def nextID ( self, ch ):
    """Get an new identifier. This is it's own txn and should not be called inside another transaction."""

    with closing(self.conn.cursor()) as cursor:
    
      # LOCK the table to prevent race conditions on the ID
      sql = "LOCK TABLES {} WRITE".format(ch.getIdsTable())
      try:

        cursor.execute ( sql )

        # Query the current max identifier
        sql = "SELECT max(id) FROM {}".format(ch.getIdsTable()) 
        try:
          cursor.execute ( sql )
        except MySQLdb.Error, e:
          logger.error ( "Failed to create annotation identifier {}: {}. sql={}".format(e.args[0], e.args[1], sql))
          raise

        # Here we've queried the highest id successfully    
        row = cursor.fetchone ()
        # if the table is empty start at 1, 0 is no 
        if ( row[0] == None ):
          identifier = 1
        else:
          identifier = int ( row[0] ) + 1

        # increment and update query
        sql = "INSERT INTO {} VALUES ({})".format(ch.getIdsTable(), identifier)
        try:
          cursor.execute ( sql )
        except MySQLdb.Error, e:
          logger.error ( "Failed to insert into identifier table: {}: {}. sql={}".format(e.args[0], e.args[1], sql))
          raise

      finally:
        sql = "UNLOCK TABLES" 
        cursor.execute ( sql )
        self.conn.commit()

      return identifier
dataset/ETHPy150Open neurodata/ndstore/ocpca/ocpcadb.py/OCPCADB.nextID/original