From: Tom Lane <tgl@sss.pgh.pa.us>
To: Mike Winter <mike.winter@*nospam**frontlogic.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: Question about slow Select when using 'IN'.
Date: Tue, 03 Dec 2002 02:06:16 -0500
Message-ID: <20934.1038899176@sss.pgh.pa.us> (raw)
In-Reply-To: <Pine.LNX.4.33L2.0211291623260.18672-100000@frontlogic.com>
References: <Pine.LNX.4.33L2.0211291623260.18672-100000@frontlogic.com>
Mike Winter <mike.winter@*nospam**frontlogic.com> writes:
> My query is of the form:
> SELECT col, count(col) FROM tab WHERE id IN (3,
> 4,7,2, ...) GROUP BY COL ORDER BY count
> for a very large number of rows.
> I have an index on id, so the explain looks like:
> Aggregate (cost=12.12..12.14 rows=1 width=5)
> -> Group (cost=12.12..12.13 rows=4 width=5)
> -> Sort (cost=12.12..12.12 rows=4 width=5)
> -> Index Scan using col_id_idx2, col_id_idx2, col_id_idx2,
> col_id_idx2 on tab (cost=0.00..12.08 rows=4 width=5)
The planner obviously does not think this is a large table (the cost
estimates correspond to very small numbers of pages). I wonder
whether you have ever VACUUMed or ANALYZEd the table.
regards, tom lane
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To: pgsql-sql@postgresql.org
Cc: tgl@sss.pgh.pa.us, mike.winter@*nospam**frontlogic.com
Subject: Re: Question about slow Select when using 'IN'.
In-Reply-To: <20934.1038899176@sss.pgh.pa.us>
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