[postgis-users] General PostGIS & GEOS comments and questions

Vinko Vrsalovic vinko at cprsig.cl
Thu Sep 4 02:34:58 PDT 2003


	After a few couple of hours with playing with the new postgis,
	here are some comments.

	I guess you are aware of this, but just in case, with the latest
	cvs code, when passing a wrong parameter (typically geometry
	collections, I guess this is the reason for the warning in the docs :)) 
	to a GEOS powered function, postgres (7.3.4) crashes.

	boundary(), when passed a geometry collection, throws an error 
	but it doesn't crash the server.

	Will there ever be support for geometry collections on GEOS
	powered functions, at least for some of them? Is this possible
	at all in all (or any) cases?

	And a related issue, is there/will there be a function to obtain 
	an envelope of the actual geometries, not their bounding boxes?

	In fact, what I'm looking for is to be able to do a
	contains(geom,collect(other_geom)), where geom is a POLYGON
	column, and other_geom is a column of GEOMETRY type, which 
	has different types of geometries. So far, the closest I've 
	arrived is to obtain the envelope()'s of the collect()'s, and
	then contains(geom,envelope).

	The goal, of course, is doing this in pure PostGIS, not pulling
	the data out to some program and then back. Stored procedures
	might be a good compromise. Any suggestions?

	I liked a lot how this is turning out to be, if before you could
	do a lot of great things with PostGIS, I can't even imagine the
	whole spectrum of possibilities now! 

Vinko Vrsalovic <el[|- at -|]vinko.cl>

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