public inbox for [email protected]
help / color / mirror / Atom feedFrom: ChangAo Chen <[email protected]>
Subject: [PATCH v2 1/2] Do not lock tables in get_tables_to_repack().
Date: Tue, 16 Jun 2026 14:49:49 +0800
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
view thread (11+ messages) latest in thread
reply
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: [email protected]
Cc: [email protected]
Subject: Re: [PATCH v2 1/2] Do not lock tables in get_tables_to_repack().
In-Reply-To: <no-message-id-1833401@localhost>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by agora; see mirroring instructions
for how to clone and mirror all data and code used for this inbox