Method yield_per

lib/sqlalchemy/orm/query.py:1035–1058

r"""Yield only ``count`` rows at a time. The purpose of this method is when fetching very large result sets (> 10K rows), to batch results in sub-collections and yield them out partially, so that the Python interpreter doesn't need to declare very large areas of memo

(self, count: int)

    @_generative
    def yield_per(self, count: int) -> Self:
        r"""Yield only ``count`` rows at a time.

        The purpose of this method is when fetching very large result sets
        (> 10K rows), to batch results in sub-collections and yield them
        out partially, so that the Python interpreter doesn't need to declare
        very large areas of memory which is both time consuming and leads
        to excessive memory use.   The performance from fetching hundreds of
        thousands of rows can often double when a suitable yield-per setting
        (e.g. approximately 1000) is used, even with DBAPIs that buffer
        rows (which are most).

        As of SQLAlchemy 1.4, the :meth:`_orm.Query.yield_per` method is
        equivalent to using the ``yield_per`` execution option at the ORM
        level. See the section :ref:`orm_queryguide_yield_per` for further
        background on this option.

        .. seealso::

            :ref:`orm_queryguide_yield_per`

        """
        self.load_options += {"_yield_per": count}
        return self

    @util.became_legacy_20(
        ":meth:`_orm.Query.get`",