text: create table foo (a char(10), b varchar(10));
  insert into foo values ('1234567890', '1234567890');
  
  -- should give an error (constant expressions cannot be used as function index)
  create index i_foo_trans_a_b on foo (translate(a, b, null));
  drop index i_foo_trans_a_b on foo;
  
  create index i_foo_trans_a_b on foo (translate(a, null, b));
  drop index i_foo_trans_a_b on foo;
  
  create index i_foo_trans_a_b on foo (translate(null, a, b));
  drop index i_foo_trans_a_b on foo;
  
  -- should work
  create index i_foo_trans_a_b on foo (translate(a, a, b));
  drop index i_foo_trans_a_b on foo;
  
  
  -- should return null and give no error
  select translate(a, b, null) from foo;
  select translate(a, null, b) from foo;
  select translate(null, a, b) from foo;
  
  drop foo;
  
  -- should give an error (constant expressions cannot be used as function index)
  create table foo (a int);
  create index idx on foo(5);
  drop foo;
  