[postgis-users] question on gist performance

[Frank Koormann]

Stefan,

* Stefan Zweig <stefanzweig1881 at web.de> [070907 10:07]:
> thanks for your quick reply. i have tried your advice and rebuilded
> all my gist indexes on the table (via drop index, create index) and
> run a vacuum full afterwards. but that did not change the fact, that
> the query on the_geom is much slower than the same one on the_geom_1.
> 
[...]
> 
>   '...WHERE the_geom && expr;' takes about 250ms,
>   '...WHERE the_geom_envelope && expr;' takes about 20ms.
> 
> ANALYZE says that GIST is used. As far as I know, the GIST makes use
> only of the bounding boxes of Geometry objects, which are equal for
> each object. How does it come that the query time using the_geom is more than
> *ten times slower* than the query time using the_geom_envelope?"

It would help if you post the explain analyse output.

Regards,

        Frank

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