| From: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
|---|---|
| To: | Marko Tiikkaja <marko(dot)tiikkaja(at)cs(dot)helsinki(dot)fi> |
| 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 08:33:07 |
| Message-ID: | 162867791003290133i30f42b89ha084ab67ac6bf007@mail.gmail.com |
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| Lists: | pgsql-hackers |
2010/3/29 Marko Tiikkaja <marko(dot)tiikkaja(at)cs(dot)helsinki(dot)fi>:
> On 2010-03-29 11:19 +0200, Pavel Stehule wrote:
>> postgres=# explain select a from a left join b on true;
you have a true.
I forgot SELECT DISTINCT
regards
Pavel
>
> 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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