Horton

Re: Re: new patch of MERGE (merge_204) & a question about duplicated ctid

Florian G. Pflug <fgp@phlo.org>

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From: Florian Pflug <fgp@phlo.org>
To: Robert Haas <robertmhaas@gmail.com>
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: 2011-01-03T16:36:25Z
Lists: pgsql-hackers 
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...

best regards,
Florian Pflug