[postgis-users] ST_Crosses doesn't use index?

[Paul Ramsey]

Stefan,

This has to do with your data / configuration, not ST_Crosses, as the
function clearly includes an index call.

CREATE OR REPLACE FUNCTION ST_Crosses(geometry,geometry)
        RETURNS boolean
        AS 'SELECT $1 && $2 AND _ST_Crosses($1,$2)'
        LANGUAGE 'SQL' IMMUTABLE;

P.

On Thu, Feb 16, 2012 at 3:51 PM, Stefan Keller <sfkeller at gmail.com> wrote:
> Hi
>
> ST_Crosses doc says that it uses the spatial index (if available).
> But I'm afraid it's not. I'm using PostGIS 1.5 on Linux.
>
> -- as it should be:
> SELECT name
> FROM osm_line a, osm_line b
> WHERE a.osm_id != b.osm_id
> AND ST_Crosses(a.way, b.way)
> -- takes longer than 60 sec, 586 features.
>
> -- now with ST_Contains:
> SELECT name
> FROM osm_line a, osm_line b
> WHERE ST_Contains('BOX(8.775 47.245, 8.873 47.208'::box2d,a.way)
> AND ST_Contains('BOX(8.775 47.245, 8.873 47.208'::box2d,b.way)
> AND a.osm_id != b.osm_id
> AND ST_Crosses(a.way, b.way)
> -- takes 3.5sec, 586 features.
>
> Obviously ST_Crosses does not consider the geometry index.
> Why this?
>
> Yours, Stefan
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