CREATE OR REPLACE FUNCTION export_to_geojson(
  table_name TEXT,
  geom_column TEXT DEFAULT 'geom')
RETURNS TEXT AS
$MAIN$
DECLARE
 json_text text;
BEGIN
 CREATE OR REPLACE FUNCTION row_to_geojson(
   jrow JSONB,
   geom_column TEXT DEFAULT 'geom')
 RETURNS TEXT AS
 $$
 DECLARE
  json_props jsonb;
  json_geom jsonb;
  json_type jsonb;
 BEGIN
  RAISE NOTICE 'jrow = ''%''', jrow;
  RAISE NOTICE 'geom_column = ''%''', geom_column;
  IF NOT jrow ? geom_column THEN
    RAISE EXCEPTION 'geometry column ''%'' is missing', geom_column;
  END IF;
  json_geom := ST_AsGeoJSON((jrow ->> geom_column)::geometry)::jsonb;
  json_geom := jsonb_build_object('geometry', json_geom);
  json_props := jsonb_build_object('properties', jrow - geom_column);
  json_type := jsonb_build_object('type', 'Feature');
  return (json_type || json_geom || json_props)::text;
 END;
 $$
 LANGUAGE plpgsql;
 EXECUTE format('SELECT row_to_geojson(to_jsonb(%I.*), ''%I'') FROM %I', table_name, geom_column, table_name) INTO json_text;
 return (json_text)::text;

END;
$MAIN$
LANGUAGE plpgsql;