Method begin_nested

lib/sqlalchemy/orm/session.py:1993–2017

Begin a "nested" transaction on this Session, e.g. SAVEPOINT. The target database(s) and associated drivers must support SQL SAVEPOINT for this method to function correctly. For documentation on SAVEPOINT transactions, please see :ref:`session_begin_nested`.

(self)

        return trans  # needed for __enter__/__exit__ hook

    def begin_nested(self) -> SessionTransaction:
        """Begin a "nested" transaction on this Session, e.g. SAVEPOINT.

        The target database(s) and associated drivers must support SQL
        SAVEPOINT for this method to function correctly.

        For documentation on SAVEPOINT
        transactions, please see :ref:`session_begin_nested`.

        :return: the :class:`.SessionTransaction` object.  Note that
         :class:`.SessionTransaction` acts as a context manager, allowing
         :meth:`.Session.begin_nested` to be used in a "with" block.
         See :ref:`session_begin_nested` for a usage example.

        .. seealso::

            :ref:`session_begin_nested`

            :ref:`pysqlite_serializable` - special workarounds required
            with the SQLite driver in order for SAVEPOINT to work
            correctly. For asyncio use cases, see the section
            :ref:`aiosqlite_serializable`.

        """
        return self.begin(nested=True)

    def rollback(self) -> None:
        """Rollback the current transaction in progress.