Re: Is Hash Agg being used? 7.4 seems to handle this query worse than 7.3

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Greg Stark <gsstark(at)mit(dot)edu>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Is Hash Agg being used? 7.4 seems to handle this query worse than 7.3
Date: 2003-02-11 16:53:24
Message-ID: 26281.1044982404@sss.pgh.pa.us
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Greg Stark <gsstark(at)mit(dot)edu> writes:
> The query actually runs slightly slower in CVS than with 7.3, though
> it's hard to compare because it seems to have done everything
> differently. Every hash join has become a merge join and every merge
> join has become a hash join :/

The estimated row counts for the bottom-level scans show some
differences, which probably account for the differing choice of plans.

Are these actually the same data with up-to-date ANALYZE stats in both
cases? I do not recall that we've made any adjustments to the basic
statistical estimation routines since 7.3 ...

regards, tom lane

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