Classe « Session »

Méthode sqlalchemy.orm.Session.bulk_update_mappings

Signature de la méthode bulk_update_mappings

def bulk_update_mappings(self, mapper, mappings) 

Description

bulk_update_mappings.__doc__

Perform a bulk update of the given list of mapping dictionaries.

        The bulk update feature allows plain Python dictionaries to be used as
        the source of simple UPDATE operations which can be more easily
        grouped together into higher performing "executemany"
        operations.  Using dictionaries, there is no "history" or session
        state management features in use, reducing latency when updating
        large numbers of simple rows.

        .. versionadded:: 1.0.0

        .. warning::

            The bulk update feature allows for a lower-latency UPDATE
            of rows at the expense of most other unit-of-work features.
            Features such as object management, relationship handling,
            and SQL clause support are **silently omitted** in favor of raw
            UPDATES of records.

            Please note that newer versions of SQLAlchemy are **greatly
            improving the efficiency** of the standard flush process. It is
            **strongly recommended** to not use the bulk methods as they
            represent a forking of SQLAlchemy's functionality and are slowly
            being moved into legacy status.  New features such as
            :ref:`orm_dml_returning_objects` are both more efficient than
            the "bulk" methods and provide more predictable functionality.

            **Please read the list of caveats at**
            :ref:`bulk_operations_caveats` **before using this method, and
            fully test and confirm the functionality of all code developed
            using these systems.**

        :param mapper: a mapped class, or the actual :class:`_orm.Mapper`
         object,
         representing the single kind of object represented within the mapping
         list.

        :param mappings: a sequence of dictionaries, each one containing the
         state of the mapped row to be updated, in terms of the attribute names
         on the mapped class.   If the mapping refers to multiple tables, such
         as a joined-inheritance mapping, each dictionary may contain keys
         corresponding to all tables.   All those keys which are present and
         are not part of the primary key are applied to the SET clause of the
         UPDATE statement; the primary key values, which are required, are
         applied to the WHERE clause.


        .. seealso::

            :ref:`bulk_operations`

            :meth:`.Session.bulk_insert_mappings`

            :meth:`.Session.bulk_save_objects`