From: Jeff Larsen <jlar310@gmail.com>
To: pgsql-performance@postgresql.org
Subject: Re: Union within View vs.Union of Views
Date: Sat, 3 Nov 2007 20:57:21 -0500
Message-ID: <d1f9b6f00711031857s2972e92dgcedb209233f2485a@mail.gmail.com> (raw)
In-Reply-To: <3248.1194140315@sss.pgh.pa.us>
References: <d1f9b6f00711031322h1d2858d4xbfff4852941d405b@mail.gmail.com>
<472CFE4B.5060606@enterprisedb.com>
<3248.1194140315@sss.pgh.pa.us>
[[ Oops, still not used to gmail. Accidentally posted this straight to
Tom and not the list]]
> There are a bunch of special cases where it can't do that, though.
> Look into src/backend/optimizer/path/allpaths.c, particularly
> subquery_is_pushdown_safe:
My case probably fits the 'special case' description. Not all the
columns in each subquery matched up, so there were NULL::text
placeholders in some spots in the SELECT. In the case where
performance got bad, one of those columns was included in the
application's WHERE clause.
That's a good enough explanation for me. I'll spare you the gory
details of my tables, unless a developer wants to have a look at it
off-list.
Jeff
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To: pgsql-performance@postgresql.org
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Subject: Re: Union within View vs.Union of Views
In-Reply-To: <d1f9b6f00711031857s2972e92dgcedb209233f2485a@mail.gmail.com>
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