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Teach heapam code to know the difference between a real seqscan and the

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pseudo HeapScanDesc created for a bitmap heap scan.  This avoids some useless
overhead during a bitmap scan startup, in particular invoking the syncscan
code.  (We might someday want to do that, but right now it's merely useless
contention for shared memory, to say nothing of possibly pushing useful
entries out of syncscan's small LRU list.)  This also allows elimination of
ugly pgstat_discount_heap_scan() kluge.
This commit is contained in:
Tom Lane
2007-06-09 18:49:55 +00:00
parent 7063c46fc1
commit 85d72f0516
5 changed files with 48 additions and 34 deletions
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4
src/include/access/heapam.h
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@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/access/heapam.h,v 1.125 2007/06/08 18:23:53 tgl Exp $
* $PostgreSQL: pgsql/src/include/access/heapam.h,v 1.126 2007/06/09 18:49:55 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -141,6 +141,8 @@ extern Relation heap_openrv(const RangeVar *relation, LOCKMODE lockmode);
extern HeapScanDesc heap_beginscan(Relation relation, Snapshot snapshot,
int nkeys, ScanKey key);
extern HeapScanDesc heap_beginscan_bm(Relation relation, Snapshot snapshot,
int nkeys, ScanKey key);
extern void heap_rescan(HeapScanDesc scan, ScanKey key);
extern void heap_endscan(HeapScanDesc scan);
extern HeapTuple heap_getnext(HeapScanDesc scan, ScanDirection direction);