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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Jeff Janes <jeff.janes@gmail.com>
Cc: Pavel Stehule <pavel.stehule@gmail.com>
Cc: Felix Geisendörfer <felix@felixge.de>
Cc: pgsql-performa. <pgsql-performance@postgresql.org>
Subject: Re: Extremely slow HashAggregate in simple UNION query
Date: Sat, 24 Aug 2019 15:41:03 -0400
Message-ID: <6839.1566675663@sss.pgh.pa.us> (raw)
In-Reply-To: <CAMkU=1yiC23_F5OvQfh2qN2OMTx-95njbz2uskPB01dt2d_BNA@mail.gmail.com>
References: <9ADCDD19-555B-4DB0-B00C-1852AC361557@felixge.de>
	<CAMkU=1x+aT9kWCWKoskOdQPAdXZwLsv-cpKJ6B=rytCibfrpyA@mail.gmail.com>
	<CAFj8pRBsp+8FNEqVz9b76qMGn8P3-O5kFNiLkvu55Q+d+ntx5A@mail.gmail.com>
	<CAMkU=1yiC23_F5OvQfh2qN2OMTx-95njbz2uskPB01dt2d_BNA@mail.gmail.com>

Jeff Janes <jeff.janes@gmail.com> writes:
> Most of the time is not after the clock stops, but before the stepwise
> ANALYZE clock starts.  If you just do an EXPLAIN rather than EXPLAIN
> ANALYZE, that is also slow.  The giant hash table is created during the
> planning step (or somewhere around there

It's in executor startup, I believe.

			regards, tom lane





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