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Improve handling of prune/no-prune decisions by storing a page's oldest

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unpruned XMAX in its header.  At the cost of 4 bytes per page, this keeps us
from performing heap_page_prune when there's no chance of pruning anything.
Seems to be necessary per Heikki's preliminary performance testing.
This commit is contained in:
Tom Lane
2007-09-21 21:25:42 +00:00
parent 386a5d4268
commit cc59049daf
10 changed files with 92 additions and 59 deletions
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5
src/backend/storage/page/bufpage.c
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@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/page/bufpage.c,v 1.74 2007/09/20 17:56:31 tgl Exp $
* $PostgreSQL: pgsql/src/backend/storage/page/bufpage.c,v 1.75 2007/09/21 21:25:42 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -40,11 +40,12 @@ PageInit(Page page, Size pageSize, Size specialSize)
/* Make sure all fields of page are zero, as well as unused space */
MemSet(p, 0, pageSize);
/* p->pd_flags = 0; done by above MemSet */
/* p->pd_flags = 0; done by above MemSet */
p->pd_lower = SizeOfPageHeaderData;
p->pd_upper = pageSize - specialSize;
p->pd_special = pageSize - specialSize;
PageSetPageSizeAndVersion(page, pageSize, PG_PAGE_LAYOUT_VERSION);
/* p->pd_prune_xid = InvalidTransactionId; done by above MemSet */
}