From: | Jayadevan M <maymala(dot)jayadevan(at)gmail(dot)com> |
---|---|
To: | "pgsql-general(at)postgresql(dot)org" <pgsql-general(at)postgresql(dot)org> |
Subject: | WITH and exclusive locks |
Date: | 2013-11-23 12:16:28 |
Message-ID: | CAFS1N4h1PfYZrEKbp-3FHXEZoE4NN6u2WskGRm50Vsf6ae0Y=Q@mail.gmail.com |
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Lists: | pgsql-general |
Hi,
When conducting performance tests of our application, I saw quite a few
exclusive locks in SELECTs with WITH clause. So I created a big table and
executed a query which takes time.
with x as (select * from emp where first_name like 'Sco%')
select * from x;
I got 2 locks - one accesshare lock against the table and one ExclusiveLock
with out any database/relation.
2417 postgres 10/95 10/95 ExclusiveLock Yes
2013-11-23 17:38:58+05:30
My guess is that the Exclusive lock is against some in-memory structure
(the temp table created by the WITH clause) and hence is not an issue. Is
that correct?
Regards,
Jayadevan
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