Classe « Query »

Méthode sqlalchemy.orm.Query.with_for_update

Signature de la méthode with_for_update

def with_for_update(self, read=False, nowait=False, of=None, skip_locked=False, key_share=False) 

Description

with_for_update.__doc__

return a new :class:`_query.Query`
        with the specified options for the
        ``FOR UPDATE`` clause.

        The behavior of this method is identical to that of
        :meth:`_expression.GenerativeSelect.with_for_update`.
        When called with no arguments,
        the resulting ``SELECT`` statement will have a ``FOR UPDATE`` clause
        appended.  When additional arguments are specified, backend-specific
        options such as ``FOR UPDATE NOWAIT`` or ``LOCK IN SHARE MODE``
        can take effect.

        E.g.::

            q = sess.query(User).populate_existing().with_for_update(nowait=True, of=User)

        The above query on a PostgreSQL backend will render like::

            SELECT users.id AS users_id FROM users FOR UPDATE OF users NOWAIT

        .. note::  It is generally a good idea to combine the use of the
           :meth:`_orm.Query.populate_existing` method when using the
           :meth:`_orm.Query.with_for_update` method.   The purpose of
           :meth:`_orm.Query.populate_existing` is to force all the data read
           from the SELECT to be populated into the ORM objects returned,
           even if these objects are already in the :term:`identity map`.

        .. seealso::

            :meth:`_expression.GenerativeSelect.with_for_update`
            - Core level method with
            full argument and behavioral description.

            :meth:`_orm.Query.populate_existing` - overwrites attributes of
            objects already loaded in the identity map.