From: Jim Nasby <jnasby@enova.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Merlin Moncure <mmoncure@gmail.com>
Cc: pgsql-performance@postgresql.org <pgsql-performance@postgresql.org>
Subject: Re: Problems with hash join over nested loop
Date: Tue, 29 Oct 2013 11:52:32 -0500
Message-ID: <526FE7D0.9000605@enova.com> (raw)
In-Reply-To: <3692.1383065114@sss.pgh.pa.us>
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On 10/29/13 11:45 AM, Tom Lane wrote:
> Jim Nasby <jnasby@enova.com> writes:
>> I'm also wondering if it's time to raise those limits.
>
> Yeah, possibly. The current default values were set on machines much
> smaller/slower than most current hardware.
>
> I think also that the collapse limits were invented mainly to keep people
> out of GEQO's clutches, but we've made some significant fixes in GEQO
> since then. Maybe the real answer is to make the default collapse limits
> much higher, and lower geqo_threshold to whatever we think the threshold
> of pain is for applying the regular planner.
In my test case geqo does seem to do a good job. I'll see if I can get some data on how number of relations affects planning time... I don't get much of a warm fuzzy about lowering geqo...
--
Jim Nasby, Lead Data Architect (512) 569-9461
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To: pgsql-performance@postgresql.org
Cc: jnasby@enova.com, tgl@sss.pgh.pa.us, mmoncure@gmail.com
Subject: Re: Problems with hash join over nested loop
In-Reply-To: <526FE7D0.9000605@enova.com>
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