diff options
Diffstat (limited to 'src/backend/access/heap/heapam.c')
| -rw-r--r-- | src/backend/access/heap/heapam.c | 99 |
1 files changed, 60 insertions, 39 deletions
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c index a8d7ca0c29f..e763823a166 100644 --- a/src/backend/access/heap/heapam.c +++ b/src/backend/access/heap/heapam.c @@ -8,7 +8,7 @@ * * * IDENTIFICATION - * $Header: /cvsroot/pgsql/src/backend/access/heap/heapam.c,v 1.135 2002/05/21 22:05:53 tgl Exp $ + * $Header: /cvsroot/pgsql/src/backend/access/heap/heapam.c,v 1.136 2002/05/24 18:57:55 tgl Exp $ * * * INTERFACE ROUTINES @@ -306,6 +306,8 @@ heapgettup(Relation relation, { if (ItemIdIsUsed(lpp)) { + bool valid; + tuple->t_datamcxt = NULL; tuple->t_data = (HeapTupleHeader) PageGetItem((Page) dp, lpp); tuple->t_len = ItemIdGetLength(lpp); @@ -315,8 +317,8 @@ heapgettup(Relation relation, * if current tuple qualifies, return it. */ HeapTupleSatisfies(tuple, relation, *buffer, (PageHeader) dp, - snapshot, nkeys, key); - if (tuple->t_data != NULL) + snapshot, nkeys, key, valid); + if (valid) { LockBuffer(*buffer, BUFFER_LOCK_UNLOCK); return; @@ -864,32 +866,37 @@ heap_getnext(HeapScanDesc scan, ScanDirection direction) return ((scan->rs_ctup.t_data == NULL) ? NULL : &(scan->rs_ctup)); } -/* ---------------- - * heap_fetch - retrieve tuple with given tid +/* + * heap_fetch - retrieve tuple with given tid * - * On entry, tuple->t_self is the TID to fetch. + * On entry, tuple->t_self is the TID to fetch. We pin the buffer holding + * the tuple, fill in the remaining fields of *tuple, and check the tuple + * against the specified snapshot. * - * If successful (ie, tuple found and passes snapshot time qual), - * then the rest of *tuple is filled in, and *userbuf is set to the - * buffer holding the tuple. A pin is obtained on the buffer; the - * caller must BufferRelease the buffer when done with the tuple. + * If successful (tuple passes snapshot time qual), then *userbuf is set to + * the buffer holding the tuple and TRUE is returned. The caller must + * unpin the buffer when done with the tuple. * - * If not successful, tuple->t_data is set to NULL and *userbuf is set to - * InvalidBuffer. - * ---------------- + * If the tuple fails the time qual check, then FALSE will be returned. + * When the caller specifies keep_buf = true, we retain the pin on the + * buffer and return it in *userbuf (so the caller can still access the + * tuple); when keep_buf = false, the pin is released and *userbuf is set + * to InvalidBuffer. */ -void +bool heap_fetch(Relation relation, Snapshot snapshot, HeapTuple tuple, Buffer *userbuf, + bool keep_buf, PgStat_Info *pgstat_info) { + ItemPointer tid = &(tuple->t_self); ItemId lp; Buffer buffer; PageHeader dp; - ItemPointer tid = &(tuple->t_self); OffsetNumber offnum; + bool valid; /* * increment access statistics @@ -901,14 +908,16 @@ heap_fetch(Relation relation, * get the buffer from the relation descriptor. Note that this does a * buffer pin. */ - buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(tid)); if (!BufferIsValid(buffer)) - elog(ERROR, "heap_fetch: %s relation: ReadBuffer(%ld) failed", + elog(ERROR, "heap_fetch: ReadBuffer(%s, %lu) failed", RelationGetRelationName(relation), - (long) ItemPointerGetBlockNumber(tid)); + (unsigned long) ItemPointerGetBlockNumber(tid)); + /* + * Need share lock on buffer to examine tuple commit status. + */ LockBuffer(buffer, BUFFER_LOCK_SHARE); /* @@ -921,38 +930,34 @@ heap_fetch(Relation relation, /* * more sanity checks */ - if (!ItemIdIsUsed(lp)) { LockBuffer(buffer, BUFFER_LOCK_UNLOCK); ReleaseBuffer(buffer); - *userbuf = InvalidBuffer; - tuple->t_datamcxt = NULL; - tuple->t_data = NULL; - return; + + elog(ERROR, "heap_fetch: invalid tuple id (%s, %lu, %u)", + RelationGetRelationName(relation), + (unsigned long) ItemPointerGetBlockNumber(tid), + offnum); } + /* + * fill in *tuple fields + */ tuple->t_datamcxt = NULL; tuple->t_data = (HeapTupleHeader) PageGetItem((Page) dp, lp); tuple->t_len = ItemIdGetLength(lp); tuple->t_tableOid = relation->rd_id; /* - * check time qualification of tid + * check time qualification of tuple, then release lock */ - HeapTupleSatisfies(tuple, relation, buffer, dp, - snapshot, 0, (ScanKey) NULL); + snapshot, 0, (ScanKey) NULL, valid); LockBuffer(buffer, BUFFER_LOCK_UNLOCK); - if (tuple->t_data == NULL) - { - /* Tuple failed time check, so we can release now. */ - ReleaseBuffer(buffer); - *userbuf = InvalidBuffer; - } - else + if (valid) { /* * All checks passed, so return the tuple as valid. Caller is now @@ -968,13 +973,28 @@ heap_fetch(Relation relation, pgstat_count_heap_fetch(pgstat_info); else pgstat_count_heap_fetch(&relation->pgstat_info); + + return true; } + + /* Tuple failed time qual, but maybe caller wants to see it anyway. */ + if (keep_buf) + { + *userbuf = buffer; + + return false; + } + + /* Okay to release pin on buffer. */ + ReleaseBuffer(buffer); + + *userbuf = InvalidBuffer; + + return false; } -/* ---------------- +/* * heap_get_latest_tid - get the latest tid of a specified tuple - * - * ---------------- */ ItemPointer heap_get_latest_tid(Relation relation, @@ -989,7 +1009,8 @@ heap_get_latest_tid(Relation relation, HeapTupleHeader t_data; ItemPointerData ctid; bool invalidBlock, - linkend; + linkend, + valid; /* * get the buffer from the relation descriptor Note that this does a @@ -1038,7 +1059,7 @@ heap_get_latest_tid(Relation relation, */ HeapTupleSatisfies(&tp, relation, buffer, dp, - snapshot, 0, (ScanKey) NULL); + snapshot, 0, (ScanKey) NULL, valid); linkend = true; if ((t_data->t_infomask & HEAP_XMIN_COMMITTED) != 0 && @@ -1048,7 +1069,7 @@ heap_get_latest_tid(Relation relation, LockBuffer(buffer, BUFFER_LOCK_UNLOCK); ReleaseBuffer(buffer); - if (tp.t_data == NULL) + if (!valid) { if (linkend) return NULL; |