From: PFC <lists@peufeu.com>
To: Richard Huxton <dev@archonet.com>
To: Luke Lonergan <LLonergan@greenplum.com>
Cc: albert@sedifa.com
Cc: pgsql-performance@postgresql.org
Subject: Re: Posible planner improvement?
Date: Wed, 21 May 2008 18:18:27 +0200
Message-ID: <op.ubih81yvcigqcu@apollo13.peufeu.com> (raw)
In-Reply-To: <48341F1D.3090304@archonet.com>
References: <014F2941B0A1EA47BD61D21526B806E90162C3D2@MI8NYCMAIL08.Mi8.com>
<48341F1D.3090304@archonet.com>
On Wed, 21 May 2008 15:09:49 +0200, Richard Huxton <dev@archonet.com>
wrote:
> Luke Lonergan wrote:
>> The problem is that the implied join predicate is not being
>> propagated. This is definitely a planner deficiency.
>
> IIRC only equality conditions are propagated and gt, lt, between aren't.
> I seem to remember that the argument given was that the cost of
> checking for the ability to propagate was too high for the frequency
> when it ocurred.
>
> Of course, what was true for code and machines of 5 years ago might not
> be so today.
>
Suggestion : when executing a one-off sql statement, optimizer should try
to offer "best effort while being fast" ; when making a plan that will be
reused many times (ie PREPARE, functions...) planning time could be
muuuuch longer...
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To: pgsql-performance@postgresql.org
Cc: lists@peufeu.com, dev@archonet.com, LLonergan@greenplum.com, albert@sedifa.com
Subject: Re: Posible planner improvement?
In-Reply-To: <op.ubih81yvcigqcu@apollo13.peufeu.com>
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