Function join_read_key2

sql/sql_select.cc:25367–25430

eq_ref access handler but generalized a bit to support TABLE and TABLE_REF not from the join_tab. See join_read_key for detailed synopsis. */

  not from the join_tab. See join_read_key for detailed synopsis.
*/
int join_read_key2(THD *thd, JOIN_TAB *tab, TABLE *table, TABLE_REF *table_ref)
{
  int error;
  if (!table->file->inited)
  {
    error= table->file->ha_index_init(table_ref->key, tab ? tab->sorted : TRUE);
    if (unlikely(error))
    {
      (void) report_error(table, error);
      return 1;
    }
  }

  /*
    The following is needed when one makes ref (or eq_ref) access from row
    comparisons: one must call row->bring_value() to get the new values.
  */
  if (tab && tab->bush_children)
  {
    TABLE_LIST *emb_sj_nest= tab->bush_children->start->emb_sj_nest;
    emb_sj_nest->sj_subq_pred->left_exp()->bring_value();
  }

  /* TODO: Why don't we do "Late NULLs Filtering" here? */

  if (cmp_buffer_with_ref(thd, table, table_ref) ||
      (table->status & (STATUS_GARBAGE | STATUS_NO_PARENT | STATUS_NULL_ROW)))
  {
    if (table_ref->key_err)
    {
      table->status=STATUS_NOT_FOUND;
      return -1;
    }
    /*
      Moving away from the current record. Unlock the row
      in the handler if it did not match the partial WHERE.
    */
    if (tab && tab->ref.has_record && tab->ref.use_count == 0)
    {
      tab->read_record.table->file->unlock_row();
      table_ref->has_record= FALSE;
    }
    error=table->file->ha_index_read_map(table->record[0],
                                  table_ref->key_buff,
                                  make_prev_keypart_map(table_ref->key_parts),
                                  HA_READ_KEY_EXACT);
    if (unlikely(error) &&
        error != HA_ERR_KEY_NOT_FOUND && error != HA_ERR_END_OF_FILE)
      return report_error(table, error);

    if (likely(!error))
    {
      table_ref->has_record= TRUE;
      table_ref->use_count= 1;
    }
  }
  else if (table->status == 0)
  {