Re: join removal

From: Marko Tiikkaja <marko(dot)tiikkaja(at)cs(dot)helsinki(dot)fi>
To: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Greg Stark <stark(at)mit(dot)edu>, "<pgsql-hackers(at)postgresql(dot)org>" <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: join removal
Date: 2010-03-29 08:25:31
Message-ID: 4BB063FB.90901@cs.helsinki.fi
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On 2010-03-29 11:19 +0200, Pavel Stehule wrote:
> postgres=# explain select a from a left join b on true;

This is effectively a cross join and it would give wrong answers. Try
SELECT a FROM a LEFT JOIN b ON a.a = b.b;

Regards,
Marko Tiikkaja

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