Re: 7.3 vs 7.2 - different query plan, bad performance

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Ryszard Lach <siaco(at)autograf(dot)pl>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: 7.3 vs 7.2 - different query plan, bad performance
Date: 2003-06-16 14:17:43
Message-ID: 2680.1055773063@sss.pgh.pa.us
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Ryszard Lach <siaco(at)autograf(dot)pl> writes:
> The point is, that my tables (and queries) are a 'little' bit more
> complicated and I wanted to give as simple example as I could. I think
> that problem is that subselects are _much_slower_ executed in 7.3 than
> in 7.2, just as someone already wrote here.

No, the problem is that 7.3 fails to notice that it doesn't really need
to execute the subselect at all. This is the price we paid for being
sure that a post-release bug fix wouldn't break anything more serious.
There is a better fix in place for 7.4.

regards, tom lane

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