From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | Greg Stark <gsstark(at)mit(dot)edu> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: 7.4 compatibility question |
Date: | 2003-10-24 04:09:17 |
Message-ID: | 200310240409.h9O49HE04743@candle.pha.pa.us |
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Lists: | pgsql-docs pgsql-hackers |
Greg Stark wrote:
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> 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
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
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