PostGIS  2.1.10dev-r@@SVN_REVISION@@
PG_FUNCTION_INFO_V1 ( LWGEOM_isclosed  )

IsClosed(GEOMETRY) if geometry is a linestring then returns startpoint == endpoint.

If its not a linestring then return NULL. If it's a collection containing multiple linestrings,

Returns
true only if all the linestrings have startpoint=endpoint.