Method read_initial_values

sql/sql_sequence.cc:623–701

*/

int SEQUENCE::read_initial_values(TABLE *table)
{
  int error= 0;
  enum thr_lock_type save_lock_type;
  MDL_request mdl_request;                      // Empty constructor!
  DBUG_ENTER("SEQUENCE::read_initial_values");

  if (likely(initialized != SEQ_UNINTIALIZED))
    DBUG_RETURN(0);
  write_lock(table);
  if (likely(initialized == SEQ_UNINTIALIZED))
  {
    MYSQL_LOCK *lock;
    bool mdl_lock_used= 0;
    THD *thd= table->in_use;
    bool has_active_transaction= !thd->transaction->stmt.is_empty();
    /*
      There is already a mdl_ticket for this table. However, for list_fields
      the MDL lock is of type MDL_SHARED_HIGH_PRIO which is not usable
      for doing a table lock. Get a proper read lock to solve this.
    */
    if (table->mdl_ticket == 0)
    {
      MDL_request_list mdl_requests;
      mdl_lock_used= 1;
      /*
        This happens if first request is SHOW CREATE TABLE or LIST FIELDS
        where we don't have a mdl lock on the table
      */

      MDL_REQUEST_INIT(&mdl_request, MDL_key::TABLE, table->s->db.str,
                       table->s->table_name.str, MDL_SHARED_READ,
                       MDL_EXPLICIT);
      mdl_requests.push_front(&mdl_request);
      if (thd->mdl_context.acquire_locks(&mdl_requests,
                                         thd->variables.lock_wait_timeout))
      {
        write_unlock(table);
        DBUG_RETURN(HA_ERR_LOCK_WAIT_TIMEOUT);
      }
    }
    save_lock_type= table->reginfo.lock_type;
    table->reginfo.lock_type= TL_READ;
    if (!(lock= mysql_lock_tables(thd, &table, 1,
                                  MYSQL_LOCK_IGNORE_GLOBAL_READ_ONLY)))
    {
      if (mdl_lock_used)
        thd->mdl_context.release_lock(mdl_request.ticket);
      write_unlock(table);

      if (!has_active_transaction && !thd->transaction->stmt.is_empty() &&
          !thd->in_sub_stmt)
        trans_commit_stmt(thd);
      DBUG_RETURN(HA_ERR_LOCK_WAIT_TIMEOUT);
    }
    DBUG_ASSERT(table->reginfo.lock_type == TL_READ);
    if (likely(!(error= read_stored_values(table))))
      initialized= SEQ_READY_TO_USE;