DROP TABLE IF EXISTS ambiguous_table;
CREATE TABLE ambiguous_table(which text);
INSERT INTO ambiguous_table VALUES ('permanent');
CREATE OR REPLACE FUNCTION ss () RETURNS text LANGUAGE plpgsql AS $$
BEGIN
  RETURN which FROM ambiguous_table;
END;
$$;

-- Returns 'permanent'
SELECT ss();

-- Replace the table in 'public' schema with a temp table
DROP TABLE ambiguous_table;
CREATE TEMP TABLE ambiguous_table(which text);
INSERT INTO ambiguous_table VALUES ('temp');

-- Should return 'temp', but fails if pg_temp wasn't initialized
-- before executing the function the first time.
SELECT ss();