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Don't clear btpo_cycleid during _bt_vacuum_one_page.

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When "vacuuming" a single btree page by removing LP_DEAD tuples, we are not
actually within a vacuum operation, but rather in an ordinary insertion
process that could well be running concurrently with a vacuum.  So clearing
the cycleid is incorrect, and could cause the concurrent vacuum to miss
removing tuples that it needs to remove.  This is a longstanding bug
introduced by commit e6284649b9e30372b3990107a082bc7520325676 of
2006-07-25.  I believe it explains Maxim Boguk's recent report of index
corruption, and probably some other previously unexplained reports.

In 9.0 and up this is a one-line fix; before that we need to introduce a
flag to tell _bt_delitems what to do.
This commit is contained in:
Tom Lane 2012-02-21 15:03:56 -05:00
parent a863963fcd
commit 7b6a37f5ec
4 changed files with 9 additions and 7 deletions
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2
src/backend/access/nbtree/nbtinsert.c
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@ -1978,7 +1978,7 @@ _bt_vacuum_one_page(Relation rel, Buffer buffer)
}
if (ndeletable > 0)
_bt_delitems(rel, buffer, deletable, ndeletable);
_bt_delitems(rel, buffer, deletable, ndeletable, false);
/*
* Note: if we didn't find any LP_DEAD items, then the page's

10
src/backend/access/nbtree/nbtpage.c
View File

@ -656,7 +656,8 @@ _bt_page_recyclable(Page page)
*/
void
_bt_delitems(Relation rel, Buffer buf,
OffsetNumber *itemnos, int nitems)
OffsetNumber *itemnos, int nitems,
bool inVacuum)
{
Page page = BufferGetPage(buf);
BTPageOpaque opaque;
@ -668,11 +669,12 @@ _bt_delitems(Relation rel, Buffer buf,
PageIndexMultiDelete(page, itemnos, nitems);
/*
* We can clear the vacuum cycle ID since this page has certainly been
* processed by the current vacuum scan.
* If this is within VACUUM, we can clear the vacuum cycle ID since this
* page has certainly been processed by the current vacuum scan.
*/
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
opaque->btpo_cycleid = 0;
if (inVacuum)
opaque->btpo_cycleid = 0;
/*
* Mark the page as not containing any LP_DEAD items. This is not

2
src/backend/access/nbtree/nbtree.c
View File

@ -857,7 +857,7 @@ restart:
*/
if (ndeletable > 0)
{
_bt_delitems(rel, buf, deletable, ndeletable);
_bt_delitems(rel, buf, deletable, ndeletable, true);
stats->tuples_removed += ndeletable;
/* must recompute maxoff */
maxoff = PageGetMaxOffsetNumber(page);

2
src/include/access/nbtree.h
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@ -537,7 +537,7 @@ extern void _bt_relbuf(Relation rel, Buffer buf);
extern void _bt_pageinit(Page page, Size size);
extern bool _bt_page_recyclable(Page page);
extern void _bt_delitems(Relation rel, Buffer buf,
OffsetNumber *itemnos, int nitems);
OffsetNumber *itemnos, int nitems, bool inVacuum);
extern int _bt_pagedel(Relation rel, Buffer buf,
BTStack stack, bool vacuum_full);