[postgis-tickets] [PostGIS] #4182: Unexpected TopologyException during ST_Union aggregate function with valid polygons

[PostGIS]

#4182: Unexpected TopologyException during ST_Union aggregate function with valid
polygons
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  Reporter:  blaggner  |      Owner:  pramsey
      Type:  defect    |     Status:  new
  Priority:  medium    |  Milestone:  PostGIS GEOS
 Component:  postgis   |    Version:  2.3.x
Resolution:            |   Keywords:
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Comment (by mdavis):

 Thanks for the test case.  It does indeed trigger the error, in GEOS and
 in JTS.

 The reason for the error is that there are a LOT of "slivers" in the
 dataset - i.e. polygons whose boundaries almost line up, but not quite
 (the vertices are very slightly different to the adjacent polygon).

 The good news is that this should be handled by the forthcoming overlay
 code.  The bad news is that the slivers will very much show up in the
 output (typically as tiny holes in the middle of a large unioin polygon.
 This may or may not be an issue depending on your intended use of the
 data.

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Ticket URL: <https://trac.osgeo.org/postgis/ticket/4182#comment:6>
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