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Re: No hash join across partitioned tables?

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Kris Jurka <books(at)ejurka(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: No hash join across partitioned tables?
Date: 2010-07-02 03:00:00
Message-ID: 201007020300.o62300V21807@momjian.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-performance
Tom Lane wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> > In going back through emails I had marked as possibly needing another
> > look before 9.0 is released, I came across this issue again.  As I
> > understand it, analyze (or analyse) now collects statistics for both
> > the parent individually, and for the parent and its children together.
> >  However, as I further understand it, autovacuum won't actually fire
> > off an analyze unless there's enough activity on the parent table
> > considered individually to warrant it.  So if you have an empty parent
> > and a bunch of children with data in it, your stats will still stink,
> > unless you analyze by hand.
> 
> Check.
> 
> > Assuming my understanding of the problem is correct, we could:
> 
> > (a) fix it,
> > (b) document that you should consider periodic manual analyze commands
> > in this situation, or
> > (c) do nothing.
> 
> > Thoughts?
> 
> The objections to (a) are that it might result in excessive ANALYZE work
> if not done intelligently, and that we haven't got a patch ready anyway.
> I would have liked to get to this for 9.0 but I feel it's a bit late
> now.

What do we want to do about the above issue?

-- 
  Bruce Momjian  <bruce(at)momjian(dot)us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + None of us is going to be here forever. +

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