[postgis-users] ST_Boundary returns MULTIPOLYGON

[Paul Ramsey]

Yes, I could see that as a reasonable interpretation. Just another in
the large collection of corner cases opened up by allowing typed empty
(my fault). The code probably just tests for empty and reflects the
input back in that case.

P.

On Fri, Jan 9, 2015 at 2:26 PM, BladeOfLight16 <bladeoflight16 at gmail.com> wrote:
> Ran across some behavior that seems odd to me:
>
> SELECT ST_AsText(ST_Boundary(geom))
> FROM (VALUES ('POLYGON EMPTY'::GEOMETRY),
>              ('MULTIPOLYGON EMPTY'::GEOMETRY),
>              ('LINESTRING EMPTY'::GEOMETRY),
>              ('MULTILINESTRING EMPTY'::GEOMETRY)
>      ) g (geom);
>
> results in:
>
> 'POLYGON EMPTY'
> 'MULTIPOLYGON EMPTY'
> 'LINESTRING EMPTY'
> 'MULTILINESTRING EMPTY'
>
> Shouldn't the geometry type go down one dimension, despite the fact the
> original was EMPTY? This seems like a minor bug to me. Is it just something
> weird in the OGC specification? I couldn't find anything about it in the
> docs.
>
> Version info:
> PostGIS: POSTGIS="2.1.4 r12966" GEOS="3.4.2-CAPI-1.8.2 r3924" PROJ="Rel.
> 4.8.0, 6 March 2012" GDAL="GDAL 1.11.1, released 2014/09/24" LIBXML="2.7.8"
> LIBJSON="UNKNOWN" RASTER
> PostgreSQL: PostgreSQL 9.3.1, compiled by Visual C++ build 1600, 64-bit
>
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