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Re: Strange query plan

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Oleg Bartunov <oleg(at)sai(dot)msu(dot)su>
Cc: Pgsql Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Strange query plan
Date: 2001-06-05 14:42:34
Message-ID: (view raw or whole thread)
Lists: pgsql-hackers
Oleg Bartunov <oleg(at)sai(dot)msu(dot)su> writes:
> should be
> select msg_prt.tid as mid from msg_prt
>  where exists (select idx.tid from idx where msg_prt.tid=idx.tid
>                and idx.did=1 and ( idx.lid = 1207 or idx.lid=59587 ));
> but this is not a big win.

Shouldn't be any win at all: the IN expression-list notation will get
translated to exactly that form.

> Anyway, what's about original query ?

IN/EXISTS subqueries suck.  This has been true for a long time and is
going to be true for a while longer, unless someone else fixes it before
I have a chance to look at it.  See if you can't rewrite your query as
a plain join.

			regards, tom lane

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