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Classe « SessionEvents »

Méthode sqlalchemy.orm.SessionEvents.do_orm_execute

Signature de la méthode do_orm_execute

def do_orm_execute(self, orm_execute_state: 'ORMExecuteState') -> 'None' 

Description

help(SessionEvents.do_orm_execute)

Intercept statement executions that occur on behalf of an
ORM :class:`.Session` object.

.. container:: event_signatures

     Example argument forms::

        from sqlalchemy import event


        @event.listens_for(SomeSessionClassOrObject, 'do_orm_execute')
        def receive_do_orm_execute(orm_execute_state):
            "listen for the 'do_orm_execute' event"

            # ... (event handling logic) ...


This event is invoked for all top-level SQL statements invoked from the
:meth:`_orm.Session.execute` method, as well as related methods such as
:meth:`_orm.Session.scalars` and :meth:`_orm.Session.scalar`. As of
SQLAlchemy 1.4, all ORM queries that run through the
:meth:`_orm.Session.execute` method as well as related methods
:meth:`_orm.Session.scalars`, :meth:`_orm.Session.scalar` etc.
will participate in this event.
This event hook does **not** apply to the queries that are
emitted internally within the ORM flush process, i.e. the
process described at :ref:`session_flushing`.

.. note::  The :meth:`_orm.SessionEvents.do_orm_execute` event hook
   is triggered **for ORM statement executions only**, meaning those
   invoked via the :meth:`_orm.Session.execute` and similar methods on
   the :class:`_orm.Session` object. It does **not** trigger for
   statements that are invoked by SQLAlchemy Core only, i.e. statements
   invoked directly using :meth:`_engine.Connection.execute` or
   otherwise originating from an :class:`_engine.Engine` object without
   any :class:`_orm.Session` involved. To intercept **all** SQL
   executions regardless of whether the Core or ORM APIs are in use,
   see the event hooks at :class:`.ConnectionEvents`, such as
   :meth:`.ConnectionEvents.before_execute` and
   :meth:`.ConnectionEvents.before_cursor_execute`.

   Also, this event hook does **not** apply to queries that are
   emitted internally within the ORM flush process,
   i.e. the process described at :ref:`session_flushing`; to
   intercept steps within the flush process, see the event
   hooks described at :ref:`session_persistence_events` as
   well as :ref:`session_persistence_mapper`.

This event is a ``do_`` event, meaning it has the capability to replace
the operation that the :meth:`_orm.Session.execute` method normally
performs.  The intended use for this includes sharding and
result-caching schemes which may seek to invoke the same statement
across  multiple database connections, returning a result that is
merged from each of them, or which don't invoke the statement at all,
instead returning data from a cache.

The hook intends to replace the use of the
``Query._execute_and_instances`` method that could be subclassed prior
to SQLAlchemy 1.4.

:param orm_execute_state: an instance of :class:`.ORMExecuteState`
 which contains all information about the current execution, as well
 as helper functions used to derive other commonly required
 information.   See that object for details.

.. seealso::

    :ref:`session_execute_events` - top level documentation on how
    to use :meth:`_orm.SessionEvents.do_orm_execute`

    :class:`.ORMExecuteState` - the object passed to the
    :meth:`_orm.SessionEvents.do_orm_execute` event which contains
    all information about the statement to be invoked.  It also
    provides an interface to extend the current statement, options,
    and parameters as well as an option that allows programmatic
    invocation of the statement at any point.

    :ref:`examples_session_orm_events` - includes examples of using
    :meth:`_orm.SessionEvents.do_orm_execute`

    :ref:`examples_caching` - an example of how to integrate
    Dogpile caching with the ORM :class:`_orm.Session` making use
    of the :meth:`_orm.SessionEvents.do_orm_execute` event hook.

    :ref:`examples_sharding` - the Horizontal Sharding example /
    extension relies upon the
    :meth:`_orm.SessionEvents.do_orm_execute` event hook to invoke a
    SQL statement on multiple backends and return a merged result.


.. versionadded:: 1.4

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