[postgis-tickets] [PostGIS] #4541: ST_ConcaveHull returns a "geometrycollection" type instead of the expected "polygon"

[PostGIS]

#4541: ST_ConcaveHull returns a "geometrycollection" type instead of the expected
"polygon"
---------------------+---------------------------
 Reporter:  v89461   |      Owner:  pramsey
     Type:  defect   |     Status:  new
 Priority:  blocker  |  Milestone:  PostGIS 2.5.4
Component:  postgis  |    Version:  2.5.x
 Keywords:           |
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 Ran into an unexpected behaviour of `ST_ConcaveHull` during a migration
 from 2.4 to 2.5.

 The [https://postgis.net/docs/ST_ConcaveHull.html documentation] doesn't
 specify the geometry type it returns but I assume it is a `POLYGON`.


 Using `POSTGIS="2.4.5 r16765" PGSQL="96" GEOS="3.6.3-CAPI-1.10.3 80c13047"
 PROJ="Rel. 4.9.3, 15 August 2016" GDAL="GDAL 1.9.2, released 2012/10/08"
 LIBXML="2.7.6" LIBJSON="0.11" RASTER`

 With the attached `ST_ConcaveHull` query I get a `POLYGON` result, as
 expected.

 Using `POSTGIS="2.5.2 r17328" [EXTENSION] PGSQL="110"
 GEOS="3.7.0-CAPI-1.11.0 673b9939" PROJ="Rel. 5.2.0, September 15th, 2018"
 GDAL="GDAL 2.3.1, released 2018/06/22" LIBXML="2.9.1" LIBJSON="0.12"
 LIBPROTOBUF="1.3.0" RASTER`

 With the attached `ST_ConcaveHull` query I get a strange
 `GEOMETRYCOLLECTION` made of several `POINT` and ending with a `POLYGON`.

 Maybe it is a string length issue because I get a `POLYGON` as expected if
 I remove the first or last point of the query, or if I "round" the values
 by removing the `00000001` floating point approximations.

-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/4541>
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