On Tue, Mar 03, 2020 at 10:12:05AM +0000, paul.m...@lfv.se wrote: > There was no difference between st_union() and st_unaryunion() when merging > all adjacent polygons to larger polygons. > The st_buffer() method is 3.5 times faster.
The reason why ST_Buffer is faster is because it builds the topology of the geometry only once, while ST_Union builds it for each pair of geometries taken in exam. The ST_UnaryUnion version simply chooses which pair of geometries to union in order for the operation to be as effective as possible (drop more edges). There was a reason why we decided NOT to use GEOS Buffer internally for UnaryUnion, probably had to do with robustness, but I forgot the details. Maybe Martin can help here ? --strk; _______________________________________________ postgis-users mailing list postgis-users@lists.osgeo.org https://lists.osgeo.org/mailman/listinfo/postgis-users
