[postgis-users] Decomposing Multiploygon
ralph.mason at telogis.com
Tue Dec 16 18:49:26 PST 2003
Thanks for the answer, that did what I need however the performance is
To find the couniries takes 20 ms
SELECT gmi_cntry from countries where
the_geom ~= GeometryFromText('POINT(-105.0 52.0)',-1)
SELECT gmi_cntry from Countries where
the_geom ~= GeometryFromText('POINT(-105.0 52.0)',-1) and
contains(the_geom ,GeometryFromText('POINT(-105.0 52.0)',-1))
Takes 450 ms which seems like a huge difference.
Is there any way to improve this performance?
>See the Intersects(geometry, geometry) function.
>You need GEOS support compiled in.
>>I am new to postgis and spatial data so I apologies in advance if this
>>is covered already. Google didn't turn up anything.
>>I have a shape file of country outlines, each country is a multipolygon.
>>I imported this using shp2postgis and created an index on the geometry
>>column. So far so good.
>>However, as the a search is done on the bounding box of the multi
>>polygon I get more than one country returned to many searches. Eg
>>querying in canada will return Canada, USA (because of the alaska ,
>>mainland box), and Russia.
>>So - Is there a way to query for records that contain the point in one
>>of the polygons in the multipolygon? Or do I need to decompose the
>>multipolygon to a polygons?
>>Assuming I need to decompose, is there a utility that can do this (I
>>guess one could write a postgres function to do it)
>>Thanks for any help
>>postgis-users mailing list
>>postgis-users at postgis.refractions.net
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