LP:801560 - ST_UNION of adjacent polygons includes extra line in maria-5.3-gis

The ST_UNION of two polygons that share a common edge is a polygon that contains that edge as a redundant line.

Example:

SELECT AsText( ST_UNION(
PolygonFromText(' POLYGON( ( 2 2 , 3 2 , 7 5 , 2 0 , 2 2 ) ) ') ,
PolygonFromText(' POLYGON( ( 2 2 , 3 2 , 3 3 , 2 5 , 2 2 ) ) ') ) );

Returns POLYGON((2 0,2 2,3 2,2 2,2 5,3 3,3 2,7 5,2 0))

Note that the list includes "2 2,3 2,2 2"

whereas postgis returns the correct POLYGON((3 2,7 5,2 0,2 2,2 5,3 3,3 2))