From PostgreSQL wiki
In many examples in this section, an SQL query produces as output a list of DDL statements to be subsequently executed. This is a fairly common administrative requirement.
The following trivial function allows such queries to be executed directly with no intermediate step. Doing this also takes advantage of PostgreSQL's ability to do transactional DDL; either all changes are made, or all are rolled back. Of course, for safety one would typically do an explicit
BEGIN; first, and inspect the list of commands and, if necessary, the resulting changes to the database, before doing a
CREATE FUNCTION exec(text) returns text language plpgsql volatile AS $f$ BEGIN EXECUTE $1; RETURN $1; END; $f$;