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Rearrange heap_beginscan to eliminate extra call on

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mdnblocks.  Bad enough it does an lseek, but to do it twice for no
reason...
This commit is contained in:
Tom Lane 1999-10-30 23:10:21 +00:00
parent 57ea208477
commit 4ce4d7f7d3
1 changed files with 16 additions and 10 deletions
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26
src/backend/access/heap/heapam.c
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@ -7,7 +7,7 @@
*
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/access/heap/heapam.c,v 1.56 1999/10/11 06:28:27 inoue Exp $
* $Header: /cvsroot/pgsql/src/backend/access/heap/heapam.c,v 1.57 1999/10/30 23:10:21 tgl Exp $
*
*
* INTERFACE ROUTINES
@ -102,7 +102,16 @@ initscan(HeapScanDesc scan,
unsigned nkeys,
ScanKey key)
{
if (!RelationGetNumberOfBlocks(relation))
/* ----------------
* Make sure we have up-to-date idea of number of blocks in relation.
* It is sufficient to do this once at scan start, since any tuples
* added while the scan is in progress will be invisible to my
* transaction anyway...
* ----------------
*/
relation->rd_nblocks = RelationGetNumberOfBlocks(relation);
if (relation->rd_nblocks == 0)
{
/* ----------------
* relation is empty
@ -652,11 +661,12 @@ heap_beginscan(Relation relation,
*/
scan = (HeapScanDesc) palloc(sizeof(HeapScanDescData));
relation->rd_nblocks = smgrnblocks(DEFAULT_SMGR, relation);
scan->rs_rd = relation;
scan->rs_atend = atend;
scan->rs_snapshot = snapshot;
scan->rs_nkeys = (short) nkeys;
if (nkeys)
/*
* we do this here instead of in initscan() because heap_rescan
* also calls initscan() and we don't want to allocate memory
@ -668,10 +678,6 @@ heap_beginscan(Relation relation,
initscan(scan, relation, atend, nkeys, key);
scan->rs_atend = atend;
scan->rs_snapshot = snapshot;
scan->rs_nkeys = (short) nkeys;
return scan;
}
@ -703,8 +709,8 @@ heap_rescan(HeapScanDesc scan,
* reinitialize scan descriptor
* ----------------
*/
initscan(scan, scan->rs_rd, scanFromEnd, scan->rs_nkeys, key);
scan->rs_atend = (bool) scanFromEnd;
initscan(scan, scan->rs_rd, scanFromEnd, scan->rs_nkeys, key);
}
/* ----------------
@ -1096,7 +1102,7 @@ heap_get_latest_tid(Relation relation,
Snapshot snapshot,
ItemPointer tid)
{
ItemId lp;
ItemId lp = NULL;
Buffer buffer;
PageHeader dp;
OffsetNumber offnum;