Classe « Session »

Méthode sqlalchemy.orm.Session.refresh

Signature de la méthode refresh

def refresh(self, instance, attribute_names=None, with_for_update=None) 

Description

refresh.__doc__

Expire and refresh attributes on the given instance.

        The selected attributes will first be expired as they would when using
        :meth:`_orm.Session.expire`; then a SELECT statement will be issued to
        the database to refresh column-oriented attributes with the current
        value available in the current transaction.

        :func:`_orm.relationship` oriented attributes will also be immediately
        loaded if they were already eagerly loaded on the object, using the
        same eager loading strategy that they were loaded with originally.
        Unloaded relationship attributes will remain unloaded, as will
        relationship attributes that were originally lazy loaded.

        .. versionadded:: 1.4 - the :meth:`_orm.Session.refresh` method
           can also refresh eagerly loaded attributes.

        .. tip::

            While the :meth:`_orm.Session.refresh` method is capable of
            refreshing both column and relationship oriented attributes, its
            primary focus is on refreshing of local column-oriented attributes
            on a single instance. For more open ended "refresh" functionality,
            including the ability to refresh the attributes on many objects at
            once while having explicit control over relationship loader
            strategies, use the
            :ref:`populate existing <orm_queryguide_populate_existing>` feature
            instead.

        Note that a highly isolated transaction will return the same values as
        were previously read in that same transaction, regardless of changes
        in database state outside of that transaction.   Refreshing
        attributes usually only makes sense at the start of a transaction
        where database rows have not yet been accessed.

        :param attribute_names: optional.  An iterable collection of
          string attribute names indicating a subset of attributes to
          be refreshed.

        :param with_for_update: optional boolean ``True`` indicating FOR UPDATE
          should be used, or may be a dictionary containing flags to
          indicate a more specific set of FOR UPDATE flags for the SELECT;
          flags should match the parameters of
          :meth:`_query.Query.with_for_update`.
          Supersedes the :paramref:`.Session.refresh.lockmode` parameter.

        .. seealso::

            :ref:`session_expire` - introductory material

            :meth:`.Session.expire`

            :meth:`.Session.expire_all`

            :ref:`orm_queryguide_populate_existing` - allows any ORM query
            to refresh objects as they would be loaded normally.