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Reduce lock level for CREATE STATISTICS

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In line with other lock reductions related to planning.

Simon Riggs
This commit is contained in:
Simon Riggs 2017-04-05 18:22:32 -04:00
parent 2686ee1b7c
commit 68ea2b7f9b
2 changed files with 9 additions and 2 deletions
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3
doc/src/sgml/mvcc.sgml
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@ -923,7 +923,8 @@ ERROR: could not serialize access due to read/write dependencies among transact
<para> <para>
Acquired by <command>VACUUM</command> (without <option>FULL</option>), Acquired by <command>VACUUM</command> (without <option>FULL</option>),
<command>ANALYZE</>, <command>CREATE INDEX CONCURRENTLY</>, and <command>ANALYZE</>, <command>CREATE INDEX CONCURRENTLY</>,
<command>CREATE STATISTICS</> and
<command>ALTER TABLE VALIDATE</command> and other <command>ALTER TABLE VALIDATE</command> and other
<command>ALTER TABLE</command> variants (for full details see <command>ALTER TABLE</command> variants (for full details see
<xref linkend="SQL-ALTERTABLE">). <xref linkend="SQL-ALTERTABLE">).

8
src/backend/commands/statscmds.c
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@ -96,7 +96,13 @@ CreateStatistics(CreateStatsStmt *stmt)
errmsg("statistics \"%s\" already exist", namestr))); errmsg("statistics \"%s\" already exist", namestr)));
} }
rel = heap_openrv(stmt->relation, AccessExclusiveLock); /*
* CREATE STATISTICS will influence future execution plans but does
* not interfere with currently executing plans so it is safe to
* take only ShareUpdateExclusiveLock on relation, conflicting with
* ANALYZE and other DDL that sets statistical information.
*/
rel = heap_openrv(stmt->relation, ShareUpdateExclusiveLock);
relid = RelationGetRelid(rel); relid = RelationGetRelid(rel);
if (rel->rd_rel->relkind != RELKIND_RELATION && if (rel->rd_rel->relkind != RELKIND_RELATION &&