Add note to ST_Equals that the function does not support geometry collections #14

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@nmandery
nmandery commented Dec 2, 2013

I just had a situation where ST_Equals failed to compare GeometryCollections. Looking add the source this is normal behavior, but there is no mention of it in the docs of ST_Equals.

This pull request adds a section to the documentation.

@robe2 robe2 was assigned by strk Sep 24, 2014
@strk
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strk commented Sep 24, 2014

@robe2 can you look at this ?

@mwtoews
mwtoews commented Apr 12, 2015

The problem is deeper than just ST_Equals. See http://lists.osgeo.org/pipermail/postgis-devel/2015-April/024827.html

If you have a homogeneous geometry collection, e.g. from ST_Polygonize, then use ST_CollectionExtract(geom, 3) to get a MultiPolygon, which works with ST_Equals and other relate functions.

@strk
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strk commented Nov 20, 2015

@nmandery are you planning to provide better wording for the manual about this ?
It's basically that geometrycollection with proper topology work while those with ambiguous one would not. A workaround is to pass them through ST_UnaryUnion beforehand.
See https://trac.osgeo.org/geos/ticket/725

@pramsey pramsey closed this Feb 25, 2016
@strk strk pushed a commit that referenced this pull request Feb 25, 2016
@pramsey pramsey Add note per #14
git-svn-id: http://svn.osgeo.org/postgis/trunk@14693 b70326c6-7e19-0410-871a-916f4a2858ee
befd771
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