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Re: Optimizer oddness, possibly compounded in 8.1

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Philip Warner <pjw(at)rhyme(dot)com(dot)au>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Optimizer oddness, possibly compounded in 8.1
Date: 2005-12-02 15:42:48
Message-ID: 2954.1133538168@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Philip Warner <pjw(at)rhyme(dot)com(dot)au> writes:
> The optimizer seems to want to use sequential scans on inherited tables
> when crossed with another table, as the following seems to demonstrate:

Is it intentional that your test case omits an analyze on t2?  Coz when
I add that, I get the same plan you show for 8.0.  Without the knowledge
that t2 is small, that plan is not a good choice.

(The larger point that joins of inheritance unions aren't well-planned
is true, but it's always been true...)

			regards, tom lane

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