PublicArchive/sqlalchemy
2
0
Fork 0
mirror of https://github.com/sqlalchemy/sqlalchemy.git synced 2026-05-11 03:10:38 -04:00
Code Issues Packages Projects Releases Wiki Activity

- event documentation bonanza

Browse Source
This commit is contained in:
Mike Bayer
2010-11-14 15:54:37 -05:00
parent 7513b46730
commit 80d1aaa661
8 changed files with 523 additions and 209 deletions
Download Patch File Download Diff File Expand all files Collapse all files
doc/build/core/event.rst
Vendored
+21 -4
View File
@@ -8,8 +8,6 @@ the internals of both SQLAlchemy Core and ORM. The system is all new
as of version 0.7 and supercedes the previous system of "extension", "proxy",
and "listener" classes.
Core events are described in :ref:`core_event_toplevel` and ORM events in :ref:`orm_event_toplevel`.
Event Registration
------------------
@@ -21,7 +19,7 @@ instructions regarding secondary event targets based on the given target.
The name of an event and the argument signature of a corresponding listener function is derived from
a class bound specification method, which exists bound to a marker class that's described in the documentation.
For example, the documentation for :ref:`.PoolEvents.on_connect` indicates that the event name is ``"on_connect"``
For example, the documentation for :meth:`.PoolEvents.on_connect` indicates that the event name is ``"on_connect"``
and that a user-defined listener function should receive two positional arguments::
from sqlalchemy.event import listen
@@ -82,6 +80,25 @@ which modifies the subsequent handling. By default, no listener ever requires
# it to use the return value
listen(validate_phone, 'on_set', UserContact.phone, retval=True)
Event Reference
----------------
Both SQLAlchemy Core and SQLAlchemy ORM feature a wide variety of event hooks:
* **Core Events** - these are described in
:ref:`core_event_toplevel` and include event hooks specific to
connection pool lifecycle, SQL statement execution,
transaction lifecycle, and schema creation and teardown.
* **ORM Events** - these are described in
:ref:`orm_event_toplevel`, and include event hooks specific to
class and attribute instrumentation, object initialization
hooks, attribute on-change hooks, session state, flush, and
commit hooks, mapper initialization, object/result population,
and per-instance persistence hooks.
API Reference
-------------
.. autofunction:: sqlalchemy.event.listen
doc/build/core/events.rst
Vendored
+6 -2
View File
@@ -3,8 +3,12 @@
Core Events
============
This section describes the event interfaces provided in SQLAlchemy Core. For an introduction
to the event listening API, see :ref:`event_toplevel`. ORM events are described in :ref:`orm_event_toplevel`.
This section describes the event interfaces provided in
SQLAlchemy Core. The event system in 0.7 is all new and
supercedes the previous system of "extension", "listener", and
"proxy" classes. For an introduction to the event listening API,
see :ref:`event_toplevel`. ORM events are described in
:ref:`orm_event_toplevel`.
Connection Pool Events
-----------------------
doc/build/orm/events.rst
Vendored
+17 -7
View File
@@ -5,7 +5,9 @@ ORM Events
The ORM includes a wide variety of hooks available for subscription. The event
system in 0.7 is all new and supercedes the previous system of "extension" classes.
For an introduction to the event API, see :ref:`core_event_toplevel`.
For an introduction to the event API, see :ref:`event_toplevel`. Non-ORM events
such as those regarding connections and low-level statement execution are described in
:ref:`core_event_toplevel`.
Attribute Events
----------------
@@ -13,12 +15,6 @@ Attribute Events
.. autoclass:: sqlalchemy.orm.events.AttributeEvents
:members:
Instrumentation Events
-----------------------
.. autoclass:: sqlalchemy.orm.events.InstrumentationEvents
:members:
Mapper Events
---------------
@@ -36,3 +32,17 @@ Session Events
TODO
Instrumentation Events
-----------------------
.. autoclass:: sqlalchemy.orm.events.InstrumentationEvents
:members:
Alternate Class Instrumentation
-------------------------------
.. autoclass:: sqlalchemy.orm.interfaces.InstrumentationManager
:members:
:undoc-members:
doc/build/orm/interfaces.rst
Vendored
-73
View File
@@ -16,91 +16,18 @@ a consistent interface to all events without the need for subclassing.
Mapper Events
-----------------
To use :class:`.MapperExtension`, make your own subclass of it and just send it off to a mapper::
from sqlalchemy.orm.interfaces import MapperExtension
class MyExtension(MapperExtension):
def before_insert(self, mapper, connection, instance):
print "instance %s before insert !" % instance
m = mapper(User, users_table, extension=MyExtension())
Multiple extensions will be chained together and processed in order; they are specified as a list::
m = mapper(User, users_table, extension=[ext1, ext2, ext3])
.. autoclass:: MapperExtension
:members:
Session Events
-----------------
The :class:`.SessionExtension` applies plugin points for :class:`.Session` objects::
from sqlalchemy.orm.interfaces import SessionExtension
class MySessionExtension(SessionExtension):
def before_commit(self, session):
print "before commit!"
Session = sessionmaker(extension=MySessionExtension())
The same :class:`~sqlalchemy.orm.interfaces.SessionExtension` instance can be
used with any number of sessions.
.. autoclass:: SessionExtension
:members:
Attribute Events
--------------------
:class:`.AttributeExtension` is used to listen for set, remove, and append
events on individual mapped attributes. It is established on an individual
mapped attribute using the `extension` argument, available on
:func:`.column_property`, :func:`.relationship`, and others::
from sqlalchemy.orm.interfaces import AttributeExtension
from sqlalchemy.orm import mapper, relationship, column_property
class MyAttrExt(AttributeExtension):
def append(self, state, value, initiator):
print "append event !"
return value
def set(self, state, value, oldvalue, initiator):
print "set event !"
return value
mapper(SomeClass, sometable, properties={
'foo':column_property(sometable.c.foo, extension=MyAttrExt()),
'bar':relationship(Bar, extension=MyAttrExt())
})
Note that the :class:`AttributeExtension` methods
:meth:`~.AttributeExtension.append` and :meth:`~.AttributeExtension.set` need
to return the ``value`` parameter. The returned value is used as the effective
value, and allows the extension to change what is ultimately persisted.
.. autoclass:: AttributeExtension
:members:
Instrumentation Events and Re-implementation
---------------------------------------------
:class:`.InstrumentationManager` can be subclassed in order to receive class
instrumentation events as well as to change how class instrumentation
proceeds. This class exists for the purposes of integration with other object
management frameworks which would like to entirely modify the instrumentation
methodology of the ORM, and is not intended for regular usage. One possible
exception is the :meth:`.InstrumentationManager.post_configure_attribute`
method, which can be useful for adding extensions to all mapped attributes,
though a much better way to do this will be available in a future release of
SQLAlchemy.
For an example of :class:`.InstrumentationManager`, see the example
:ref:`examples_instrumentation`.
.. autoclass:: InstrumentationManager
:members:
:undoc-members:
lib/sqlalchemy/events.py
+52 -4
View File
@@ -52,16 +52,64 @@ class DDLEvents(event.Events):
"""
def on_before_create(self, target, connection, **kw):
""" """
"""Called before CREATE statments are emitted.
:param target: the :class:`.MetaData` or :class:`.Table`
object which is the target of the event.
:param connection: the :class:`.Connection` where the
CREATE statement or statements will be emitted.
:param \**kw: additional keyword arguments relevant
to the event. Currently this includes the ``tables``
argument in the case of a :class:`.MetaData` object,
which is the list of :class:`.Table` objects for which
CREATE will be emitted.
"""
def on_after_create(self, target, connection, **kw):
""" """
"""Called after CREATE statments are emitted.
:param target: the :class:`.MetaData` or :class:`.Table`
object which is the target of the event.
:param connection: the :class:`.Connection` where the
CREATE statement or statements have been emitted.
:param \**kw: additional keyword arguments relevant
to the event. Currently this includes the ``tables``
argument in the case of a :class:`.MetaData` object,
which is the list of :class:`.Table` objects for which
CREATE has been emitted.
"""
def on_before_drop(self, target, connection, **kw):
""" """
"""Called before DROP statments are emitted.
:param target: the :class:`.MetaData` or :class:`.Table`
object which is the target of the event.
:param connection: the :class:`.Connection` where the
DROP statement or statements will be emitted.
:param \**kw: additional keyword arguments relevant
to the event. Currently this includes the ``tables``
argument in the case of a :class:`.MetaData` object,
which is the list of :class:`.Table` objects for which
DROP will be emitted.
"""
def on_after_drop(self, target, connection, **kw):
""" """
"""Called after DROP statments are emitted.
:param target: the :class:`.MetaData` or :class:`.Table`
object which is the target of the event.
:param connection: the :class:`.Connection` where the
DROP statement or statements have been emitted.
:param \**kw: additional keyword arguments relevant
to the event. Currently this includes the ``tables``
argument in the case of a :class:`.MetaData` object,
which is the list of :class:`.Table` objects for which
DROP has been emitted.
"""
class PoolEvents(event.Events):
lib/sqlalchemy/orm/deprecated_interfaces.py
+81 -14
View File
@@ -3,15 +3,31 @@ from interfaces import EXT_CONTINUE
class MapperExtension(object):
"""Base implementation for customizing ``Mapper`` behavior.
"""Base implementation for :class:`.Mapper` event hooks.
.. note:: :class:`.MapperExtension` is deprecated. Please
refer to :func:`.event.listen` as well as
:class:`.MapperEvents`.
New extension classes subclass ``MapperExtension`` and are specified
New extension classes subclass :class:`.MapperExtension` and are specified
using the ``extension`` mapper() argument, which is a single
``MapperExtension`` or a list of such. A single mapper
can maintain a chain of ``MapperExtension`` objects. When a
particular mapping event occurs, the corresponding method
on each ``MapperExtension`` is invoked serially, and each method
has the ability to halt the chain from proceeding further.
:class:`.MapperExtension` or a list of such::
from sqlalchemy.orm.interfaces import MapperExtension
class MyExtension(MapperExtension):
def before_insert(self, mapper, connection, instance):
print "instance %s before insert !" % instance
m = mapper(User, users_table, extension=MyExtension())
A single mapper can maintain a chain of ``MapperExtension``
objects. When a particular mapping event occurs, the
corresponding method on each ``MapperExtension`` is invoked
serially, and each method has the ability to halt the chain
from proceeding further::
m = mapper(User, users_table, extension=[ext1, ext2, ext3])
Each ``MapperExtension`` method returns the symbol
EXT_CONTINUE by default. This symbol generally means "move
@@ -354,9 +370,28 @@ class MapperExtension(object):
class SessionExtension(object):
"""An extension hook object for Sessions. Subclasses may be
installed into a Session (or sessionmaker) using the ``extension``
keyword argument. """
"""Base implementation for :class:`.Session` event hooks.
.. note:: :class:`.SessionExtension` is deprecated. Please
refer to :func:`.event.listen` as well as
:class:`.SessionEvents`.
Subclasses may be installed into a :class:`.Session` (or
:func:`.sessionmaker`) using the ``extension`` keyword
argument::
from sqlalchemy.orm.interfaces import SessionExtension
class MySessionExtension(SessionExtension):
def before_commit(self, session):
print "before commit!"
Session = sessionmaker(extension=MySessionExtension())
The same :class:`.SessionExtension` instance can be used
with any number of sessions.
"""
def before_commit(self, session):
"""Execute right before commit is called.
@@ -432,11 +467,43 @@ class SessionExtension(object):
class AttributeExtension(object):
"""An event handler for individual attribute change events.
"""Base implementation for :class:`.AttributeImpl` event hooks, events
that fire upon attribute mutations in user code.
.. note:: :class:`.AttributeExtension` is deprecated. Please
refer to :func:`.event.listen` as well as
:class:`.AttributeEvents`.
.. note:: :class:`AttributeExtension` is deprecated. Please
refer to :func:`event.listen` as well as
:attr:`AttributeImpl.events`.
:class:`.AttributeExtension` is used to listen for set,
remove, and append events on individual mapped attributes.
It is established on an individual mapped attribute using
the `extension` argument, available on
:func:`.column_property`, :func:`.relationship`, and
others::
from sqlalchemy.orm.interfaces import AttributeExtension
from sqlalchemy.orm import mapper, relationship, column_property
class MyAttrExt(AttributeExtension):
def append(self, state, value, initiator):
print "append event !"
return value
def set(self, state, value, oldvalue, initiator):
print "set event !"
return value
mapper(SomeClass, sometable, properties={
'foo':column_property(sometable.c.foo, extension=MyAttrExt()),
'bar':relationship(Bar, extension=MyAttrExt())
})
Note that the :class:`AttributeExtension` methods
:meth:`~.AttributeExtension.append` and
:meth:`~.AttributeExtension.set` need to return the
``value`` parameter. The returned value is used as the
effective value, and allows the extension to change what is
ultimately persisted.
AttributeExtension is assembled within the descriptors associated
with a mapped class.
lib/sqlalchemy/orm/events.py
+334 -105
View File
@@ -133,45 +133,79 @@ class InstanceEvents(event.Events):
"""
def on_resurrect(self, target):
""""""
"""Receive an object instance as it is 'resurrected' from
garbage collection, which occurs when a "dirty" state falls
out of scope."""
class MapperEvents(event.Events):
"""Define events specific to mappings.
e.g.::
from sqlalchemy import event
from sqlalchemy.orm import mapper
# attach to a class
def my_before_insert_listener(mapper, connection, target):
# execute a stored procedure upon INSERT,
# apply the value to the row to be inserted
target.calculated_value = connection.scalar(
"select my_special_function(%d)"
% target.special_number)
# associate the listener function with SomeMappedClass,
# to execute during the "on_before_insert" hook
event.listen(my_before_insert_listener, 'on_before_insert', SomeMappedClass)
Available targets include mapped classes, instances of
:class:`.Mapper` (i.e. returned by :func:`.mapper`,
:func:`.class_mapper` and similar), as well as the
:class:`.Mapper` class and :func:`.mapper` function itself
for global event reception::
from sqlalchemy.orm import mapper
def some_listener(mapper, connection, target):
log.debug("Instance %s being inserted" % target)
# attach to all mappers
event.listen(some_listener, 'on_before_insert', mapper)
Mapper event listeners are propagated to subclass (inheriting)
mappers unconditionally.
Mapper events provide hooks into critical sections of the
mapper, including those related to object instrumentation,
object loading, and object persistence. In particular, the
persistence methods :meth:`~.MapperEvents.on_before_insert`,
and :meth:`~.MapperEvents.on_before_update` are popular
places to augment the state being persisted - however, these
methods operate with several significant restrictions. The
user is encouraged to evaluate the
:meth:`.SessionEvents.on_before_flush` and
:meth:`.SessionEvents.on_after_flush` methods as more
flexible and user-friendly hooks in which to apply
additional database state during a flush.
Several modifiers are available to the listen() function.
When using :class:`.MapperEvents`, several modifiers are
available to the :func:`.event.listen` function.
:param propagate=False: When True, the event listener should
be applied to all inheriting mappers as well.
:param raw=False: When True, the "target" argument to the
event, if applicable will be the :class:`.InstanceState` management
be applied to all inheriting mappers as well as the
mapper which is the target of this listener.
:param raw=False: When True, the "target" argument passed
to applicable event listener functions will be the
instance's :class:`.InstanceState` management
object, rather than the mapped instance itself.
:param retval=False: when True, the user-defined event function
must have a return value, the purpose of which is either to
control subsequent event propagation, or to otherwise alter
the operation in progress by the mapper. Possible values
here are:
the operation in progress by the mapper. Possible return
values are:
* ``sqlalchemy.orm.interfaces.EXT_CONTINUE`` - continue event
processing normally.
* ``sqlalchemy.orm.interfaces.EXT_STOP`` - cancel all subsequent
event handlers in the chain.
* other values - the return value specified by specific listeners,
such as "translate_row" or "create_instance".
such as :meth:`~.MapperEvents.on_translate_row` or
:meth:`~.MapperEvents.on_create_instance`.
"""
@@ -226,6 +260,10 @@ class MapperEvents(event.Events):
This listener can generally only be applied to the :class:`.Mapper`
class overall.
:param mapper: the :class:`.Mapper` which is the target
of this event.
:param class\_: the mapped class.
"""
def on_translate_row(self, mapper, context, row):
@@ -236,13 +274,23 @@ class MapperEvents(event.Events):
It is called when the mapper first receives a row, before
the object identity or the instance itself has been derived
from that row. The given row may or may not be a
``RowProxy`` object - it will always be a dictionary-like
:class:`.RowProxy` object - it will always be a dictionary-like
object which contains mapped columns as keys. The
returned object should also be a dictionary-like object
which recognizes mapped columns as keys.
If the ultimate return value is EXT_CONTINUE, the row
is not translated.
:param mapper: the :class:`.Mapper` which is the target
of this event.
:param context: the :class:`.QueryContext`, which includes
a handle to the current :class:`.Query` in progress as well
as additional state information.
:param row: the result row being handled. This may be
an actual :class:`.RowProxy` or may be a dictionary containing
:class:`.Column` objects as keys.
:return: When configured with ``retval=True``, the function
should return a dictionary-like row object, or ``EXT_CONTINUE``,
indicating the original row should be used.
"""
@@ -254,20 +302,19 @@ class MapperEvents(event.Events):
EXT_CONTINUE to indicate normal object creation should take place.
This listener is typically registered with ``retval=True``.
mapper
The mapper doing the operation
context
The QueryContext generated from the Query.
row
The result row from the database
class\_
The class we are mapping.
return value
A new object instance, or EXT_CONTINUE
:param mapper: the :class:`.Mapper` which is the target
of this event.
:param context: the :class:`.QueryContext`, which includes
a handle to the current :class:`.Query` in progress as well
as additional state information.
:param row: the result row being handled. This may be
an actual :class:`.RowProxy` or may be a dictionary containing
:class:`.Column` objects as keys.
:param class\_: the mapped class.
:return: When configured with ``retval=True``, the return value
should be a newly created instance of the mapped class,
or ``EXT_CONTINUE`` indicating that default object construction
should take place.
"""
@@ -275,33 +322,32 @@ class MapperEvents(event.Events):
result, **flags):
"""Receive an object instance before that instance is appended
to a result list.
This is a rarely used hook which can be used to alter
the construction of a result list returned by :class:`.Query`.
:param mapper: the :class:`.Mapper` which is the target
of this event.
:param context: the :class:`.QueryContext`, which includes
a handle to the current :class:`.Query` in progress as well
as additional state information.
:param row: the result row being handled. This may be
an actual :class:`.RowProxy` or may be a dictionary containing
:class:`.Column` objects as keys.
:param target: the mapped instance being populated. If
the event is configured with ``raw=True``, this will
instead be the :class:`.InstanceState` state-management
object associated with the instance.
:param result: a list-like object where results are being
appended.
:param \**flags: Additional state information about the
current handling of the row.
:return: If this method is registered with ``retval=True``,
a return value of ``EXT_STOP`` will prevent the instance
from being appended to the given result list, whereas a
return value of ``EXT_CONTINUE`` will result in the default
behavior of appending the value to the result list.
If this method is registered with ``retval=True``,
the append operation can be replaced. If any value other than
EXT_CONTINUE is returned, result appending will not proceed for
this instance, giving this extension an opportunity to do the
appending itself, if desired.
mapper
The mapper doing the operation.
selectcontext
The QueryContext generated from the Query.
row
The result row from the database.
target
The object instance to be appended to the result, or
the InstanceState if registered with ``raw=True``.
result
List to which results are being appended.
\**flags
extra information about the row, same as criterion in
``create_row_processor()`` method of
:class:`~sqlalchemy.orm.interfaces.MapperProperty`
"""
@@ -315,86 +361,265 @@ class MapperEvents(event.Events):
unloaded attributes to be populated. The method may be called
many times for a single instance, as multiple result rows are
used to populate eagerly loaded collections.
If this listener is registered with ``retval=True`` and
returns EXT_CONTINUE, instance population will
proceed normally. If any other value or None is returned,
instance population will not proceed, giving this extension an
opportunity to populate the instance itself, if desired.
As of 0.5, most usages of this hook are obsolete. For a
Most usages of this hook are obsolete. For a
generic "object has been newly created from a row" hook, use
``reconstruct_instance()``, or the ``@orm.reconstructor``
decorator.
:meth:`.InstanceEvents.on_load`.
:param mapper: the :class:`.Mapper` which is the target
of this event.
:param context: the :class:`.QueryContext`, which includes
a handle to the current :class:`.Query` in progress as well
as additional state information.
:param row: the result row being handled. This may be
an actual :class:`.RowProxy` or may be a dictionary containing
:class:`.Column` objects as keys.
:param class\_: the mapped class.
:return: When configured with ``retval=True``, a return
value of ``EXT_STOP`` will bypass instance population by
the mapper. A value of ``EXT_CONTINUE`` indicates that
default instance population should take place.
"""
def on_before_insert(self, mapper, connection, target):
"""Receive an object instance before that instance is inserted
into its table.
"""Receive an object instance before an INSERT statement
is emitted corresponding to that instance.
This event is used to modify local, non-object related
attributes on the instance before an INSERT occurs, as well
as to emit additional SQL statements on the given
connection.
The event is often called for a batch of objects of the
same class before their INSERT statements are emitted at
once in a later step. In the extremely rare case that
this is not desirable, the :func:`.mapper` can be
configured with ``batch=False``, which will cause
batches of instances to be broken up into individual
(and more poorly performing) event->persist->event
steps.
Handlers should **not** modify any attributes which are
mapped by :func:`.relationship`, nor should they attempt
to make any modifications to the :class:`.Session` in
this hook (including :meth:`.Session.add`,
:meth:`.Session.delete`, etc.) - such changes will not
take effect. For overall changes to the "flush plan",
use :meth:`.SessionEvents.before_flush`.
This is a good place to set up primary key values and such
that aren't handled otherwise.
Column-based attributes can be modified within this method
which will result in the new value being inserted. However
*no* changes to the overall flush plan can be made, and
manipulation of the ``Session`` will not have the desired effect.
To manipulate the ``Session`` within an extension, use
``SessionExtension``.
:param mapper: the :class:`.Mapper` which is the target
of this event.
:param connection: the :class:`.Connection` being used to
emit INSERT statements for this instance. This
provides a handle into the current transaction on the
target database specific to this instance.
:param target: the mapped instance being persisted. If
the event is configured with ``raw=True``, this will
instead be the :class:`.InstanceState` state-management
object associated with the instance.
:return: No return value is supported by this event.
"""
def on_after_insert(self, mapper, connection, target):
"""Receive an object instance after that instance is inserted.
"""Receive an object instance after an INSERT statement
is emitted corresponding to that instance.
This event is used to modify in-Python-only
state on the instance after an INSERT occurs, as well
as to emit additional SQL statements on the given
connection.
The event is often called for a batch of objects of the
same class after their INSERT statements have been
emitted at once in a previous step. In the extremely
rare case that this is not desirable, the
:func:`.mapper` can be configured with ``batch=False``,
which will cause batches of instances to be broken up
into individual (and more poorly performing)
event->persist->event steps.
:param mapper: the :class:`.Mapper` which is the target
of this event.
:param connection: the :class:`.Connection` being used to
emit INSERT statements for this instance. This
provides a handle into the current transaction on the
target database specific to this instance.
:param target: the mapped instance being persisted. If
the event is configured with ``raw=True``, this will
instead be the :class:`.InstanceState` state-management
object associated with the instance.
:return: No return value is supported by this event.
"""
def on_before_update(self, mapper, connection, target):
"""Receive an object instance before that instance is updated.
"""Receive an object instance before an UPDATE statement
is emitted corresponding to that instance.
Note that this method is called for all instances that are marked as
"dirty", even those which have no net changes to their column-based
attributes. An object is marked as dirty when any of its column-based
attributes have a "set attribute" operation called or when any of its
collections are modified. If, at update time, no column-based
attributes have any net changes, no UPDATE statement will be issued.
This means that an instance being sent to before_update is *not* a
guarantee that an UPDATE statement will be issued (although you can
affect the outcome here).
This event is used to modify local, non-object related
attributes on the instance before an UPDATE occurs, as well
as to emit additional SQL statements on the given
connection.
This method is called for all instances that are
marked as "dirty", *even those which have no net changes
to their column-based attributes*. An object is marked
as dirty when any of its column-based attributes have a
"set attribute" operation called or when any of its
collections are modified. If, at update time, no
column-based attributes have any net changes, no UPDATE
statement will be issued. This means that an instance
being sent to :meth:`~.MapperEvents.on_before_update` is
*not* a guarantee that an UPDATE statement will be
issued, although you can affect the outcome here by
modifying attributes so that a net change in value does
exist.
To detect if the column-based attributes on the object have net
changes, and will therefore generate an UPDATE statement, use
``object_session(instance).is_modified(instance,
include_collections=False)``.
Column-based attributes can be modified within this method
which will result in the new value being updated. However
*no* changes to the overall flush plan can be made, and
manipulation of the ``Session`` will not have the desired effect.
To manipulate the ``Session`` within an extension, use
``SessionExtension``.
The event is often called for a batch of objects of the
same class before their UPDATE statements are emitted at
once in a later step. In the extremely rare case that
this is not desirable, the :func:`.mapper` can be
configured with ``batch=False``, which will cause
batches of instances to be broken up into individual
(and more poorly performing) event->persist->event
steps.
Handlers should **not** modify any attributes which are
mapped by :func:`.relationship`, nor should they attempt
to make any modifications to the :class:`.Session` in
this hook (including :meth:`.Session.add`,
:meth:`.Session.delete`, etc.) - such changes will not
take effect. For overall changes to the "flush plan",
use :meth:`.SessionEvents.before_flush`.
:param mapper: the :class:`.Mapper` which is the target
of this event.
:param connection: the :class:`.Connection` being used to
emit UPDATE statements for this instance. This
provides a handle into the current transaction on the
target database specific to this instance.
:param target: the mapped instance being persisted. If
the event is configured with ``raw=True``, this will
instead be the :class:`.InstanceState` state-management
object associated with the instance.
:return: No return value is supported by this event.
"""
def on_after_update(self, mapper, connection, target):
"""Receive an object instance after that instance is updated.
"""Receive an object instance after an UPDATE statement
is emitted corresponding to that instance.
This event is used to modify in-Python-only
state on the instance after an UPDATE occurs, as well
as to emit additional SQL statements on the given
connection.
This method is called for all instances that are
marked as "dirty", *even those which have no net changes
to their column-based attributes*, and for which
no UPDATE statement has proceeded. An object is marked
as dirty when any of its column-based attributes have a
"set attribute" operation called or when any of its
collections are modified. If, at update time, no
column-based attributes have any net changes, no UPDATE
statement will be issued. This means that an instance
being sent to :meth:`~.MapperEvents.on_after_update` is
*not* a guarantee that an UPDATE statement has been
issued.
To detect if the column-based attributes on the object have net
changes, and therefore resulted in an UPDATE statement, use
``object_session(instance).is_modified(instance,
include_collections=False)``.
The event is often called for a batch of objects of the
same class after their UPDATE statements have been emitted at
once in a previous step. In the extremely rare case that
this is not desirable, the :func:`.mapper` can be
configured with ``batch=False``, which will cause
batches of instances to be broken up into individual
(and more poorly performing) event->persist->event
steps.
:param mapper: the :class:`.Mapper` which is the target
of this event.
:param connection: the :class:`.Connection` being used to
emit UPDATE statements for this instance. This
provides a handle into the current transaction on the
target database specific to this instance.
:param target: the mapped instance being persisted. If
the event is configured with ``raw=True``, this will
instead be the :class:`.InstanceState` state-management
object associated with the instance.
:return: No return value is supported by this event.
"""
def on_before_delete(self, mapper, connection, target):
"""Receive an object instance before that instance is deleted.
Note that *no* changes to the overall flush plan can be made
here; and manipulation of the ``Session`` will not have the
desired effect. To manipulate the ``Session`` within an
extension, use ``SessionExtension``.
"""Receive an object instance before a DELETE statement
is emitted corresponding to that instance.
This event is used to emit additional SQL statements on
the given connection as well as to perform application
specific bookkeeping related to a deletion event.
The event is often called for a batch of objects of the
same class before their DELETE statements are emitted at
once in a later step.
Handlers should **not** modify any attributes which are
mapped by :func:`.relationship`, nor should they attempt
to make any modifications to the :class:`.Session` in
this hook (including :meth:`.Session.add`,
:meth:`.Session.delete`, etc.) - such changes will not
take effect. For overall changes to the "flush plan",
use :meth:`.SessionEvents.before_flush`.
:param mapper: the :class:`.Mapper` which is the target
of this event.
:param connection: the :class:`.Connection` being used to
emit DELETE statements for this instance. This
provides a handle into the current transaction on the
target database specific to this instance.
:param target: the mapped instance being deleted. If
the event is configured with ``raw=True``, this will
instead be the :class:`.InstanceState` state-management
object associated with the instance.
:return: No return value is supported by this event.
"""
def on_after_delete(self, mapper, connection, target):
"""Receive an object instance after that instance is deleted.
"""Receive an object instance after a DELETE statement
has been emitted corresponding to that instance.
This event is used to emit additional SQL statements on
the given connection as well as to perform application
specific bookkeeping related to a deletion event.
The event is often called for a batch of objects of the
same class after their DELETE statements have been emitted at
once in a previous step.
:param mapper: the :class:`.Mapper` which is the target
of this event.
:param connection: the :class:`.Connection` being used to
emit DELETE statements for this instance. This
provides a handle into the current transaction on the
target database specific to this instance.
:param target: the mapped instance being deleted. If
the event is configured with ``raw=True``, this will
instead be the :class:`.InstanceState` state-management
object associated with the instance.
:return: No return value is supported by this event.
"""
@classmethod
@@ -417,7 +642,7 @@ class AttributeEvents(event.Events):
event.listen(my_set_listener, 'on_set',
MyClass.somescalar, retval=True)
Several modifiers are available to the listen() function.
Several modifiers are available to the :func:`~event.listen` function.
:param active_history=False: When True, indicates that the
"on_set" event would like to receive the "old" value
@@ -488,7 +713,9 @@ class AttributeEvents(event.Events):
replaces it.
:param initiator: the attribute implementation object
which initiated this event.
:return: if the event was registered with ``retval=True``,
the given value, or a new effective value, should be returned.
"""
def on_remove(self, target, value, initiator):
@@ -500,7 +727,7 @@ class AttributeEvents(event.Events):
:param value: the value being removed.
:param initiator: the attribute implementation object
which initiated this event.
:return: No return value is defined for this event.
"""
def on_set(self, target, value, oldvalue, initiator):
@@ -521,6 +748,8 @@ class AttributeEvents(event.Events):
or expired.
:param initiator: the attribute implementation object
which initiated this event.
:return: if the event was registered with ``retval=True``,
the given value, or a new effective value, should be returned.
"""
lib/sqlalchemy/orm/interfaces.py
+12
View File
@@ -616,6 +616,18 @@ class LoaderStrategy(object):
class InstrumentationManager(object):
"""User-defined class instrumentation extension.
:class:`.InstrumentationManager` can be subclassed in order
to change
how class instrumentation proceeds. This class exists for
the purposes of integration with other object management
frameworks which would like to entirely modify the
instrumentation methodology of the ORM, and is not intended
for regular usage. For interception of class instrumentation
events, see :class:`.InstrumentationEvents`.
For an example of :class:`.InstrumentationManager`, see the
example :ref:`examples_instrumentation`.
The API for this class should be considered as semi-stable,
and may change slightly with new releases.