diff options
| -rw-r--r-- | src/backend/access/heap/heapam.c | 30 | ||||
| -rw-r--r-- | src/backend/access/heap/heapam_handler.c | 16 | ||||
| -rw-r--r-- | src/include/access/heapam.h | 2 |
3 files changed, 28 insertions, 20 deletions
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c index 8d7655f4cfd..74218510276 100644 --- a/src/backend/access/heap/heapam.c +++ b/src/backend/access/heap/heapam.c @@ -1530,10 +1530,14 @@ heap_getnextslot_tidrange(TableScanDesc sscan, ScanDirection direction, * must unpin the buffer when done with the tuple. * * If the tuple is not found (ie, item number references a deleted slot), - * then tuple->t_data is set to NULL and false is returned. + * then tuple->t_data is set to NULL, *userbuf is set to InvalidBuffer, + * and false is returned. * - * If the tuple is found but fails the time qual check, then false is returned - * but tuple->t_data is left pointing to the tuple. + * If the tuple is found but fails the time qual check, then the behavior + * depends on the keep_buf parameter. If keep_buf is false, the results + * are the same as for the tuple-not-found case. If keep_buf is true, + * then tuple->t_data and *userbuf are returned as for the success case, + * and again the caller must unpin the buffer; but false is returned. * * heap_fetch does not follow HOT chains: only the exact TID requested will * be fetched. @@ -1551,7 +1555,8 @@ bool heap_fetch(Relation relation, Snapshot snapshot, HeapTuple tuple, - Buffer *userbuf) + Buffer *userbuf, + bool keep_buf) { ItemPointer tid = &(tuple->t_self); ItemId lp; @@ -1634,9 +1639,15 @@ heap_fetch(Relation relation, return true; } - /* Tuple failed time qual */ - ReleaseBuffer(buffer); - *userbuf = InvalidBuffer; + /* Tuple failed time qual, but maybe caller wants to see it anyway. */ + if (keep_buf) + *userbuf = buffer; + else + { + ReleaseBuffer(buffer); + *userbuf = InvalidBuffer; + tuple->t_data = NULL; + } return false; } @@ -1659,8 +1670,7 @@ heap_fetch(Relation relation, * are vacuumable, false if not. * * Unlike heap_fetch, the caller must already have pin and (at least) share - * lock on the buffer; it is still pinned/locked at exit. Also unlike - * heap_fetch, we do not report any pgstats count; caller may do so if wanted. + * lock on the buffer; it is still pinned/locked at exit. */ bool heap_hot_search_buffer(ItemPointer tid, Relation relation, Buffer buffer, @@ -5379,7 +5389,7 @@ heap_lock_updated_tuple_rec(Relation rel, ItemPointer tid, TransactionId xid, block = ItemPointerGetBlockNumber(&tupid); ItemPointerCopy(&tupid, &(mytup.t_self)); - if (!heap_fetch(rel, SnapshotAny, &mytup, &buf)) + if (!heap_fetch(rel, SnapshotAny, &mytup, &buf, false)) { /* * if we fail to find the updated version of the tuple, it's diff --git a/src/backend/access/heap/heapam_handler.c b/src/backend/access/heap/heapam_handler.c index 666b6205a7b..444f027149c 100644 --- a/src/backend/access/heap/heapam_handler.c +++ b/src/backend/access/heap/heapam_handler.c @@ -188,7 +188,7 @@ heapam_fetch_row_version(Relation relation, Assert(TTS_IS_BUFFERTUPLE(slot)); bslot->base.tupdata.t_self = *tid; - if (heap_fetch(relation, snapshot, &bslot->base.tupdata, &buffer)) + if (heap_fetch(relation, snapshot, &bslot->base.tupdata, &buffer, false)) { /* store in slot, transferring existing pin */ ExecStorePinnedBufferHeapTuple(&bslot->base.tupdata, slot, buffer); @@ -401,7 +401,7 @@ tuple_lock_retry: errmsg("tuple to be locked was already moved to another partition due to concurrent update"))); tuple->t_self = *tid; - if (heap_fetch(relation, &SnapshotDirty, tuple, &buffer)) + if (heap_fetch(relation, &SnapshotDirty, tuple, &buffer, true)) { /* * If xmin isn't what we're expecting, the slot must have @@ -500,6 +500,7 @@ tuple_lock_retry: */ if (tuple->t_data == NULL) { + Assert(!BufferIsValid(buffer)); return TM_Deleted; } @@ -509,8 +510,7 @@ tuple_lock_retry: if (!TransactionIdEquals(HeapTupleHeaderGetXmin(tuple->t_data), priorXmax)) { - if (BufferIsValid(buffer)) - ReleaseBuffer(buffer); + ReleaseBuffer(buffer); return TM_Deleted; } @@ -526,13 +526,12 @@ tuple_lock_retry: * * As above, it should be safe to examine xmax and t_ctid * without the buffer content lock, because they can't be - * changing. + * changing. We'd better hold a buffer pin though. */ if (ItemPointerEquals(&tuple->t_self, &tuple->t_data->t_ctid)) { /* deleted, so forget about it */ - if (BufferIsValid(buffer)) - ReleaseBuffer(buffer); + ReleaseBuffer(buffer); return TM_Deleted; } @@ -540,8 +539,7 @@ tuple_lock_retry: *tid = tuple->t_data->t_ctid; /* updated row should have xmin matching this xmax */ priorXmax = HeapTupleHeaderGetUpdateXid(tuple->t_data); - if (BufferIsValid(buffer)) - ReleaseBuffer(buffer); + ReleaseBuffer(buffer); /* loop back to fetch next in chain */ } } diff --git a/src/include/access/heapam.h b/src/include/access/heapam.h index 4403f01e130..5d7f7fd800e 100644 --- a/src/include/access/heapam.h +++ b/src/include/access/heapam.h @@ -133,7 +133,7 @@ extern bool heap_getnextslot_tidrange(TableScanDesc sscan, ScanDirection direction, TupleTableSlot *slot); extern bool heap_fetch(Relation relation, Snapshot snapshot, - HeapTuple tuple, Buffer *userbuf); + HeapTuple tuple, Buffer *userbuf, bool keep_buf); extern bool heap_hot_search_buffer(ItemPointer tid, Relation relation, Buffer buffer, Snapshot snapshot, HeapTuple heapTuple, bool *all_dead, bool first_call); |