Re: self join revisited

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Rikard Pavelic <rikard(dot)pavelic(at)zg(dot)htnet(dot)hr>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: self join revisited
Date: 2009-04-01 17:19:10
Message-ID: 7884.1238606350@sss.pgh.pa.us
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Rikard Pavelic <rikard(dot)pavelic(at)zg(dot)htnet(dot)hr> writes:
> It would be great if Postgres could rewrite this query

AFAICS those queries are not going to produce the same results,
so Postgres would be 100% incorrect to rewrite it like that for you.

(If they do produce the same results, it would depend on a bunch
of assumptions you have not stated.)

regards, tom lane

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