ST_Summary — Returns a text summary of the contents of a geometry.
text ST_Summary(geometry  g);
text ST_Summary(geography  g);
Returns a text summary of the contents of the geometry.
Flags shown square brackets after the geometry type have the following meaning:
M: has M coordinate
Z: has Z coordinate
B: has a cached bounding box
G: is geodetic (geography)
S: has spatial reference system
 This method supports Circular Strings and Curves
 This function supports Polyhedral surfaces.
 This function supports Triangles and Triangulated Irregular Network Surfaces (TIN).
Availability: 1.2.2
Enhanced: 2.0.0 added support for geography
Enhanced: 2.1.0 S flag to denote if has a known spatial reference system
Enhanced: 2.2.0 Added support for TIN and Curves
=# SELECT ST_Summary(ST_GeomFromText('LINESTRING(0 0, 1 1)')) as geom,
        ST_Summary(ST_GeogFromText('POLYGON((0 0, 1 1, 1 2, 1 1, 0 0))')) geog;
            geom             |          geog
-----------------------------+--------------------------
 LineString[B] with 2 points | Polygon[BGS] with 1 rings
                             | ring 0 has 5 points
                             :
(1 row)
=# SELECT ST_Summary(ST_GeogFromText('LINESTRING(0 0 1, 1 1 1)')) As geog_line,
        ST_Summary(ST_GeomFromText('SRID=4326;POLYGON((0 0 1, 1 1 2, 1 2 3, 1 1 1, 0 0 1))')) As geom_poly;
;
           geog_line             |        geom_poly
-------------------------------- +--------------------------
 LineString[ZBGS] with 2 points | Polygon[ZBS] with 1 rings
                                :    ring 0 has 5 points
                                :
(1 row)