[postgis-tickets] [PostGIS] #2377: ST_CollectionHomogenize forms invalid polygons

[PostGIS]

#2377: ST_CollectionHomogenize forms invalid polygons
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 Reporter:  robe     |       Owner:  pramsey      
     Type:  defect   |      Status:  new          
 Priority:  medium   |   Milestone:  PostGIS 2.1.1
Component:  postgis  |     Version:  2.0.x        
 Keywords:           |  
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Description changed by robe:

Old description:

> {{{
> SELECT
>     ST_IsValid(ST_CollectionHomogenize(ST_Split(g1.geom1, g1.geom2)))
>
> FROM (SELECT
>   ST_GeomFromText('POLYGON((2 4.5,3 2.6,3 1.8,2 0,-1.5 2.2,
>    0.056 3.222,-1.5 4.2,2 6.5,2 4.5))') As geom1,
> ST_GeomFromText('LINESTRING(-0.62 5.84,-0.8 0.59)') As geom2) AS g1;
> }}}
>

> For example the above geometry collection consisting of only polygons --
> ST_CollectionHomogenize converts to an invalid multipolygon.  It's of
> course invalid because the polygons have shred edges.

New description:

 {{{
 SELECT
     ST_IsValid(ST_CollectionHomogenize(ST_Split(g1.geom1, g1.geom2)))

 FROM (SELECT
   ST_GeomFromText('POLYGON((2 4.5,3 2.6,3 1.8,2 0,-1.5 2.2,
    0.056 3.222,-1.5 4.2,2 6.5,2 4.5))') As geom1,
 ST_GeomFromText('LINESTRING(-0.62 5.84,-0.8 0.59)') As geom2) AS g1;
 }}}


 For example the above geometry collection consisting of only polygons --
 ST_CollectionHomogenize converts to an invalid multipolygon.  It's of
 course invalid because the polygons have shared edges.

--

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Ticket URL: <http://trac.osgeo.org/postgis/ticket/2377#comment:2>
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