Classe « Session »

Méthode sqlalchemy.orm.Session.get_bind

Signature de la méthode get_bind

def get_bind(self, mapper=None, clause=None, bind=None, _sa_skip_events=None, _sa_skip_for_implicit_returning=False) 

Description

get_bind.__doc__

Return a "bind" to which this :class:`.Session` is bound.

        The "bind" is usually an instance of :class:`_engine.Engine`,
        except in the case where the :class:`.Session` has been
        explicitly bound directly to a :class:`_engine.Connection`.

        For a multiply-bound or unbound :class:`.Session`, the
        ``mapper`` or ``clause`` arguments are used to determine the
        appropriate bind to return.

        Note that the "mapper" argument is usually present
        when :meth:`.Session.get_bind` is called via an ORM
        operation such as a :meth:`.Session.query`, each
        individual INSERT/UPDATE/DELETE operation within a
        :meth:`.Session.flush`, call, etc.

        The order of resolution is:

        1. if mapper given and :paramref:`.Session.binds` is present,
           locate a bind based first on the mapper in use, then
           on the mapped class in use, then on any base classes that are
           present in the ``__mro__`` of the mapped class, from more specific
           superclasses to more general.
        2. if clause given and ``Session.binds`` is present,
           locate a bind based on :class:`_schema.Table` objects
           found in the given clause present in ``Session.binds``.
        3. if ``Session.binds`` is present, return that.
        4. if clause given, attempt to return a bind
           linked to the :class:`_schema.MetaData` ultimately
           associated with the clause.
        5. if mapper given, attempt to return a bind
           linked to the :class:`_schema.MetaData` ultimately
           associated with the :class:`_schema.Table` or other
           selectable to which the mapper is mapped.
        6. No bind can be found, :exc:`~sqlalchemy.exc.UnboundExecutionError`
           is raised.

        Note that the :meth:`.Session.get_bind` method can be overridden on
        a user-defined subclass of :class:`.Session` to provide any kind
        of bind resolution scheme.  See the example at
        :ref:`session_custom_partitioning`.

        :param mapper:
          Optional :func:`.mapper` mapped class or instance of
          :class:`_orm.Mapper`.   The bind can be derived from a
          :class:`_orm.Mapper`
          first by consulting the "binds" map associated with this
          :class:`.Session`, and secondly by consulting the
          :class:`_schema.MetaData`
          associated with the :class:`_schema.Table` to which the
          :class:`_orm.Mapper`
          is mapped for a bind.

        :param clause:
            A :class:`_expression.ClauseElement` (i.e.
            :func:`_expression.select`,
            :func:`_expression.text`,
            etc.).  If the ``mapper`` argument is not present or could not
            produce a bind, the given expression construct will be searched
            for a bound element, typically a :class:`_schema.Table`
            associated with
            bound :class:`_schema.MetaData`.

        .. seealso::

             :ref:`session_partitioning`

             :paramref:`.Session.binds`

             :meth:`.Session.bind_mapper`

             :meth:`.Session.bind_table`