def swap_tables()

in core/lib/payload/copy.py [0:0]

• 26 lines of code
• 3 McCabe index (conditional complexity)

    def swap_tables(self):
        """
        Flip the table name while holding the write lock. All operations
        during this stage will be executed inside a single transaction.
        """
        if self.stop_before_swap:
            return True
        log.info("== Stage 6: Swap table ==")
        self.stop_slave_sql()
        self.execute_sql(sql.set_session_variable("autocommit"), (0,))
        self.start_transaction()
        stage_start_time = time.time()
        self.lock_tables((self.new_table_name, self.table_name, self.delta_table_name))
        log.info("Final round of replay before swap table")
        self.replay_changes(single_trx=True, holding_locks=True)
        # We will not run delta checksum here, because there will be an error
        # like this, if we run a nested query using `NOT EXISTS`:
        # SQL execution error: [1100] Table 't' was not locked with LOCK TABLES
        self.execute_sql(sql.rename_table(self.table_name, self.renamed_table_name))
        self.table_swapped = True
        self.add_drop_table_entry(self.renamed_table_name)
        self.execute_sql(sql.rename_table(self.new_table_name, self.table_name))
        log.info("Table has successfully swapped, new schema takes effect now")
        self._cleanup_payload.remove_drop_table_entry(
            self._current_db, self.new_table_name
        )
        self.commit()
        self.unlock_tables()
        self.stats["time_in_lock"] = self.stats.setdefault("time_in_lock", 0) + (
            time.time() - stage_start_time
        )
        self.execute_sql(sql.set_session_variable("autocommit"), (1,))
        self.start_slave_sql()