I'm doing some tests on fTools/Processing spatial operators, with a cover multilinestring layer and a base polygon layer.
Running the following query on PostGIS I get similar timings with st_intersection and st_difference: select l.osm_id,ST_intersection(l.geom,e.geom) as geom from linee_selezione as l,edifici_buffer as e where ST_Intersects(l.geom, e.geom) while if I run the Difference tool QGIS chokes and it takes magnitudes of more time then Clip. If made both tools as similar as possible, just changing this [1] line of code, but the difference in execution time remains big. I can't find out where is the difference, because both PostGIS and QGIS base the operations on GEOS. Any hints? giovanni [1] https://github.com/qgis/QGIS/blob/master/python/plugins/processing/algs/qgis/ftools/Clip.py#L107 -- Giovanni Allegri http://about.me/giovanniallegri Twitter: https://twitter.com/_giohappy_ blog: http://blog.spaziogis.it GEO+ geomatica in Italia http://bit.ly/GEOplus
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