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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 * 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 * INTERFACE ROUTINES
@ -102,7 +102,16 @@ initscan(HeapScanDesc scan,
unsigned nkeys, unsigned nkeys,
ScanKey key) 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 * relation is empty
@ -652,11 +661,12 @@ heap_beginscan(Relation relation,
*/ */
scan = (HeapScanDesc) palloc(sizeof(HeapScanDescData)); scan = (HeapScanDesc) palloc(sizeof(HeapScanDescData));
relation->rd_nblocks = smgrnblocks(DEFAULT_SMGR, relation);
scan->rs_rd = relation; scan->rs_rd = relation;
scan->rs_atend = atend;
scan->rs_snapshot = snapshot;
scan->rs_nkeys = (short) nkeys;
if (nkeys) if (nkeys)
/* /*
* we do this here instead of in initscan() because heap_rescan * we do this here instead of in initscan() because heap_rescan
* also calls initscan() and we don't want to allocate memory * 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); initscan(scan, relation, atend, nkeys, key);
scan->rs_atend = atend;
scan->rs_snapshot = snapshot;
scan->rs_nkeys = (short) nkeys;
return scan; return scan;
} }
@ -703,8 +709,8 @@ heap_rescan(HeapScanDesc scan,
* reinitialize scan descriptor * reinitialize scan descriptor
* ---------------- * ----------------
*/ */
initscan(scan, scan->rs_rd, scanFromEnd, scan->rs_nkeys, key);
scan->rs_atend = (bool) scanFromEnd; 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, Snapshot snapshot,
ItemPointer tid) ItemPointer tid)
{ {
ItemId lp; ItemId lp = NULL;
Buffer buffer; Buffer buffer;
PageHeader dp; PageHeader dp;
OffsetNumber offnum; OffsetNumber offnum;