ST_NumPoints

Calculates the number of vertices of a spatial object, empty objects return NULL.

The first and last vertex of polygons and multipolygons are counted separately.

Behavior type

Syntax

ST_NumPoints( g )

Arguments

g

Spatial object for which you want to count the vertices, type GEOMETRY or GEOGRAPHY

Returns

INTEGER

Supported data types

Examples

The following examples show how to use ST_NumPoints.

Returns the number of vertices in a linestring:

=> SELECT ST_NumPoints(ST_GeomFromText('LINESTRING(1.33 1.56,2.31 3.4,2.78 5.82,
   3.76 3.9,4.11 3.27,5.85 4.34,6.9 4.231,7.61 5.77)'));
 ST_NumPoints
--------------
            8
(1 row)

Use ST_Boundary and ST_NumPoints to return the number of vertices of a polygon:

=> SELECT ST_NumPoints(ST_Boundary(ST_GeomFromText('POLYGON((1 2,1 4,
   2 5,3 6,4 6,5 5,4 4,3 3,1 2))')));
 ST_NumPoints
--------------
            9
(1 row)