Returns the convex hull of the geometry value.
SELECT NEW ST_MultiPoint('MultiPoint( (1 1), (2 2), (5 3), (7 2), (9 3), (8 4), (6 6), (6 9), (4 9), (1 5) )').ST_ConvexHull()
The following example returns the single point (0,0). The convex hull of a single point is a point.
SELECT NEW ST_Point(0,0).ST_ConvexHull()
The following example returns the result LineString (0 0, 3 3). The convex hull of a single straight line is a linestring with a single segment.
SELECT NEW ST_LineString('LineString(0 0,1 1,2 2,3 3)').ST_ConvexHull()
SQL/MM (ISO/IEC 13249-3: 2006) 5.1.16