This parameter is normally on. When set to
off, it disables validation of the routine body string during sql-createfunction and sql-createprocedure. Disabling validation avoids side effects of the validation process, in particular preventing false positives due to problems such as forward references. Set this parameter to
off before loading functions on behalf of other users; pg_dump does so automatically.
You only really want to turn this off to resolve circular dependancies, and that can be done on a per-session basis. In general, checking for syntax errors in PL/pgSQL functions is a very good idea.