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Allow HOT updates for some expression indexes

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If the value of an index expression is unchanged after UPDATE,
allow HOT updates where previously we disallowed them, giving
a significant performance boost in those cases.

Particularly useful for indexes such as JSON->>field where the
JSON value changes but the indexed value does not.

Submitted as "surjective indexes" patch, now enabled by use
of new "recheck_on_update" parameter.

Author: Konstantin Knizhnik
Reviewer: Simon Riggs, with much wordsmithing and some cleanup
This commit is contained in:
Simon Riggs
2018-03-27 19:57:02 +01:00
parent 1944cdc982
commit c203d6cf81
13 changed files with 395 additions and 22 deletions
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3
src/backend/catalog/index.c
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@@ -26,6 +26,7 @@
#include "access/amapi.h"
#include "access/multixact.h"
#include "access/relscan.h"
#include "access/reloptions.h"
#include "access/sysattr.h"
#include "access/transam.h"
#include "access/visibilitymap.h"
@@ -3863,7 +3864,7 @@ reindex_relation(Oid relid, int flags, int options)
/* Ensure rd_indexattr is valid; see comments for RelationSetIndexList */
if (is_pg_class)
(void) RelationGetIndexAttrBitmap(rel, INDEX_ATTR_BITMAP_ALL);
(void) RelationGetIndexAttrBitmap(rel, INDEX_ATTR_BITMAP_HOT);
PG_TRY();
{