Re: Re: new patch of MERGE (merge_204) & a question about duplicated ctid
Robert Haas <robertmhaas@gmail.com>
From: Robert Haas <robertmhaas@gmail.com>
To: Florian Pflug <fgp@phlo.org>
Cc: Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>, Stephen Frost <sfrost@snowman.net>, Simon Riggs <simon@2ndquadrant.com>, Greg Smith <greg@2ndquadrant.com>, Marko Tiikkaja <marko.tiikkaja@cs.helsinki.fi>, Boxuan Zhai <bxzhai2010@gmail.com>, pgsql-hackers@postgresql.org
Date: 2011-01-03T17:09:32Z
Lists: pgsql-hackers
On Mon, Jan 3, 2011 at 11:36 AM, Florian Pflug <fgp@phlo.org> wrote: > On Jan3, 2011, at 17:21 , Robert Haas wrote: >> On Mon, Jan 3, 2011 at 11:08 AM, Heikki Linnakangas >>> In serializable mode you get a serialization error. >> >> I don't think this part is true. You can certainly do this: >> >> CREATE TABLE test (a int); >> BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE; >> SELECT * FROM test; >> <in another session, insert (1) into test> >> LOCK TABLE test IN SHARE MODE; -- or just LOCK TABLE test, if you prefer >> SELECT * FROM test; -- still ain't there >> INSERT INTO test VALUES (1); > > In SERIALIZABLE mode, you need to take any table-level locks before obtaining > a snapshot. There's even a warning about this in the docs somewhere IIRC... That should be safe, if people do it that way. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company