[PostGIS] #6136: ST_MakeValid merges polygons in a MultiPolygon.

[PostGIS]

#6136: ST_MakeValid merges polygons in a MultiPolygon.
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  Reporter:  Lars Aksel Opsahl  |      Owner:  pramsey
      Type:  defect             |     Status:  new
  Priority:  medium             |  Milestone:  PostGIS 3.6.5
 Component:  postgis            |    Version:  3.6.x
Resolution:                     |   Keywords:
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Comment (by Lars Aksel Opsahl):

 We often use ST_MakeValid(geom) before calling functions such as
 ST_Intersection().

 However, for invalid MULTIPOLYGON and ST_MakeValid() we may end up with
 ST_Union() effect as we show here.

 If the goal is simply to ensure that each polygon is individually valid,
 then ST_MakeValid(ST_ForceCollection(geom)) appears to be the correct
 approach when MULTIPOLYGONs are involved, as it validates each polygon
 independently rather than the MULTIPOLYGON as a whole as it seems.
-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/6136#comment:2>
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