Add PARALLEL parameter to functions

scripts-available/CDB_ExtensionUtils.sql

@@ -10,11 +10,11 @@ BEGIN
   sql := 'ALTER EXTENSION cartodb UPDATE TO ''' || ver || '''';
   EXECUTE sql;
 END;
-$$ language 'plpgsql' VOLATILE;
+$$ language 'plpgsql' VOLATILE PARALLEL UNSAFE;
 
 CREATE OR REPLACE FUNCTION cartodb.schema_exists(schema_name text)
 RETURNS boolean AS
 $$
   SELECT EXISTS(SELECT 1 FROM pg_namespace WHERE nspname = schema_name::text);
 $$
-language sql VOLATILE;
+language sql STABLE PARALLEL SAFE;