[postgis-users] ST_Overlaps and performance

[Stephen Woodbridge]

Try using st_dwith(cat.location, other_geom, 0.0)
This will include polygons that touch in addition to overlaps so you 
might want to add "and st_overlaps(...)" to the above condition.

-Steve W

On 3/7/2012 12:26 PM, DrYSG wrote:
> I have a table with 21 Million Rows. The Geometry field is a simple
> rectangular bounding box (Polygon with 4 corners).
>
> Users will be doing executing queries to find all overlapping rows to a user
> supplied rectangle. I have been finding that my naive query of:
>
> SELECT *
> FROM portal.metadata as cat
> WHERE ST_Overlaps(cat.location,ST_GeomFromText('POLYGON((-70.9433962
> 41.5384615,-72.5283019 41.5384615,-72.5283019 41.1538462,-70.9433962
> 41.1538462,-70.9433962 41.5384615))', 4326));
>
> Can take up to 40 seconds on a cold location. However, an ST_Contains query
> of a point is only about 8 seconds. Yes, location is indexed using GIST.
>
> CREATE INDEX catalog_location_idx
>    ON portal.catalog
>    USING gist
>    (location );
>
> Now, it first stuck me as odd that it was taking more than 4 times the point
> query to discover overlap. Then I thought about it, and I can see cases
> where there ST_Overlaps cannot assume certain geometries.
>
> I am now considering doing a WHERE clause that checks for ST_Contains for
> both the Top-Left and Bottom-Right corners of the QueryRectangle since I
> know that all bboxes in the DB are rectangular.
>
> But I thought I would see what those with knowledge of the internals of the
> spatial functions have to say.
>
> Ideas?
>
>
>
> --
> View this message in context: http://postgis.17.n6.nabble.com/ST-Overlaps-and-performance-tp4555465p4555465.html
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