PostGIS

ST_NumPoints — Returns the number of points in a LineString or CircularString.

+integer +ST_NumPoints(+`geometry `+g1`)`;

Return the number of points in an ST_LineString or ST_CircularString value. Prior to 1.4 only works with linestrings as the specs state. From 1.4 forward this is an alias for ST_NPoints which returns number of vertexes for not just linestrings. Consider using ST_NPoints instead which is multi-purpose and works with many geometry types.

[.inlinemediaobject] This method implements the OGC Simple Features Implementation Specification for SQL 1.1.

This method implements the SQL/MM specification. SQL-MM 3: 7.2.4

ST_NPoints