What you probably mean is that a query like Select geom from mytable where ST_Intersects(geom,my_rectangular_selection) is very efficient, right?Do I have to be careful to create indexes, or is that done automatically when I add a geometrical column?
--- On Tue, 11/24/09, Brian Modra <[email protected]> wrote: From: Brian Modra <[email protected]> Subject: Re: [postgis-users] Using a rectangular selection To: "PostGIS Users Discussion" <[email protected]> Date: Tuesday, November 24, 2009, 5:00 AM 2009/11/23 Henri De Feraudy <[email protected]> > > Hi, > I'm working in planar coordinates. I have a Postgis database and > for starters I want to limit my attention to all geometries that intersect a > given rectangle (the "selection"). > I can imagine that one could enumerate all geometries and ask in each case if > they > intersect the rectangle, but that doesnt seem very efficient, so what do you > suggest? Use ST_Intersects > I only need general guidance so I can look at the various parts of the doc. > Later I'll be wanting to clip the geometies with this selection. > Still later I'll want to consider polygonal selections. > By the way I'm accessing the PostGis database via LibPQ and have written my > application > in Qt. > > Thanking you in advance > Henri > > _______________________________________________ > postgis-users mailing list > [email protected] > http://postgis.refractions.net/mailman/listinfo/postgis-users > -- Brian Modra Land line: +27 23 5411 462 Mobile: +27 79 69 77 082 5 Jan Louw Str, Prince Albert, 6930 Postal: P.O. Box 2, Prince Albert 6930 South Africa http://www.zwartberg.com/ _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
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