[postgis-tickets] [PostGIS] #3341: Serious rounding issues

[PostGIS]

#3341: Serious rounding issues
--------------------------+---------------------------
  Reporter:  postgispaul  |      Owner:  pramsey
      Type:  defect       |     Status:  closed
  Priority:  medium       |  Milestone:  PostGIS 2.1.9
 Component:  postgis      |    Version:  2.2.x
Resolution:  invalid      |   Keywords:
--------------------------+---------------------------

Comment (by dbaston):

 I was a bit unclear in my earlier comment.  Here is some info on the
 output of ST_Collect:

 {{{
 SELECT ST_GeometryType(ST_Collect(geom)), ST_IsValid(ST_Collect(geom))
 FROM bugreport WHERE id in (600, 1351);
     st_geometrytype    | st_isvalid
 -----------------------+------------
  ST_GeometryCollection | t
 (1 row)
 }}}

 So there is no invalid geometry involved.  What I meant to say what the
 output of ST_Collect, if it were a MultiPolygon (which it is not), would
 be invalid.  I think the issue here is how ST_Difference should be
 handling GeometryCollections, not how it should be handling invalid
 geometries.

 The PostGIS docs for ST_Difference say "Do not call with a
 GeometryCollection as an argument", without any further elaboration, and
 the GEOS headers for Geometry::difference say that it does not support
 GeometryCollections.  So it seems that either:

 * PostGIS should be calling errorIfGeometryCollection(), before passing
 this on to GEOS, or
 * GEOS should be throwing an exception, which PostGIS should handle and
 report an error to the user.  PostGIS is already handling errors from GEOS
 correctly in this case, so it seems that GEOS is not throwing an
 exception.

--
Ticket URL: <https://trac.osgeo.org/postgis/ticket/3341#comment:10>
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