } + } return false; } -- 2.47.3 --op6mnexl7cn72cto Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename=v2-0002-fixups.patch ^ permalink raw reply [nested|flat] 11+ messages in thread
* [PATCH v2 1/2] Do not lock tables in get_tables_to_repack(). @ 2026-06-16 06:49 ChangAo Chen <[email protected]> 0 siblings, 0 replies; 11+ messages in thread From: ChangAo Chen @ 2026-06-16 06:49 UTC (permalink / raw) When doing a whole database repack, we build a list of repackable tables and take a lock on them to prevent concurrent drops. But concurrent drops can always happen after we build the list because we process each table in a separate transaction. The ConditionalLockRelationOid() also makes the default behavior like SKIP_LOCKED, which is unexpected. To remove the locks, we need to make repack_is_permitted_for_relation() handles concurrent drops correctly: it should not report an error when failing to search the syscache in pg_class_aclcheck(). Use pg_class_aclcheck_ext() instead to detect a concurrent drop. Also check the return value of get_rel_name(). While at it, replace relation_close() with table_close() to match the table_open(). --- src/backend/commands/repack.c | 67 ++++++++++------------------------- 1 file changed, 19 insertions(+), 48 deletions(-) diff --git a/src/backend/commands/repack.c b/src/backend/commands/repack.c index faa07d1a118..2879c8af574 100644 --- a/src/backend/commands/repack.c +++ b/src/backend/commands/repack.c @@ -2169,22 +2169,9 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) index = (Form_pg_index) GETSTRUCT(tuple); - /* - * Try to obtain a light lock on the index's table, to ensure it - * doesn't go away while we collect the list. If we cannot, just - * disregard it. Be sure to release this if we ultimately decide - * not to process the table! - */ - if (!ConditionalLockRelationOid(index->indrelid, AccessShareLock)) - continue; - - /* Verify that the table still exists; skip if not */ classtup = SearchSysCache1(RELOID, ObjectIdGetDatum(index->indrelid)); if (!HeapTupleIsValid(classtup)) - { - UnlockRelationOid(index->indrelid, AccessShareLock); continue; - } classForm = (Form_pg_class) GETSTRUCT(classtup); /* Skip temp relations belonging to other sessions */ @@ -2192,7 +2179,6 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) !isTempOrTempToastNamespace(classForm->relnamespace)) { ReleaseSysCache(classtup); - UnlockRelationOid(index->indrelid, AccessShareLock); continue; } @@ -2201,10 +2187,7 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) /* noisily skip rels which the user can't process */ if (!repack_is_permitted_for_relation(cmd, index->indrelid, GetUserId())) - { - UnlockRelationOid(index->indrelid, AccessShareLock); continue; - } /* Use a permanent memory context for the result list */ oldcxt = MemoryContextSwitchTo(permcxt); @@ -2228,45 +2211,20 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) class = (Form_pg_class) GETSTRUCT(tuple); - /* - * Try to obtain a light lock on the table, to ensure it doesn't - * go away while we collect the list. If we cannot, just - * disregard the table. Be sure to release this if we ultimately - * decide not to process the table! - */ - if (!ConditionalLockRelationOid(class->oid, AccessShareLock)) - continue; - - /* Verify that the table still exists */ - if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(class->oid))) - { - UnlockRelationOid(class->oid, AccessShareLock); - continue; - } - /* Can only process plain tables and matviews */ if (class->relkind != RELKIND_RELATION && class->relkind != RELKIND_MATVIEW) - { - UnlockRelationOid(class->oid, AccessShareLock); continue; - } /* Skip temp relations belonging to other sessions */ if (class->relpersistence == RELPERSISTENCE_TEMP && !isTempOrTempToastNamespace(class->relnamespace)) - { - UnlockRelationOid(class->oid, AccessShareLock); continue; - } /* noisily skip rels which the user can't process */ if (!repack_is_permitted_for_relation(cmd, class->oid, GetUserId())) - { - UnlockRelationOid(class->oid, AccessShareLock); continue; - } /* Use a permanent memory context for the result list */ oldcxt = MemoryContextSwitchTo(permcxt); @@ -2279,7 +2237,7 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) } table_endscan(scan); - relation_close(catalog, AccessShareLock); + table_close(catalog, AccessShareLock); return rtcs; } @@ -2357,15 +2315,28 @@ get_tables_to_repack_partitioned(RepackCommand cmd, Oid relid, static bool repack_is_permitted_for_relation(RepackCommand cmd, Oid relid, Oid userid) { + bool is_missing = false; + Assert(cmd == REPACK_COMMAND_CLUSTER || cmd == REPACK_COMMAND_REPACK); - if (pg_class_aclcheck(relid, userid, ACL_MAINTAIN) == ACLCHECK_OK) + if (pg_class_aclcheck_ext(relid, userid, ACL_MAINTAIN, &is_missing) == ACLCHECK_OK) return true; - ereport(WARNING, - errmsg("permission denied to execute %s on \"%s\", skipping it", - RepackCommandAsString(cmd), - get_rel_name(relid))); + /* Report a warning if the relation still exists. */ + if (!is_missing) + { + char *relname; + + relname = get_rel_name(relid); + if (relname != NULL) + { + ereport(WARNING, + errmsg("permission denied to execute %s on \"%s\", skipping it", + RepackCommandAsString(cmd), relname)); + + pfree(relname); + } + } return false; } -- 2.47.3 --op6mnexl7cn72cto Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename=v2-0002-fixups.patch ^ permalink raw reply [nested|flat] 11+ messages in thread
* [PATCH v2 1/2] Do not lock tables in get_tables_to_repack(). @ 2026-06-16 06:49 ChangAo Chen <[email protected]> 0 siblings, 0 replies; 11+ messages in thread From: ChangAo Chen @ 2026-06-16 06:49 UTC (permalink / raw) When doing a whole database repack, we build a list of repackable tables and take a lock on them to prevent concurrent drops. But concurrent drops can always happen after we build the list because we process each table in a separate transaction. The ConditionalLockRelationOid() also makes the default behavior like SKIP_LOCKED, which is unexpected. To remove the locks, we need to make repack_is_permitted_for_relation() handles concurrent drops correctly: it should not report an error when failing to search the syscache in pg_class_aclcheck(). Use pg_class_aclcheck_ext() instead to detect a concurrent drop. Also check the return value of get_rel_name(). While at it, replace relation_close() with table_close() to match the table_open(). --- src/backend/commands/repack.c | 67 ++++++++++------------------------- 1 file changed, 19 insertions(+), 48 deletions(-) diff --git a/src/backend/commands/repack.c b/src/backend/commands/repack.c index faa07d1a118..2879c8af574 100644 --- a/src/backend/commands/repack.c +++ b/src/backend/commands/repack.c @@ -2169,22 +2169,9 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) index = (Form_pg_index) GETSTRUCT(tuple); - /* - * Try to obtain a light lock on the index's table, to ensure it - * doesn't go away while we collect the list. If we cannot, just - * disregard it. Be sure to release this if we ultimately decide - * not to process the table! - */ - if (!ConditionalLockRelationOid(index->indrelid, AccessShareLock)) - continue; - - /* Verify that the table still exists; skip if not */ classtup = SearchSysCache1(RELOID, ObjectIdGetDatum(index->indrelid)); if (!HeapTupleIsValid(classtup)) - { - UnlockRelationOid(index->indrelid, AccessShareLock); continue; - } classForm = (Form_pg_class) GETSTRUCT(classtup); /* Skip temp relations belonging to other sessions */ @@ -2192,7 +2179,6 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) !isTempOrTempToastNamespace(classForm->relnamespace)) { ReleaseSysCache(classtup); - UnlockRelationOid(index->indrelid, AccessShareLock); continue; } @@ -2201,10 +2187,7 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) /* noisily skip rels which the user can't process */ if (!repack_is_permitted_for_relation(cmd, index->indrelid, GetUserId())) - { - UnlockRelationOid(index->indrelid, AccessShareLock); continue; - } /* Use a permanent memory context for the result list */ oldcxt = MemoryContextSwitchTo(permcxt); @@ -2228,45 +2211,20 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) class = (Form_pg_class) GETSTRUCT(tuple); - /* - * Try to obtain a light lock on the table, to ensure it doesn't - * go away while we collect the list. If we cannot, just - * disregard the table. Be sure to release this if we ultimately - * decide not to process the table! - */ - if (!ConditionalLockRelationOid(class->oid, AccessShareLock)) - continue; - - /* Verify that the table still exists */ - if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(class->oid))) - { - UnlockRelationOid(class->oid, AccessShareLock); - continue; - } - /* Can only process plain tables and matviews */ if (class->relkind != RELKIND_RELATION && class->relkind != RELKIND_MATVIEW) - { - UnlockRelationOid(class->oid, AccessShareLock); continue; - } /* Skip temp relations belonging to other sessions */ if (class->relpersistence == RELPERSISTENCE_TEMP && !isTempOrTempToastNamespace(class->relnamespace)) - { - UnlockRelationOid(class->oid, AccessShareLock); continue; - } /* noisily skip rels which the user can't process */ if (!repack_is_permitted_for_relation(cmd, class->oid, GetUserId())) - { - UnlockRelationOid(class->oid, AccessShareLock); continue; - } /* Use a permanent memory context for the result list */ oldcxt = MemoryContextSwitchTo(permcxt); @@ -2279,7 +2237,7 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) } table_endscan(scan); - relation_close(catalog, AccessShareLock); + table_close(catalog, AccessShareLock); return rtcs; } @@ -2357,15 +2315,28 @@ get_tables_to_repack_partitioned(RepackCommand cmd, Oid relid, static bool repack_is_permitted_for_relation(RepackCommand cmd, Oid relid, Oid userid) { + bool is_missing = false; + Assert(cmd == REPACK_COMMAND_CLUSTER || cmd == REPACK_COMMAND_REPACK); - if (pg_class_aclcheck(relid, userid, ACL_MAINTAIN) == ACLCHECK_OK) + if (pg_class_aclcheck_ext(relid, userid, ACL_MAINTAIN, &is_missing) == ACLCHECK_OK) return true; - ereport(WARNING, - errmsg("permission denied to execute %s on \"%s\", skipping it", - RepackCommandAsString(cmd), - get_rel_name(relid))); + /* Report a warning if the relation still exists. */ + if (!is_missing) + { + char *relname; + + relname = get_rel_name(relid); + if (relname != NULL) + { + ereport(WARNING, + errmsg("permission denied to execute %s on \"%s\", skipping it", + RepackCommandAsString(cmd), relname)); + + pfree(relname); + } + } return false; } -- 2.47.3 --op6mnexl7cn72cto Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename=v2-0002-fixups.patch ^ permalink raw reply [nested|flat] 11+ messages in thread
* [PATCH v2 1/2] Do not lock tables in get_tables_to_repack(). @ 2026-06-16 06:49 ChangAo Chen <[email protected]> 0 siblings, 0 replies; 11+ messages in thread From: ChangAo Chen @ 2026-06-16 06:49 UTC (permalink / raw) When doing a whole database repack, we build a list of repackable tables and take a lock on them to prevent concurrent drops. But concurrent drops can always happen after we build the list because we process each table in a separate transaction. The ConditionalLockRelationOid() also makes the default behavior like SKIP_LOCKED, which is unexpected. To remove the locks, we need to make repack_is_permitted_for_relation() handles concurrent drops correctly: it should not report an error when failing to search the syscache in pg_class_aclcheck(). Use pg_class_aclcheck_ext() instead to detect a concurrent drop. Also check the return value of get_rel_name(). While at it, replace relation_close() with table_close() to match the table_open(). --- src/backend/commands/repack.c | 67 ++++++++++------------------------- 1 file changed, 19 insertions(+), 48 deletions(-) diff --git a/src/backend/commands/repack.c b/src/backend/commands/repack.c index faa07d1a118..2879c8af574 100644 --- a/src/backend/commands/repack.c +++ b/src/backend/commands/repack.c @@ -2169,22 +2169,9 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) index = (Form_pg_index) GETSTRUCT(tuple); - /* - * Try to obtain a light lock on the index's table, to ensure it - * doesn't go away while we collect the list. If we cannot, just - * disregard it. Be sure to release this if we ultimately decide - * not to process the table! - */ - if (!ConditionalLockRelationOid(index->indrelid, AccessShareLock)) - continue; - - /* Verify that the table still exists; skip if not */ classtup = SearchSysCache1(RELOID, ObjectIdGetDatum(index->indrelid)); if (!HeapTupleIsValid(classtup)) - { - UnlockRelationOid(index->indrelid, AccessShareLock); continue; - } classForm = (Form_pg_class) GETSTRUCT(classtup); /* Skip temp relations belonging to other sessions */ @@ -2192,7 +2179,6 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) !isTempOrTempToastNamespace(classForm->relnamespace)) { ReleaseSysCache(classtup); - UnlockRelationOid(index->indrelid, AccessShareLock); continue; } @@ -2201,10 +2187,7 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) /* noisily skip rels which the user can't process */ if (!repack_is_permitted_for_relation(cmd, index->indrelid, GetUserId())) - { - UnlockRelationOid(index->indrelid, AccessShareLock); continue; - } /* Use a permanent memory context for the result list */ oldcxt = MemoryContextSwitchTo(permcxt); @@ -2228,45 +2211,20 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) class = (Form_pg_class) GETSTRUCT(tuple); - /* - * Try to obtain a light lock on the table, to ensure it doesn't - * go away while we collect the list. If we cannot, just - * disregard the table. Be sure to release this if we ultimately - * decide not to process the table! - */ - if (!ConditionalLockRelationOid(class->oid, AccessShareLock)) - continue; - - /* Verify that the table still exists */ - if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(class->oid))) - { - UnlockRelationOid(class->oid, AccessShareLock); - continue; - } - /* Can only process plain tables and matviews */ if (class->relkind != RELKIND_RELATION && class->relkind != RELKIND_MATVIEW) - { - UnlockRelationOid(class->oid, AccessShareLock); continue; - } /* Skip temp relations belonging to other sessions */ if (class->relpersistence == RELPERSISTENCE_TEMP && !isTempOrTempToastNamespace(class->relnamespace)) - { - UnlockRelationOid(class->oid, AccessShareLock); continue; - } /* noisily skip rels which the user can't process */ if (!repack_is_permitted_for_relation(cmd, class->oid, GetUserId())) - { - UnlockRelationOid(class->oid, AccessShareLock); continue; - } /* Use a permanent memory context for the result list */ oldcxt = MemoryContextSwitchTo(permcxt); @@ -2279,7 +2237,7 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) } table_endscan(scan); - relation_close(catalog, AccessShareLock); + table_close(catalog, AccessShareLock); return rtcs; } @@ -2357,15 +2315,28 @@ get_tables_to_repack_partitioned(RepackCommand cmd, Oid relid, static bool repack_is_permitted_for_relation(RepackCommand cmd, Oid relid, Oid userid) { + bool is_missing = false; + Assert(cmd == REPACK_COMMAND_CLUSTER || cmd == REPACK_COMMAND_REPACK); - if (pg_class_aclcheck(relid, userid, ACL_MAINTAIN) == ACLCHECK_OK) + if (pg_class_aclcheck_ext(relid, userid, ACL_MAINTAIN, &is_missing) == ACLCHECK_OK) return true; - ereport(WARNING, - errmsg("permission denied to execute %s on \"%s\", skipping it", - RepackCommandAsString(cmd), - get_rel_name(relid))); + /* Report a warning if the relation still exists. */ + if (!is_missing) + { + char *relname; + + relname = get_rel_name(relid); + if (relname != NULL) + { + ereport(WARNING, + errmsg("permission denied to execute %s on \"%s\", skipping it", + RepackCommandAsString(cmd), relname)); + + pfree(relname); + } + } return false; } -- 2.47.3 --op6mnexl7cn72cto Content-Type: text/x-diff; charset=utf-8 Content-Disposition: attachment; filename=v2-0002-fixups.patch ^ permalink raw reply [nested|flat] 11+ messages in thread
* Do not lock tables in get_tables_to_repack @ 2026-06-16 07:34 =?utf-8?B?Y2NhNTUwNw==?= <[email protected]> 0 siblings, 2 replies; 11+ messages in thread From: =?utf-8?B?Y2NhNTUwNw==?= @ 2026-06-16 07:34 UTC (permalink / raw) To: =?utf-8?B?cGdzcWwtaGFja2Vycw==?= <[email protected]> Hi hackers, When doing a whole database repack, we build a list of repackable tables and take a lock on them to prevent concurrent drops. But concurrent drops can always happen after we build the list because we process each table in a separate transaction. The ConditionalLockRelationOid() also makes the default behavior like SKIP_LOCKED, which is unexpected. To remove the locks, we need to make repack_is_permitted_for_relation() handles concurrent drops correctly: it should not report an error when failing to search the syscache in pg_class_aclcheck(). Use pg_class_aclcheck_ext() instead to detect a concurrent drop. Also check the return value of get_rel_name(). Thoughts? -- Regards, ChangAo Chen Attachments: [application/octet-stream] v1-0001-Do-not-lock-tables-in-get_tables_to_repack.patch (5.4K, ../../[email protected]/2-v1-0001-Do-not-lock-tables-in-get_tables_to_repack.patch) download | inline diff: From fa5c3073f2f41cf3c8ab7c9663b681e6140a4824 Mon Sep 17 00:00:00 2001 From: ChangAo Chen <[email protected]> Date: Tue, 16 Jun 2026 14:49:49 +0800 Subject: [PATCH v1] Do not lock tables in get_tables_to_repack(). When doing a whole database repack, we build a list of repackable tables and take a lock on them to prevent concurrent drops. But concurrent drops can always happen after we build the list because we process each table in a separate transaction. The ConditionalLockRelationOid() also makes the default behavior like SKIP_LOCKED, which is unexpected. To remove the locks, we need to make repack_is_permitted_for_relation() handles concurrent drops correctly: it should not report an error when failing to search the syscache in pg_class_aclcheck(). Use pg_class_aclcheck_ext() instead to detect a concurrent drop. Also check the return value of get_rel_name(). While at it, replace relation_close() with table_close() to match the table_open(). --- src/backend/commands/repack.c | 67 ++++++++++------------------------- 1 file changed, 19 insertions(+), 48 deletions(-) diff --git a/src/backend/commands/repack.c b/src/backend/commands/repack.c index ec100e3eef5..6f25effeed2 100644 --- a/src/backend/commands/repack.c +++ b/src/backend/commands/repack.c @@ -2159,22 +2159,9 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) index = (Form_pg_index) GETSTRUCT(tuple); - /* - * Try to obtain a light lock on the index's table, to ensure it - * doesn't go away while we collect the list. If we cannot, just - * disregard it. Be sure to release this if we ultimately decide - * not to process the table! - */ - if (!ConditionalLockRelationOid(index->indrelid, AccessShareLock)) - continue; - - /* Verify that the table still exists; skip if not */ classtup = SearchSysCache1(RELOID, ObjectIdGetDatum(index->indrelid)); if (!HeapTupleIsValid(classtup)) - { - UnlockRelationOid(index->indrelid, AccessShareLock); continue; - } classForm = (Form_pg_class) GETSTRUCT(classtup); /* Skip temp relations belonging to other sessions */ @@ -2182,7 +2169,6 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) !isTempOrTempToastNamespace(classForm->relnamespace)) { ReleaseSysCache(classtup); - UnlockRelationOid(index->indrelid, AccessShareLock); continue; } @@ -2191,10 +2177,7 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) /* noisily skip rels which the user can't process */ if (!repack_is_permitted_for_relation(cmd, index->indrelid, GetUserId())) - { - UnlockRelationOid(index->indrelid, AccessShareLock); continue; - } /* Use a permanent memory context for the result list */ oldcxt = MemoryContextSwitchTo(permcxt); @@ -2218,45 +2201,20 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) class = (Form_pg_class) GETSTRUCT(tuple); - /* - * Try to obtain a light lock on the table, to ensure it doesn't - * go away while we collect the list. If we cannot, just - * disregard the table. Be sure to release this if we ultimately - * decide not to process the table! - */ - if (!ConditionalLockRelationOid(class->oid, AccessShareLock)) - continue; - - /* Verify that the table still exists */ - if (!SearchSysCacheExists1(RELOID, ObjectIdGetDatum(class->oid))) - { - UnlockRelationOid(class->oid, AccessShareLock); - continue; - } - /* Can only process plain tables and matviews */ if (class->relkind != RELKIND_RELATION && class->relkind != RELKIND_MATVIEW) - { - UnlockRelationOid(class->oid, AccessShareLock); continue; - } /* Skip temp relations belonging to other sessions */ if (class->relpersistence == RELPERSISTENCE_TEMP && !isTempOrTempToastNamespace(class->relnamespace)) - { - UnlockRelationOid(class->oid, AccessShareLock); continue; - } /* noisily skip rels which the user can't process */ if (!repack_is_permitted_for_relation(cmd, class->oid, GetUserId())) - { - UnlockRelationOid(class->oid, AccessShareLock); continue; - } /* Use a permanent memory context for the result list */ oldcxt = MemoryContextSwitchTo(permcxt); @@ -2269,7 +2227,7 @@ get_tables_to_repack(RepackCommand cmd, bool usingindex, MemoryContext permcxt) } table_endscan(scan); - relation_close(catalog, AccessShareLock); + table_close(catalog, AccessShareLock); return rtcs; } @@ -2347,15 +2305,28 @@ get_tables_to_repack_partitioned(RepackCommand cmd, Oid relid, static bool repack_is_permitted_for_relation(RepackCommand cmd, Oid relid, Oid userid) { + bool is_missing = false; + Assert(cmd == REPACK_COMMAND_CLUSTER || cmd == REPACK_COMMAND_REPACK); - if (pg_class_aclcheck(relid, userid, ACL_MAINTAIN) == ACLCHECK_OK) + if (pg_class_aclcheck_ext(relid, userid, ACL_MAINTAIN, &is_missing) == ACLCHECK_OK) return true; - ereport(WARNING, - errmsg("permission denied to execute %s on \"%s\", skipping it", - RepackCommandAsString(cmd), - get_rel_name(relid))); + /* Report a warning if the relation still exists. */ + if (!is_missing) + { + char *relname; + + relname = get_rel_name(relid); + if (relname != NULL) + { + ereport(WARNING, + errmsg("permission denied to execute %s on \"%s\", skipping it", + RepackCommandAsString(cmd), relname)); + + pfree(relname); + } + } return false; } -- 2.34.1 ^ permalink raw reply [nested|flat] 11+ messages in thread
* Re: Do not lock tables in get_tables_to_repack @ 2026-06-27 19:56 Bharath Rupireddy <[email protected]> parent: =?utf-8?B?Y2NhNTUwNw==?= <[email protected]> 1 sibling, 0 replies; 11+ messages in thread From: Bharath Rupireddy @ 2026-06-27 19:56 UTC (permalink / raw) To: cca5507 <[email protected]>; +Cc: pgsql-hackers <[email protected]>; Antonin Houska <[email protected]>; Alvaro Herrera <[email protected]> Hi, On Tue, Jun 16, 2026 at 12:35 AM cca5507 <[email protected]> wrote: > > Hi hackers, > > When doing a whole database repack, we build a list of repackable > tables and take a lock on them to prevent concurrent drops. But > concurrent drops can always happen after we build the list because > we process each table in a separate transaction. The > ConditionalLockRelationOid() also makes the default behavior like > SKIP_LOCKED, which is unexpected. > > To remove the locks, we need to make repack_is_permitted_for_relation() > handles concurrent drops correctly: it should not report an error > when failing to search the syscache in pg_class_aclcheck(). Use > pg_class_aclcheck_ext() instead to detect a concurrent drop. Also > check the return value of get_rel_name(). > > Thoughts? I don't have a strong opinion on fixing this for REPACK. For vacuum, we wanted to get consistent behavior across all modes of invoking it [1]. Whether to handle concurrent drops for REPACK depends on how long it spends scanning pg_index/pg_class in get_tables_to_repack. Also, vacuum is more commonly run database-wide (against all tables), and without field experience showing this is a real problem for REPACK, I'm not sure the fix is needed. That said, others may have a different take - adding the REPACK authors here for their input. [1] https://www.postgresql.org/message-id/CALj2ACUbhDFJWSwiyoUxXED2S2fr9Xis%3D08Rnjq53UzBE4FvzA%40mail.g... -- Bharath Rupireddy Amazon Web Services: https://aws.amazon.com ^ permalink raw reply [nested|flat] 11+ messages in thread
* Re: Do not lock tables in get_tables_to_repack @ 2026-07-07 16:53 Álvaro Herrera <[email protected]> parent: =?utf-8?B?Y2NhNTUwNw==?= <[email protected]> 1 sibling, 1 reply; 11+ messages in thread From: Álvaro Herrera @ 2026-07-07 16:53 UTC (permalink / raw) To: cca5507 <[email protected]>; +Cc: pgsql-hackers <[email protected]> On 2026-Jun-16, cca5507 wrote: > Hi hackers, > > When doing a whole database repack, we build a list of repackable > tables and take a lock on them to prevent concurrent drops. But > concurrent drops can always happen after we build the list because > we process each table in a separate transaction. Not only that. We have actually three ways to obtain the list of tables to repack, and only one of these obtains the locks. So this code is internally inconsistent. I agree that we should do something like your patch. I wanted to be a little more defensive though; how about the attached? -- Álvaro Herrera PostgreSQL Developer — https://www.EnterpriseDB.com/ ^ permalink raw reply [nested|flat] 11+ messages in thread
* Re: Do not lock tables in get_tables_to_repack @ 2026-07-08 02:36 =?utf-8?B?Y2NhNTUwNw==?= <[email protected]> parent: Álvaro Herrera <[email protected]> 0 siblings, 0 replies; 11+ messages in thread From: =?utf-8?B?Y2NhNTUwNw==?= @ 2026-07-08 02:36 UTC (permalink / raw) To: =?utf-8?B?w4FsdmFybyBIZXJyZXJh?= <[email protected]>; +Cc: =?utf-8?B?cGdzcWwtaGFja2Vycw==?= <[email protected]> > > Hi hackers, > > > > When doing a whole database repack, we build a list of repackable > > tables and take a lock on them to prevent concurrent drops. But > > concurrent drops can always happen after we build the list because > > we process each table in a separate transaction. > > Not only that. We have actually three ways to obtain the list of tables > to repack, and only one of these obtains the locks. So this code is > internally inconsistent. I agree that we should do something like your > patch. I wanted to be a little more defensive though; how about the > attached? - classtup = SearchSysCache1(RELOID, ObjectIdGetDatum(index->indrelid)); + classtup = SearchSysCacheCopy1(RELOID, ObjectIdGetDatum(index->indrelid)); Do we really need to copy it? We hold a refcount on it so it won't be freed until we release it. Otherwise LGTM. -- Regards, ChangAo Chen ^ permalink raw reply [nested|flat] 11+ messages in thread
end of thread, other threads:[~2026-07-08 02:36 UTC | newest] Thread overview: 11+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2026-06-16 06:49 [PATCH v2 1/2] Do not lock tables in get_tables_to_repack(). ChangAo Chen <[email protected]> 2026-06-16 06:49 [PATCH v2 1/2] Do not lock tables in get_tables_to_repack(). ChangAo Chen <[email protected]> 2026-06-16 06:49 [PATCH v2 1/2] Do not lock tables in get_tables_to_repack(). ChangAo Chen <[email protected]> 2026-06-16 06:49 [PATCH v2 1/2] Do not lock tables in get_tables_to_repack(). ChangAo Chen <[email protected]> 2026-06-16 06:49 [PATCH v2 1/2] Do not lock tables in get_tables_to_repack(). ChangAo Chen <[email protected]> 2026-06-16 06:49 [PATCH v2 1/2] Do not lock tables in get_tables_to_repack(). ChangAo Chen <[email protected]> 2026-06-16 06:49 [PATCH v2 1/2] Do not lock tables in get_tables_to_repack(). ChangAo Chen <[email protected]> 2026-06-16 07:34 Do not lock tables in get_tables_to_repack =?utf-8?B?Y2NhNTUwNw==?= <[email protected]> 2026-06-27 19:56 ` Re: Do not lock tables in get_tables_to_repack Bharath Rupireddy <[email protected]> 2026-07-07 16:53 ` Re: Do not lock tables in get_tables_to_repack Álvaro Herrera <[email protected]> 2026-07-08 02:36 ` Re: Do not lock tables in get_tables_to_repack =?utf-8?B?Y2NhNTUwNw==?= <[email protected]>
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