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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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2
src/include/access/reloptions.h
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@@ -51,6 +51,7 @@ typedef enum relopt_kind
RELOPT_KIND_PARTITIONED = (1 << 11),
/* if you add a new kind, make sure you update "last_default" too */
RELOPT_KIND_LAST_DEFAULT = RELOPT_KIND_PARTITIONED,
RELOPT_KIND_INDEX = RELOPT_KIND_BTREE|RELOPT_KIND_HASH|RELOPT_KIND_GIN|RELOPT_KIND_SPGIST,
/* some compilers treat enums as signed ints, so we can't use 1 << 31 */
RELOPT_KIND_MAX = (1 << 30)
} relopt_kind;
@@ -276,6 +277,7 @@ extern bytea *heap_reloptions(char relkind, Datum reloptions, bool validate);
extern bytea *view_reloptions(Datum reloptions, bool validate);
extern bytea *index_reloptions(amoptions_function amoptions, Datum reloptions,
bool validate);
extern bytea *index_generic_reloptions(Datum reloptions, bool validate);
extern bytea *attribute_reloptions(Datum reloptions, bool validate);
extern bytea *tablespace_reloptions(Datum reloptions, bool validate);
extern LOCKMODE AlterTableGetRelOptionsLockLevel(List *defList);