On Tue, Sep 7, 2010 at 1:21 PM, Sean <[email protected]> wrote: > > > On Sep 3, 12:55 pm, John Poole <[email protected]> wrote: >> I have a table of assessor parcels (polygons) and I want to take a >> given point (actually will be taking samplings from a geocache >> tracker, so I'll be doing hundreds, possibly thousands of such >> queries) and determine which, if any, of the shapes contain the point. >> The goal is to determine which parcel a tracked person is within and >> at what times. >> >> I'm new to spatial database, and suspect performing a relate or >> ST_contains against the 40,000 shapes would be horribly inefficient, >> especially if I have thousands of points. Should I be reading up on >> indexes, or is there an elegant solution to this problem. >> >> I tried searching the archive of this list for "point in field of >> shapes" but results were too generic. >> >> John L. Poole > > That shouldn't be very taxing. A bounding box check in the where > clause should help speed things up. e.g. > > select p.id > from parcels p left join geocache g on st_contains(p.geom, g.geom) > where p.geom && g.geom > > You'll only really know how efficient it is when you try it with real > data. Of course, make sure you have a spatial index on the polygons. > > Sean > _______________________________________________ > postgis-users mailing list > [email protected] > http://postgis.refractions.net/mailman/listinfo/postgis-users >
You're right, it was not taxing, my worry was misplaced and the response times are within acceptable ranges. Thank you -- John L. Poole P.O. Box 6566 Napa, CA 94581-6566 707-812-1323 [email protected] _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
