[postgis-devel] Is errorIfGeometryCollection necessary for relate ops?

[Mike Toews]

I'm wondering why expressions like this have an error:

SELECT ST_Equals(
  'GEOMETRYCOLLECTION(POINT(1 2),POINT(3 4))',
  'GEOMETRYCOLLECTION(POINT(3 4),POINT(1 2))');

ERROR:  Relate Operation called with a LWGEOMCOLLECTION type.  This is
unsupported.
HINT:  Change argument 1: 'GEOMETRYCOLLECTION(POINT(1 2),POINT(3 4))'
CONTEXT:  SQL function "st_equals" statement 1

I've tracked this down to errorIfGeometryCollection in
postgis/lwgeom_geos.c. Is this check still necessary? I suspect that
GEOS supports relate operations on geometry collections, e.g., with
shapely:

from shapely.wkt import loads
g1 = loads('GEOMETRYCOLLECTION(POINT(1 2),POINT(3 4))')
g2 = loads('GEOMETRYCOLLECTION(POINT(3 4),POINT(1 2))')
print(g1.equals(g2))  # True
print(g1.relate(g2))  # 0FFFFFFF2

so I'm wondering what is stopping PostGIS from supporting relate
operations with geometry collections?