// in PS use own arena or data will be freed after prepare

      if (register_tree_change &&

          thd->stmt_arena->is_stmt_prepare_or_first_stmt_execute())

        arena= thd->activate_stmt_arena_if_needed(&backup);

  /*

      Create Item_func_eq. Note that

      1. this is done on the statement, not execution, arena

      2. if it's a PS then this happens only once - on the first execution.

         On following re-executions, the item will be fix_field-ed normally.

      3. Thus it should be created as if it was fix_field'ed, in particular

         all pointers to items in the execution arena should be protected

         with thd->change_item_tree

    */

    Item_func_eq *item_eq=

      new Item_func_eq(subq_pred->left_expr_orig, subq_lex->ref_pointer_array[0]);

    if (!item_eq)

      DBUG_RETURN(TRUE);

    if (subq_pred->left_expr_orig != subq_pred->left_expr)

      thd->change_item_tree(item_eq->arguments(), subq_pred->left_expr);

    item_eq->in_equality_no= 0;

    sj_nest->sj_on_expr= and_items(sj_nest->sj_on_expr, item_eq);