ST_Union(geom[]) doesn't union single member arrays

[pramsey]

Compare

select
 st_asewkt(
   st_union(
     array[
       st_geomfromtext(
         'GEOMETRYCOLLECTION(
           POLYGON((0 0,10 0,25 25,0 10,0 0)),
           POLYGON((20 20,30 20,30 30,20 30,20 20))
         )'
       )
     ]
   )
 )

and

select
 st_asewkt(
   st_union(
     array[
       st_geomfromtext(
         'GEOMETRYCOLLECTION(
           POLYGON((0 0,10 0,25 25,0 10,0 0)),
           POLYGON((20 20,30 20,30 30,20 30,20 20))
         )'
       ),
       st_geomfromtext(
         'GEOMETRYCOLLECTION(
           POLYGON((100 100, 110 100, 110 110, 100 100))
         )'
       )
     ]
   )
 )

[pramsey]

See also ​https://lists.osgeo.org/pipermail/postgis-devel/2024-February/030259.html

[Paul Ramsey <pramsey@…>]

In 15c8d95/git:

Union the contents of a single-member array before returning, so that collections get flattened. References #5677

[Paul Ramsey <pramsey@…>]

In f37390b/git:

ST_Union(geom[]) should unary union single entry arrays
References #5677

[Paul Ramsey <pramsey@…>]

In b885f39b/git:

ST_Union(geom[]) should unary union single entry arrays
References #5677

[Paul Ramsey <pramsey@…>]

In bd10d04/git:

ST_Union(geom[]) should unary union single entry arrays
References #5677