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From: Richard Huxton <dev@archonet.com>
To: Frank Jördens <frank@woome.com>
Cc: pgsql-sql@postgresql.org, Nic Ferrier <nferrier@woome.com>
Cc: Edward George <ed@woome.com>
Cc: Seb Potter <seb@woome.com>
Cc: Hannu Krosing <hannu@2ndquadrant.com>
Subject: Re: Make the planner smarter about idiosyncratic (or broken) ORM 	behaviour
Date: Fri, 22 May 2009 10:56:49 +0100
Message-ID: <4A1676E1.6010102@archonet.com> (raw)
In-Reply-To: <7d10d2df0905220233v3e54ab34lb9c3530fe3543a5c@mail.gmail.com>
References: <7d10d2df0905220233v3e54ab34lb9c3530fe3543a5c@mail.gmail.com>

Frank Jördens wrote:
> Our Django experts are telling me that it is probably not practical to
> fix in the ORM, as it seems to be structural (anyway not fixable for
> us in the near term). Hence I am wondering if anyone has an idea as to
> how to make the planner smarter about such weirdness (or brokenness);
> you might argue that the 2nd join there is merely syntactic bloat
> which the planner might just recognize as such?

Even if you have funding to hire a developer to adapt PG's planner, it's 
going to be an uphill struggle to get patches accepted unless there is a 
simple, quick can-merge-two-joins test someone can come up with. Time 
spent planning to deal with badly written queries costs every 
well-written query too of course.

Even with a patch and acceptance from core, 8.4 is in beta at the moment 
so you'll have a long wait before 8.5 comes out with your patch.

Are you sure it wouldn't be easier to hire a Python guru for a couple of 
days and have him/her hack the ORM to make it less, um, "simplistic"? 
There must be an "assemble references into JOINs" point in the code you 
could rationalise this at.

-- 
   Richard Huxton
   Archonet Ltd



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