Re: MIN() performance regression 8.0 -> 8.1

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Paul Lindner <lindner(at)inuus(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: MIN() performance regression 8.0 -> 8.1
Date: 2005-12-05 03:05:35
Message-ID: 12394.1133751935@sss.pgh.pa.us
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Paul Lindner <lindner(at)inuus(dot)com> writes:
> I believe I've found a performance regression between 8.0 and 8.1 for
> some cases. For some queries it appears that the old MIN() ran much
> faster than the new optimized MIN().

When you are complaining about planner mistakes, showing EXPLAIN rather
than EXPLAIN ANALYZE output is an entirely ineffective way of making
your point.

I suspect the problem is that there is a correlation between the
moo_summary_date and moo_summary_b_id columns, which the planner
will not realize --- is that the case?

regards, tom lane

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