Hi All I'm having an issue with ST_Union on a large dataset. I have a LINESTRING layer which I want to union. The layer has been validated using ST_IsValid with no invalid geometries found. The LINESTRING layer is formed from a large MULTIPOLYGON layer which is also validated. The St_Union function works alright when operating on subsets of the data but throws a nondescript error (ERROR: GEOS union() threw an error!) when run on the whole dataset. Are there known issues with ST_Union running on large datasets (~17000 geometries)? The SQL is below. I'm suspecting a memory issue but can't be sure. The same error has also occurred on our 64-bit Linux machine.
I've tried a number of work-arounds with no success. Firstly I tried breaking the process up so only spatially intersecting geometries were unioned and, secondly I've tweaked the processing memory variables for postgres. My current settings are below. --works fine CREATE TEMP TABLE all_lines AS SELECT gid, st_boundary(geom) as geom FROM (SELECT gid, (st_dump(geom)).geom as geom FROM featuresubset01) as foo GROUP BY gid, geom; --throws and error when run on whole dataset CREATE TEMP TABLE noded_lines AS SELECT St_Union(geom) AS geom FROM all_lines; Postgres Memory Settings: shared_buffers = 150MB temp_buffers = 25MB work_mem = 5MB maintenance_work_mem = 16MB Cheers Adrian Environ Specs: Postgres 8.4.8 PostGIS 1.5.3 Windows XP 32-bit SP3 3.25GB RAM Notice: This email and any attachments may contain information that is personal, confidential, legally privileged and/or copyright.No part of it should be reproduced, adapted or communicated without the prior written consent of the copyright owner. It is the responsibility of the recipient to check for and remove viruses. If you have received this email in error, please notify the sender by return email, delete it from your system and destroy any copies. You are not authorised to use, communicate or rely on the information contained in this email. Please consider the environment before printing this email.
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