[postgis-users] Union fails on 2389 linestrings.

Jeff Adams jadams at azavea.com
Tue Jul 27 07:03:07 PDT 2010

I have a layer with 2389 linestrings which intersect a lot.  I'm
trying to create a polygon overlay, so I want to union the linestrings
together so I can then call polygonize.

However, when I try to union them, it runs for about 25 minutes then
fails claiming it found a non-noded intersection between two lines
that appear identical and 0-length (though it may be the precision is
lost when printing the WKT in the error message).

	create table noded_lines as
	select ST_Union(boundary) as noded_boundary from boundary_lines;

NOTICE:  TopologyException: found non-noded intersection between
LINESTRING (-118.296 34.1185, -118.296 34.1185) and LINESTRING
(-118.296 34.1185, -118.296 34.1185) at -118.296 34.1185

ERROR:  GEOS union() threw an error!

Anyone know how I could get around this?


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