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HOT updates. When we update a tuple without changing any of its indexed

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columns, and the new version can be stored on the same heap page, we no longer
generate extra index entries for the new version.  Instead, index searches
follow the HOT-chain links to ensure they find the correct tuple version.

In addition, this patch introduces the ability to "prune" dead tuples on a
per-page basis, without having to do a complete VACUUM pass to recover space.
VACUUM is still needed to clean up dead index entries, however.

Pavan Deolasee, with help from a bunch of other people.
This commit is contained in:
Tom Lane
2007-09-20 17:56:33 +00:00
parent bbf4fdc253
commit 282d2a03dd
65 changed files with 3517 additions and 514 deletions
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6
src/backend/access/index/genam.c
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@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/index/genam.c,v 1.62 2007/05/27 03:50:38 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/index/genam.c,v 1.63 2007/09/20 17:56:30 tgl Exp $
*
* NOTES
* many of the old access method routines have been turned into
@@ -21,6 +21,7 @@
#include "access/genam.h"
#include "access/heapam.h"
#include "access/transam.h"
#include "miscadmin.h"
#include "pgstat.h"
@@ -95,6 +96,9 @@ RelationGetIndexScan(Relation indexRelation,
ItemPointerSetInvalid(&scan->xs_ctup.t_self);
scan->xs_ctup.t_data = NULL;
scan->xs_cbuf = InvalidBuffer;
scan->xs_prev_xmax = InvalidTransactionId;
scan->xs_next_hot = InvalidOffsetNumber;
scan->xs_hot_dead = false;
/*
* Let the AM fill in the key and any opaque data it wants.