Re: partitioning max() sql not using index

From: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
To: Kevin Kempter <kevink(at)consistentstate(dot)com>
Cc: PostgreSQL Performance <pgsql-performance(at)postgresql(dot)org>
Subject: Re: partitioning max() sql not using index
Date: 2009-09-09 10:05:22
Message-ID: 4AA77DE2.80005@enterprisedb.com
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Kevin Kempter wrote:
> Hi all I have a large table (>2billion rows) that's partitioned by date based
> on an epoch int value. We're running a select max(id) where id is the PK. I
> have a PK index on each of the partitions, no indexes at all on the base
> table.
>
> If I hit a partition table directly I get an index scan as expected:

The planner isn't smart enough to create the plan you're expecting.
There was discussion and even a patch posted recently about that:

http://archives.postgresql.org/pgsql-hackers/2009-07/msg01115.php

It seems the thread petered out, but the concept seems sane.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com

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