Add PARALLEL parameter to functions

scripts-available/CDB_ZoomFromScale.sql

@@ -2,7 +2,7 @@
 CREATE OR REPLACE FUNCTION _CDB_MaxSupportedZoom()
 RETURNS int
 LANGUAGE SQL
-IMMUTABLE
+IMMUTABLE PARALLEL SAFE
 AS $$
   -- The maximum zoom level has to be limited for various reasons,
   -- e.g. zoom levels greater than 31 would require tile coordinates
@@ -15,7 +15,7 @@ $$;
 CREATE OR REPLACE FUNCTION cartodb.CDB_ZoomFromScale(scaleDenominator numeric)
 RETURNS int
 LANGUAGE SQL
-IMMUTABLE
+IMMUTABLE PARALLEL SAFE
 AS $$
   SELECT
     CASE