On 2024-12-22 15:44 +0100, Luca Bertoncello wrote: > > I suppose, in the last versions of PostGIS the Function ST_Makevalid > > will return something other than in the previous one. > > Some information more... > > It seems, in some cases, the function ST_Makevalid returns > ST_GeometryCollection instead of ST_MultiPolygon... > Why?!?
See "dimensional collapse" on https://postgis.net/docs/ST_MakeValid.html ST_MakeValid creates (multi)linestring and/or (multi)point geometries in your case. You can also try the structure algorithm with params 'method=structure keepcollapsed=false' and avoid ST_CollectionExtract. But the linework and structure algorithms do not necessarily return the same geometries, see the examples in the ST_MakeValid docs. -- Erik Wienhold
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