| From: | Martijn van Oosterhout <kleptog(at)svana(dot)org> |
|---|---|
| To: | JEAN-PIERRE PELLETIER <pelletier_32(at)sympatico(dot)ca> |
| Cc: | jim(at)nasby(dot)net, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Index ignored with "is not distinct from", 8.2 beta2 |
| Date: | 2006-11-07 10:03:42 |
| Message-ID: | 20061107100342.GA19789@svana.org |
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| Lists: | pgsql-hackers |
On Mon, Nov 06, 2006 at 09:10:40PM -0500, JEAN-PIERRE PELLETIER wrote:
> I understand that the planner doesn't use indexes for IS NOT DISTINCT FROM,
> but it would
> be good because "is not distinct from" is very useful when you have nulls
> but don't want to use three value logic.
The main issue is that currently indexes cannot be used to find NULLs
in a table. Patches have been created that cover most index types, but
it's not part of the main distribution.
Partial indexes can be a solution to the "x IS NULL" clauses.
Hope this helps,
--
Martijn van Oosterhout <kleptog(at)svana(dot)org> http://svana.org/kleptog/
> From each according to his ability. To each according to his ability to litigate.
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