Method build_pushable_cond_for_having_pushdown

sql/sql_lex.cc:12428–12528

*/

bool
st_select_lex::build_pushable_cond_for_having_pushdown(THD *thd, Item *cond)
{
  List<Item> equalities;

  /* Condition can't be pushed */
  if (cond->get_extraction_flag() == MARKER_NO_EXTRACTION)
    return false;

  /**
    Condition can be pushed entirely.
    Transform its multiple equalities and add to attach_to_conds list.
  */
  if (cond->get_extraction_flag() == MARKER_FULL_EXTRACTION)
  {
    Item *result= cond->top_level_transform(thd,
                        &Item::multiple_equality_transformer, (uchar *)this);
    if (!result)
      return true;
    if (result->type() == Item::COND_ITEM &&
        ((Item_cond*) result)->functype() == Item_func::COND_AND_FUNC)
    {
      List_iterator<Item> li(*((Item_cond*) result)->argument_list());
      Item *item;
      while ((item= li++))
      {
        if (attach_to_conds.push_back(item, thd->mem_root))
          return true;
      }
    }
    else
    {
      if (attach_to_conds.push_back(result, thd->mem_root))
        return true;
    }
    return false;
  }

  /**
    There is no flag set for this condition. It means that some
    part of this condition can be pushed.
  */
  if (cond->type() != Item::COND_ITEM)
    return false;

  if (((Item_cond *)cond)->functype() != Item_cond::COND_AND_FUNC)
  {
    /*
      cond is not a conjunctive formula and it cannot be pushed into WHERE.
      Try to extract a formula that can be pushed.
    */
    Item *fix= cond->build_pushable_cond(thd, 0, 0);
    if (!fix)
      return false;
    if (attach_to_conds.push_back(fix, thd->mem_root))
      return true;
  }
  else