I was using TRANSFORM USING with Hive 0.8.1, and noticed that this is invalid syntax:
TRANSFORM USING
SELECT a, TRANSFORM(b, c) USING \'fake.py\' AS d,
Apparently this is not possible. The fake.py has to handle that as well, i.e. one must do
fake.py
SELECT TRANSFORM(a, b, c) USING 'fake.py' AS a, d FROM test_table;
and make it so that fake.py does output 'a' as well.