Hello.

Why adding FK creates AccessExclusiveLock on referenced tabble?

{{{
CREATE TABLE A ( id integer, idb integer );
INSERT INTO A (id,idb) SELECT x, x%4 FROM generate_series(1,100) x;

CREATE TABLE B ( id int primary key );
INSERT INTO B VALUES (0),(1),(2),(3);

BEGIN;
ALTER TABLE A ADD CONSTRAINT a_idb_fkey FOREIGN KEY (idb) REFERENCES b;
SELECT * FROM pg_locks l, pg_class c WHERE l.pid = pg_backend_pid() AND 
l.locktype='relation' AND l.mode ilike '%exclusive%' AND l.relation=c.oid;
ROLLBACK;
}}}


Last SELECT is showing AccessExclusive on B.
Why not Exclusive?


Thanks,
Filip

Responses

• Fwd: question on foreign key lock at 2012-11-08 08:45:58 from Filip Rembiałkowski

pgsql-hackers by date

Next:	From: John Lumby	Date: 2012-11-01 16:37:14
	Subject: Re: [PATCH] Prefetch index pages for B-Tree index scans
Previous:	From: Kevin Grittner	Date: 2012-11-01 13:45:18
	Subject: Re: Estimation of HashJoin Cost

pgsql-general by date

Next:	From: Alban Hertroys	Date: 2012-11-01 16:40:23
	Subject: Re: Unexplained Major Vacuum Archive Activity During Vacuum
Previous:	From: Vincent Veyron	Date: 2012-11-01 16:24:22
	Subject: Re: role does not exist