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Re: Was partitioned table row estimation fixed in 9.0?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Josh Berkus <josh(at)agliodbs(dot)com>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Was partitioned table row estimation fixed in 9.0?
Date: 2010-02-27 03:00:09
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
Josh Berkus <josh(at)agliodbs(dot)com> writes:
> There were a flurry of patches around this from Stark and Aster Data, so
> I'm checking if I should be testing on 9.0 or adding this to the TODO list.

> The problem I'm grappling with is that OUTER JOINS against the master in
> a partitioned table (joining to the append node) gives a row estimate
> which does not take into account any CE applicable to the partitioned
> table.  The CE is properly executed when the join is actually executed,
> but with the row estimate way off (orders of magnitude) you often get
> bad plans for other joins in the query.

Would you give a concrete example?  There was some work done in this
area but it's impossible to tell whether it solves your problem with
only that much detail.

			regards, tom lane

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