Re: 8.4/9.0 simple query performance regression

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Josh Berkus <josh(at)agliodbs(dot)com>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: 8.4/9.0 simple query performance regression
Date: 2011-06-06 23:02:23
Message-ID: 14955.1307401343@sss.pgh.pa.us
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Josh Berkus <josh(at)agliodbs(dot)com> writes:
> Just got this simple case off IRC today:
> [ hashed versus non-hashed subplan ]
> I'm at a bit of a loss as to what's happening here.

Possibly work_mem is smaller in the second installation?

(If I'm counting on my fingers right, you'd need a setting of at least a
couple MB to let it choose a hashed subplan for this case.)

regards, tom lane

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