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Keep heap_page_prune from marking the buffer dirty when it didn't

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really change anything.  Per report from Itagaki Takahiro.  Fix by
Pavan Deolasee.
This commit is contained in:
Tom Lane
2007-10-24 13:05:57 +00:00
parent 1c92724985
commit 9226ba817b
1 changed files with 24 additions and 9 deletions
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29
src/backend/access/heap/pruneheap.c
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@ -8,7 +8,7 @@
* *
* *
* IDENTIFICATION * IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/heap/pruneheap.c,v 1.2 2007/09/21 21:25:42 tgl Exp $ * $PostgreSQL: pgsql/src/backend/access/heap/pruneheap.c,v 1.3 2007/10/24 13:05:57 tgl Exp $
* *
*------------------------------------------------------------------------- *-------------------------------------------------------------------------
*/ */
@ -146,17 +146,29 @@ heap_page_prune(Relation relation, Buffer buffer, TransactionId OldestXmin,
int nredirected = 0; int nredirected = 0;
int ndead = 0; int ndead = 0;
int nunused = 0; int nunused = 0;
bool page_was_full = false;
TransactionId save_prune_xid;
START_CRIT_SECTION(); START_CRIT_SECTION();
/* /*
* Mark the page as clear of prunable tuples. If we find a tuple which * Save the current pd_prune_xid and mark the page as clear of prunable
* may soon become prunable, we shall set the hint again. Also clear * tuples. If we find a tuple which may soon become prunable, we shall set
* the "page is full" flag, since there's no point in repeating the * the hint again.
* prune/defrag process until something else happens to the page.
*/ */
save_prune_xid = ((PageHeader) page)->pd_prune_xid;
PageClearPrunable(page); PageClearPrunable(page);
/*
* Also clear the "page is full" flag if it is set, since there's no point
* in repeating the prune/defrag process until something else happens to
* the page.
*/
if (PageIsFull(page))
{
PageClearFull(page); PageClearFull(page);
page_was_full = true;
}
/* Scan the page */ /* Scan the page */
maxoff = PageGetMaxOffsetNumber(page); maxoff = PageGetMaxOffsetNumber(page);
@ -209,9 +221,12 @@ heap_page_prune(Relation relation, Buffer buffer, TransactionId OldestXmin,
else else
{ {
/* /*
* If we didn't prune anything, we have nonetheless updated the * If we didn't prune anything, but have updated either the
* pd_prune_xid field; treat this as a non-WAL-logged hint. * pd_prune_xid field or the "page is full" flag, mark the buffer
* dirty. This is treated as a non-WAL-logged hint.
*/ */
if (((PageHeader) page)->pd_prune_xid != save_prune_xid ||
page_was_full)
SetBufferCommitInfoNeedsSave(buffer); SetBufferCommitInfoNeedsSave(buffer);
} }