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From: Bruce Momjian <[email protected]>
To: Greg Stark <[email protected]>
Cc: [email protected]
Subject: Re: 7.4 compatibility question
Date: Fri, 24 Oct 2003 00:09:17 -0400 (EDT)
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

Greg Stark wrote:
> Bruce Momjian <[email protected]> writes:
> 
> > Michael Brusser wrote:
> >
> > > Optimizer improvements
> > >  => this tells me nothing. I suppose this could be a minor internal code
> > > tweak, which does not affect me. On the other hand this could be a major
> > > breakthrough, so now I can run some stupid query which would take
> > > a week to complete in the previous release. How do I know? 
> > 
> > Yes, this is always very hard to explain. The optimizer itself is
> > complex, and uses complex terms like merge join and key pruning.  It is
> > hard to explain what queries will be affected, though the basic issue is
> > that the optimizer will choose a better plan more frequently.
> 
> One thing that might be worth mentioning is that "WHERE foo IN (subquery)"
> type queries are much improved. That's a one of the more common complaints
> about 7.3 and previous and it's one that fairly easy to recognize.

That is right at the top of the release notes:

   Performance
          IN/NOT IN subqueries are now much more efficient

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  [email protected]               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

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