From 68ea2b7f9b52d35b5fcd9c8d44d88de5a64be3ba Mon Sep 17 00:00:00 2001
From: Simon Riggs
Date: Wed, 5 Apr 2017 18:22:32 -0400
Subject: Reduce lock level for CREATE STATISTICS

In line with other lock reductions related to planning.

Simon Riggs
---
 src/backend/commands/statscmds.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

(limited to 'src')

diff --git a/src/backend/commands/statscmds.c b/src/backend/commands/statscmds.c
index 8d483dbb3a7..46abadcc811 100644
--- a/src/backend/commands/statscmds.c
+++ b/src/backend/commands/statscmds.c
@@ -96,7 +96,13 @@ CreateStatistics(CreateStatsStmt *stmt)
 				 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);
 
 	if (rel->rd_rel->relkind != RELKIND_RELATION &&
-- 
cgit v1.2.3