PostGIS
2.5.0beta2devr@@SVN_REVISION@@

PG_FUNCTION_INFO_V1  (  LWGEOM_length_linestring  ) 
find the "length of a geometry" length(point) = 0 length(line) = length of line length(polygon) = 0 – could make sense to return sum(ring perimeter) uses euclidian 3d/2d length depending on input dimensions.