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Classe « Result »

Méthode sqlalchemy.Result.yield_per

Signature de la méthode yield_per

def yield_per(self, num: 'int') -> 'Self' 

Description

help(Result.yield_per)

Configure the row-fetching strategy to fetch ``num`` rows at a time.

This impacts the underlying behavior of the result when iterating over
the result object, or otherwise making use of  methods such as
:meth:`_engine.Result.fetchone` that return one row at a time.   Data
from the underlying cursor or other data source will be buffered up to
this many rows in memory, and the buffered collection will then be
yielded out one row at a time or as many rows are requested. Each time
the buffer clears, it will be refreshed to this many rows or as many
rows remain if fewer remain.

The :meth:`_engine.Result.yield_per` method is generally used in
conjunction with the
:paramref:`_engine.Connection.execution_options.stream_results`
execution option, which will allow the database dialect in use to make
use of a server side cursor, if the DBAPI supports a specific "server
side cursor" mode separate from its default mode of operation.

.. tip::

    Consider using the
    :paramref:`_engine.Connection.execution_options.yield_per`
    execution option, which will simultaneously set
    :paramref:`_engine.Connection.execution_options.stream_results`
    to ensure the use of server side cursors, as well as automatically
    invoke the :meth:`_engine.Result.yield_per` method to establish
    a fixed row buffer size at once.

    The :paramref:`_engine.Connection.execution_options.yield_per`
    execution option is available for ORM operations, with
    :class:`_orm.Session`-oriented use described at
    :ref:`orm_queryguide_yield_per`. The Core-only version which works
    with :class:`_engine.Connection` is new as of SQLAlchemy 1.4.40.

.. versionadded:: 1.4

:param num: number of rows to fetch each time the buffer is refilled.
 If set to a value below 1, fetches all rows for the next buffer.

.. seealso::

    :ref:`engine_stream_results` - describes Core behavior for
    :meth:`_engine.Result.yield_per`

    :ref:`orm_queryguide_yield_per` - in the :ref:`queryguide_toplevel`

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