From: Tom Lane <tgl@sss.pgh.pa.us>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Claus Stadler <cstadler@informatik.uni-leipzig.de>
Cc: pgsql-performance@postgresql.org
Subject: Re: ...WHERE TRUE" condition in union results in bad query pla
Date: Tue, 03 Apr 2012 11:35:34 -0400
Message-ID: <7810.1333467334@sss.pgh.pa.us> (raw)
In-Reply-To: <CA+TgmoY0rAmQ1W4WsixQajmFpKBAV4i9m4rnN3F2R=2qR+R2zw@mail.gmail.com>
References: <4F529E85.8010506@informatik.uni-leipzig.de>
<1857.1330830209@sss.pgh.pa.us>
<CA+TgmoY0rAmQ1W4WsixQajmFpKBAV4i9m4rnN3F2R=2qR+R2zw@mail.gmail.com>
Robert Haas <robertmhaas@gmail.com> writes:
> On Sat, Mar 3, 2012 at 10:03 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Sooner or later I'd like to relax the restriction that appendrel members
>> can't have extra WHERE clauses, but don't hold your breath waiting...
> Does this comment need updating?
> * Note: the data structure assumes that append-rel members are single
> * baserels. This is OK for inheritance, but it prevents us from pulling
> * up a UNION ALL member subquery if it contains a join. While that could
> * be fixed with a more complex data structure, at present there's not much
> * point because no improvement in the plan could result.
No, that's a different restriction.
regards, tom lane
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To: pgsql-performance@postgresql.org
Cc: tgl@sss.pgh.pa.us, robertmhaas@gmail.com, cstadler@informatik.uni-leipzig.de
Subject: Re: ...WHERE TRUE" condition in union results in bad query pla
In-Reply-To: <7810.1333467334@sss.pgh.pa.us>
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