How do I create a nested function in PL/pgSQL?
Nested functions are not supported by PLpgSQL. The emulation has not any sense and it is nonproductive.
Try it:
CREATE OR REPLACE FUNCTION outer() RETURNS void AS $outer$
DECLARE s text;
BEGIN
CREATE OR REPLACE FUNCTION inner() RETURNS text AS $inner$
BEGIN
RETURN 'inner';
END;
$inner$ language plpgsql;
SELECT inner() INTO s;
RAISE NOTICE '%', s;
DROP FUNCTION inner();
END;
$outer$ language plpgsql;
In postgres 9.5 SELECT outer();
outputs
psql:/vagrant/f.sql:14: NOTICE: inner
EDIT: if you don't drop the inner function at the end of the outer function it will remain visible to the rest of the database.