CREATE FUNCTION create_factor(   p_name VARCHAR(255)
                                    )
RETURNS integer AS $$
DECLARE v_insert_id INTEGER;
BEGIN
    ....
    RETURN v_insert_id AS id;
END;
$$ LANGUAGE plpgsql;

BEGIN;

i create_factor.sql

DO $$
declare factorId integer;

select create_factor into factorId from    /* have tried selecting * as well */
create_factor(
    'my factor'::VARCHAR(255)
);

x

select * from factors where name='my factor' and id=factorId;

x

select k.key_name, v.value from factors f join factor_type_key_store k on k.factor_type_id = f.factor_type_id join factor_key_value_store v on v.factor_type_key_store_id=k.id ;

END$$;

ROLLBACK;