| From: | Martijn van Oosterhout <kleptog(at)svana(dot)org> |
|---|---|
| To: | Postgres User <postgres(dot)developer(at)gmail(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-general <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: Regex query not using index |
| Date: | 2008-02-20 09:02:09 |
| Message-ID: | 20080220090209.GA32127@svana.org |
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| Thread: | |
| Lists: | pgsql-general |
On Wed, Feb 20, 2008 at 12:56:54AM -0800, Postgres User wrote:
> a final question: why does this syntax do a seq scan + filter:
>
> select * from tablea where fielda = fielda -or- select * from
> tablea where fielda in (fielda)
>
> while this syntax results in no filter, seq scan only
>
> select * from tablea where 1 = 1
>
> it seems that both where clauses should be ignored by the optimizer-
> or am i missing something
WHERE fielda = fielda will only match non-null rows...
Have a nice day,
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> Those who make peaceful revolution impossible will make violent revolution inevitable.
> -- John F Kennedy
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