item_sum.cc:

  DBUG_ENTER("Item_sum_distinct::setup");

  /* It's legal to call setup() more than once when in a subquery */

  if (tree)

    return FALSE;

    DBUG_RETURN(FALSE);

  /*

    Virtual table and the tree are created anew on each re-execution of

    mem_root.

  */

  if (field_list.push_back(&field_def))

    return TRUE;

    DBUG_RETURN(TRUE);

  null_value= maybe_null= 1;

  quick_group= 0;

                               args[0]->unsigned_flag);

  if (! (table= create_virtual_tmp_table(thd, field_list)))

    return TRUE;

    DBUG_RETURN(TRUE);

  /* XXX: check that the case of CHAR(0) works OK */

  tree_key_length= table->s->reclength - table->s->null_bytes;