From: Joe Conway <mail@joeconway.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Richard Jones <rich@annexia.org>
Cc: pgsql-sql@postgresql.org
Subject: Re: Very large IN-clause is slow, but how to rewrite it?
Date: Sun, 25 Feb 2007 10:27:08 -0800
Message-ID: <45E1D4FC.4050901@joeconway.com> (raw)
In-Reply-To: <7794.1172422591@sss.pgh.pa.us>
References: <20070225123913.GA17124@furbychan.cocan.org>
<7794.1172422591@sss.pgh.pa.us>
Tom Lane wrote:
> Richard Jones <rich@annexia.org> writes:
>> I've been profiling a PG database / mix of applications and found that
>> one statement which takes a very long time to execute is:
>
> PG 8.2 does better with long IN-lists ... although if the list is so
> long as to be fetching a significant fraction of the table, you'll still
> have problems. In that case I'd advise putting the values into a temp
> table, ANALYZEing same, and doing "WHERE foo IN (SELECT x FROM tmp_table)".
If 8.2, what about
... WHERE foo IN (select x from (values (1$),(2$),...,(N$)) as t(x))
?
It would be interesting to see how that compares performance-wise.
Joe
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To: pgsql-sql@postgresql.org
Cc: mail@joeconway.com, tgl@sss.pgh.pa.us, rich@annexia.org
Subject: Re: Very large IN-clause is slow, but how to rewrite it?
In-Reply-To: <45E1D4FC.4050901@joeconway.com>
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