Expression_cache_tracker* Item_cache_wrapper::init_tracker(MEM_ROOT *mem_root)
{
  if (expr_cache)
  {
    Expression_cache_tracker* tracker=
      new(mem_root) Expression_cache_tracker(expr_cache);
    if (tracker)
      ((Expression_cache_tmptable *)expr_cache)->set_tracker(tracker);
    return tracker;
  }
  return NULL;
}
Expression_cache_tracker* Item_cache_wrapper::init_tracker(MEM_ROOT *mem_root)
{
  if (expr_cache)
  {
    Expression_cache_tracker* tracker=
      new(mem_root) Expression_cache_tracker(expr_cache);
    if (tracker)
      ((Expression_cache_tmptable *)expr_cache)->set_tracker(tracker);
    return tracker;
  }
  return NULL;
}