diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/access/heap/heapam_visibility.c | 9 | ||||
| -rw-r--r-- | src/backend/access/index/genam.c | 8 | ||||
| -rw-r--r-- | src/backend/commands/dbcommands.c | 3 | ||||
| -rw-r--r-- | src/backend/utils/cache/relcache.c | 15 | ||||
| -rw-r--r-- | src/backend/utils/time/snapmgr.c | 8 |
5 files changed, 26 insertions, 17 deletions
diff --git a/src/backend/access/heap/heapam_visibility.c b/src/backend/access/heap/heapam_visibility.c index e146605bd57..05f6946fe60 100644 --- a/src/backend/access/heap/heapam_visibility.c +++ b/src/backend/access/heap/heapam_visibility.c @@ -962,6 +962,15 @@ HeapTupleSatisfiesMVCC(HeapTuple htup, Snapshot snapshot, { HeapTupleHeader tuple = htup->t_data; + /* + * Assert that the caller has registered the snapshot. This function + * doesn't care about the registration as such, but in general you + * shouldn't try to use a snapshot without registration because it might + * get invalidated while it's still in use, and this is a convenient place + * to check for that. + */ + Assert(snapshot->regd_count > 0 || snapshot->active_count > 0); + Assert(ItemPointerIsValid(&htup->t_self)); Assert(htup->t_tableOid != InvalidOid); diff --git a/src/backend/access/index/genam.c b/src/backend/access/index/genam.c index 886c05655f4..8f532e14590 100644 --- a/src/backend/access/index/genam.c +++ b/src/backend/access/index/genam.c @@ -577,17 +577,13 @@ systable_recheck_tuple(SysScanDesc sysscan, HeapTuple tup) Assert(tup == ExecFetchSlotHeapTuple(sysscan->slot, false, NULL)); - /* - * Trust that table_tuple_satisfies_snapshot() and its subsidiaries - * (commonly LockBuffer() and HeapTupleSatisfiesMVCC()) do not themselves - * acquire snapshots, so we need not register the snapshot. Those - * facilities are too low-level to have any business scanning tables. - */ freshsnap = GetCatalogSnapshot(RelationGetRelid(sysscan->heap_rel)); + freshsnap = RegisterSnapshot(freshsnap); result = table_tuple_satisfies_snapshot(sysscan->heap_rel, sysscan->slot, freshsnap); + UnregisterSnapshot(freshsnap); /* * Handle the concurrent abort while fetching the catalog tuple during diff --git a/src/backend/commands/dbcommands.c b/src/backend/commands/dbcommands.c index 1753b289074..5fbbcdaabb1 100644 --- a/src/backend/commands/dbcommands.c +++ b/src/backend/commands/dbcommands.c @@ -288,7 +288,7 @@ ScanSourceDatabasePgClass(Oid tbid, Oid dbid, char *srcpath) * snapshot - or the active snapshot - might not be new enough for that, * but the return value of GetLatestSnapshot() should work fine. */ - snapshot = GetLatestSnapshot(); + snapshot = RegisterSnapshot(GetLatestSnapshot()); /* Process the relation block by block. */ for (blkno = 0; blkno < nblocks; blkno++) @@ -313,6 +313,7 @@ ScanSourceDatabasePgClass(Oid tbid, Oid dbid, char *srcpath) UnlockReleaseBuffer(buf); } + UnregisterSnapshot(snapshot); /* Release relation lock. */ UnlockRelationId(&relid, AccessShareLock); diff --git a/src/backend/utils/cache/relcache.c b/src/backend/utils/cache/relcache.c index d1ae761b3f6..9f54a9e72b7 100644 --- a/src/backend/utils/cache/relcache.c +++ b/src/backend/utils/cache/relcache.c @@ -371,14 +371,13 @@ ScanPgRelation(Oid targetRelId, bool indexOK, bool force_non_historic) pg_class_desc = table_open(RelationRelationId, AccessShareLock); /* - * The caller might need a tuple that's newer than the one the historic - * snapshot; currently the only case requiring to do so is looking up the - * relfilenumber of non mapped system relations during decoding. That - * snapshot can't change in the midst of a relcache build, so there's no - * need to register the snapshot. + * The caller might need a tuple that's newer than what's visible to the + * historic snapshot; currently the only case requiring to do so is + * looking up the relfilenumber of non mapped system relations during + * decoding. */ if (force_non_historic) - snapshot = GetNonHistoricCatalogSnapshot(RelationRelationId); + snapshot = RegisterSnapshot(GetNonHistoricCatalogSnapshot(RelationRelationId)); pg_class_scan = systable_beginscan(pg_class_desc, ClassOidIndexId, indexOK && criticalRelcachesBuilt, @@ -395,6 +394,10 @@ ScanPgRelation(Oid targetRelId, bool indexOK, bool force_non_historic) /* all done */ systable_endscan(pg_class_scan); + + if (snapshot) + UnregisterSnapshot(snapshot); + table_close(pg_class_desc, AccessShareLock); return pg_class_tuple; diff --git a/src/backend/utils/time/snapmgr.c b/src/backend/utils/time/snapmgr.c index 8f1508b1ee2..6ed1c93383e 100644 --- a/src/backend/utils/time/snapmgr.c +++ b/src/backend/utils/time/snapmgr.c @@ -203,10 +203,10 @@ typedef struct SerializedSnapshotData * GetTransactionSnapshot * Get the appropriate snapshot for a new query in a transaction. * - * Note that the return value may point at static storage that will be modified - * by future calls and by CommandCounterIncrement(). Callers should call - * RegisterSnapshot or PushActiveSnapshot on the returned snap if it is to be - * used very long. + * Note that the return value points at static storage that will be modified + * by future calls and by CommandCounterIncrement(). Callers must call + * RegisterSnapshot or PushActiveSnapshot on the returned snap before doing + * any other non-trivial work that could invalidate it. */ Snapshot GetTransactionSnapshot(void) |