From: | "Dan Langille" <dan(at)langille(dot)org> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-sql <pgsql-sql(at)postgresql(dot)org> |
Subject: | Re: why the big difference on this explain analyze? |
Date: | 2002-03-16 22:22:55 |
Message-ID: | 20020316222258.15B653F28@bast.unixathome.org |
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Lists: | pgsql-sql |
On 16 Mar 2002 at 17:19, Tom Lane wrote:
> "Dan Langille" <dan(at)langille(dot)org> writes:
> > The difference between the two SQL statements is the inclusion of
> > Ports_Check in the WHERE EXISTS select clause.
>
> Which caused it to do the wrong thing. I think you'll find this
> command set found_in_ports = TRUE in *every* row of Ports_Check.
Yes, it did. Not quite what I want either....
> Reason: the EXISTS clause no longer depends on the outer update,
> but evaluates to a constant TRUE. (Or possibly a constant FALSE,
> but that seems unlikely.)
Seems I'll have to keep searching for my speed improvement. Thanks for
pointing out that problem. cheers.
--
Dan Langille
The FreeBSD Diary - http://freebsddiary.org/ - practical examples
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