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

[Greg Williamson]

You might provide a description of the tables (\d xxxx at the psql prompt), and perhaps the output of an "EXPLAIN ANALYZE" for this command. Any non-standard config settings might be of relevance as well.

Greg Williamson



----- Original Message -----
> From: Stefan Keller <sfkeller at gmail.com>
> To: PostGIS Users Discussion <postgis-users at postgis.refractions.net>
> Cc: 
> Sent: Thursday, February 16, 2012 3:51 PM
> Subject: [postgis-users] ST_Crosses doesn't use index?
> 
> 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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