From: Tom Lane <tgl@sss.pgh.pa.us>
To: Karim Nassar <Karim.Nassar@acm.org>
Cc: pgsql-performance@postgresql.org
Subject: Re: Delete query takes exorbitant amount of time
Date: Thu, 24 Mar 2005 19:52:07 -0500
Message-ID: <2630.1111711927@sss.pgh.pa.us> (raw)
In-Reply-To: <1111709457.9085.127.camel@k2.cet.nau.edu>
References: <1111709457.9085.127.camel@k2.cet.nau.edu>
Karim Nassar <Karim.Nassar@acm.org> writes:
> Here is the statement:
> orfs=# explain analyze DELETE FROM int_sensor_meas_type WHERE
> id_meas_type IN (SELECT * FROM meas_type_ids);
> QUERY PLAN
> -----------------------------------------------------------------------------------------------------------------------------
> Hash Join (cost=11.53..42.06 rows=200 width=6) (actual
> time=1.564..2.840 rows=552 loops=1)
> ...
> Total runtime: 2499616.216 ms
> (7 rows)
Notice that the actual join is taking 2.8 ms. The other ~40 minutes is
in operations that we cannot see in this plan, but we can surmise are ON
DELETE triggers.
> Where do I go from here?
Look at what your triggers are doing. My private bet is that you have
unindexed foreign keys referencing this table, and so each deletion
forces a seqscan of some other, evidently very large, table(s).
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, Karim.Nassar@acm.org
Subject: Re: Delete query takes exorbitant amount of time
In-Reply-To: <2630.1111711927@sss.pgh.pa.us>
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