Function create_hj_key_for_table

sql/sql_select.cc:13554–13662

*/

static bool create_hj_key_for_table(JOIN *join, JOIN_TAB *join_tab,
                                    KEYUSE *org_keyuse, table_map used_tables)
{
  KEY *keyinfo;
  KEY_PART_INFO *key_part_info;
  KEYUSE *keyuse= org_keyuse;
  uint key_parts= 0;
  THD  *thd= join->thd;
  TABLE *table= join_tab->table;
  bool first_keyuse= TRUE;
  DBUG_ENTER("create_hj_key_for_table");

  do
  {
    if (!(~used_tables & keyuse->used_tables) &&
        join_tab->keyuse_is_valid_for_access_in_chosen_plan(join, keyuse) &&
        are_tables_local(join_tab, keyuse->used_tables))    
    {
      if (first_keyuse)
      {
        key_parts++;
      }
      else
      {
        KEYUSE *curr= org_keyuse;
        for( ; curr < keyuse; curr++)
        {
          if (curr->keypart == keyuse->keypart &&
              !(~used_tables & curr->used_tables) &&
              join_tab->keyuse_is_valid_for_access_in_chosen_plan(join,
                                                                  curr) &&
              are_tables_local(join_tab, curr->used_tables))
            break;
        }
        if (curr == keyuse)
           key_parts++;
      }
    }
    first_keyuse= FALSE;
    keyuse++;
  } while (keyuse->table == table && keyuse->is_for_hash_join());
  if (!key_parts)
    DBUG_RETURN(TRUE);
  /* This memory is allocated only once for the joined table join_tab */
  if (!(keyinfo= thd->alloc<KEY>(1)) ||
      !(key_part_info = thd->alloc<KEY_PART_INFO>(key_parts)))
    DBUG_RETURN(TRUE);
  keyinfo->usable_key_parts= keyinfo->user_defined_key_parts = key_parts;
  keyinfo->ext_key_parts= keyinfo->user_defined_key_parts;
  keyinfo->key_part= key_part_info;
  keyinfo->key_length=0;
  keyinfo->algorithm= HA_KEY_ALG_UNDEF;
  keyinfo->flags= HA_GENERATED_KEY;
  keyinfo->is_statistics_from_stat_tables= FALSE;
  keyinfo->all_nulls_key_parts= 0;
  keyinfo->stat_storage_length= 0;
  keyinfo->name.str= "$hj";
  keyinfo->name.length= 3;