Function save_window_function_values

sql/sql_window.cc:2796–2838

Helper function that takes a list of window functions and writes their values in the current table record. */

  their values in the current table record.
*/
static
bool save_window_function_values(List<Item_window_func>& window_functions,
                                 TABLE *tbl, uchar *rowid_buf)
{
  List_iterator_fast<Item_window_func> iter(window_functions);
  JOIN_TAB *join_tab= tbl->reginfo.join_tab;
  tbl->file->ha_rnd_pos(tbl->record[0], rowid_buf);
  store_record(tbl, record[1]);
  while (Item_window_func *item_win= iter++)
    item_win->save_in_field(item_win->result_field, true);

  /*
    In case we have window functions present, an extra step is required
    to compute all the fields from the temporary table.
    In case we have a compound expression such as: expr + expr,
    where one of the terms has a window function inside it, only
    after computing window function values we actually know the true
    final result of the compounded expression.

    Go through all the func items and save their values once again in the
    corresponding temp table fields. Do this for each row in the table.

    This needs to be done earlier because ORDER BY clause can also have
    a window function, so we need to make sure all the fields of the temp.table
    are updated before we do the filesort. So is best to update the other fields
    that contain the window functions along with the computation of window
    functions.
  */

  Item **func_ptr= join_tab->tmp_table_param->items_to_copy;
  Item *func;
  for (; (func = *func_ptr) ; func_ptr++)
  {
    if (func->with_window_func() && func->type() != Item::WINDOW_FUNC_ITEM)
      func->save_in_result_field(true);
  }

  int err= tbl->file->ha_update_row(tbl->record[1], tbl->record[0]);
  if (err && err != HA_ERR_RECORD_IS_THE_SAME)
    return true;

  return false;
}

/*
  TODO(cvicentiu) update this comment to reflect the new execution.