# attributes.py - manages object attributes
# Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010 Michael Bayer mike_mp@zzzcomputing.com
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
"""Defines SQLAlchemy's system of class instrumentation..
This module is usually not directly visible to user applications, but
defines a large part of the ORM's interactivity.
SQLA's instrumentation system is completely customizable, in which
case an understanding of the general mechanics of this module is helpful.
An example of full customization is in /examples/custom_attributes.
"""
import operator
from operator import attrgetter,itemgetter
import types
import weakref
from sqlalchemy import util
from sqlalchemy.orm import interfaces,collections,exc
import sqlalchemy.exceptions as sa_exc
# lazy imports
_entity_info = None
identity_equal = None
state = None
PASSIVE_NO_RESULT = util.symbol('PASSIVE_NO_RESULT')
ATTR_WAS_SET = util.symbol('ATTR_WAS_SET')
NO_VALUE = util.symbol('NO_VALUE')
NEVER_SET = util.symbol('NEVER_SET')
# "passive" get settings
# TODO: the True/False values need to be factored out
# of the rest of ORM code
# don't fire off any callables, and don't initialize the attribute to
# an empty value
PASSIVE_NO_INITIALIZE = True #util.symbol('PASSIVE_NO_INITIALIZE')
# don't fire off any callables, but if no callables present
# then initialize to an empty value/collection
# this is used by backrefs.
PASSIVE_NO_FETCH = util.symbol('PASSIVE_NO_FETCH')
# fire callables/initialize as needed
PASSIVE_OFF = False #util.symbol('PASSIVE_OFF')
INSTRUMENTATION_MANAGER = '__sa_instrumentation_manager__'
"""Attribute, elects custom instrumentation when present on a mapped class.
Allows a class to specify a slightly or wildly different technique for
tracking changes made to mapped attributes and collections.
Only one instrumentation implementation is allowed in a given object
inheritance hierarchy.
The value of this attribute must be a callable and will be passed a class
object. The callable must return one of:
- An instance of an interfaces.InstrumentationManager or subclass
- An object implementing all or some of InstrumentationManager (TODO)
- A dictionary of callables, implementing all or some of the above (TODO)
- An instance of a ClassManager or subclass
interfaces.InstrumentationManager is public API and will remain stable
between releases. ClassManager is not public and no guarantees are made
about stability. Caveat emptor.
This attribute is consulted by the default SQLAlchemy instrumentation
resolution code. If custom finders are installed in the global
instrumentation_finders list, they may or may not choose to honor this
attribute.
"""
instrumentation_finders = []
"""An extensible sequence of instrumentation implementation finding callables.
Finders callables will be passed a class object. If None is returned, the
next finder in the sequence is consulted. Otherwise the return must be an
instrumentation factory that follows the same guidelines as
INSTRUMENTATION_MANAGER.
By default, the only finder is find_native_user_instrumentation_hook, which
searches for INSTRUMENTATION_MANAGER. If all finders return None, standard
ClassManager instrumentation is used.
"""
class QueryableAttribute(interfaces.PropComparator):
def __init__(self, key, impl=None, comparator=None, parententity=None):
"""Construct an InstrumentedAttribute.
comparator
a sql.Comparator to which class-level compare/math events will be sent
"""
self.key = key
self.impl = impl
self.comparator = comparator
self.parententity = parententity
def get_history(self, instance, **kwargs):
return self.impl.get_history(instance_state(instance), instance_dict(instance), **kwargs)
def __selectable__(self):
# TODO: conditionally attach this method based on clause_element ?
return self
def __clause_element__(self):
return self.comparator.__clause_element__()
def label(self, name):
return self.__clause_element__().label(name)
def operate(self, op, *other, **kwargs):
return op(self.comparator, *other, **kwargs)
def reverse_operate(self, op, other, **kwargs):
return op(other, self.comparator, **kwargs)
def hasparent(self, state, optimistic=False):
return self.impl.hasparent(state, optimistic=optimistic)
def __getattr__(self, key):
try:
return getattr(self.comparator, key)
except AttributeError:
raise AttributeError(
'Neither %r object nor %r object has an attribute %r' % (
type(self).__name__,
type(self.comparator).__name__,
key)
)
def __str__(self):
return repr(self.parententity) + "." + self.property.key
@property
def property(self):
return self.comparator.property
class InstrumentedAttribute(QueryableAttribute):
"""Public-facing descriptor, placed in the mapped class dictionary."""
def __set__(self, instance, value):
self.impl.set(instance_state(instance), instance_dict(instance), value, None)
def __delete__(self, instance):
self.impl.delete(instance_state(instance), instance_dict(instance))
def __get__(self, instance, owner):
if instance is None:
return self
return self.impl.get(instance_state(instance), instance_dict(instance))
class _ProxyImpl(object):
accepts_scalar_loader = False
expire_missing = True
def __init__(self, key):
self.key = key
def proxied_attribute_factory(descriptor):
"""Create an InstrumentedAttribute / user descriptor hybrid.
Returns a new InstrumentedAttribute type that delegates descriptor
behavior and getattr() to the given descriptor.
"""
class Proxy(InstrumentedAttribute):
"""A combination of InsturmentedAttribute and a regular descriptor."""
def __init__(self, key, descriptor, comparator, parententity):
self.key = key
# maintain ProxiedAttribute.user_prop compatability.
self.descriptor = self.user_prop = descriptor
self._comparator = comparator
self._parententity = parententity
self.impl = _ProxyImpl(key)
@util.memoized_property
def comparator(self):
if util.callable(self._comparator):
self._comparator = self._comparator()
return self._comparator
def __get__(self, instance, owner):
"""Delegate __get__ to the original descriptor."""
if instance is None:
descriptor.__get__(instance, owner)
return self
return descriptor.__get__(instance, owner)
def __set__(self, instance, value):
"""Delegate __set__ to the original descriptor."""
return descriptor.__set__(instance, value)
def __delete__(self, instance):
"""Delegate __delete__ to the original descriptor."""
return descriptor.__delete__(instance)
def __getattr__(self, attribute):
"""Delegate __getattr__ to the original descriptor and/or comparator."""
try:
return getattr(descriptor, attribute)
except AttributeError:
try:
return getattr(self._comparator, attribute)
except AttributeError:
raise AttributeError(
'Neither %r object nor %r object has an attribute %r' % (
type(descriptor).__name__,
type(self._comparator).__name__,
attribute)
)
Proxy.__name__ = type(descriptor).__name__ + 'Proxy'
util.monkeypatch_proxied_specials(Proxy, type(descriptor),
name='descriptor',
from_instance=descriptor)
return Proxy
class AttributeImpl(object):
"""internal implementation for instrumented attributes."""
def __init__(self, class_, key,
callable_, trackparent=False, extension=None,
compare_function=None, active_history=False,
parent_token=None, expire_missing=True,
**kwargs):
"""Construct an AttributeImpl.
\class_
associated class
key
string name of the attribute
\callable_
optional function which generates a callable based on a parent
instance, which produces the "default" values for a scalar or
collection attribute when it's first accessed, if not present
already.
trackparent
if True, attempt to track if an instance has a parent attached
to it via this attribute.
extension
a single or list of AttributeExtension object(s) which will
receive set/delete/append/remove/etc. events.
compare_function
a function that compares two values which are normally
assignable to this attribute.
active_history
indicates that get_history() should always return the "old" value,
even if it means executing a lazy callable upon attribute change.
parent_token
Usually references the MapperProperty, used as a key for
the hasparent() function to identify an "owning" attribute.
Allows multiple AttributeImpls to all match a single
owner attribute.
expire_missing
if False, don't add an "expiry" callable to this attribute
during state.expire_attributes(None), if no value is present
for this key.
"""
self.class_ = class_
self.key = key
self.callable_ = callable_
self.trackparent = trackparent
self.parent_token = parent_token or self
if compare_function is None:
self.is_equal = operator.eq
else:
self.is_equal = compare_function
self.extensions = util.to_list(extension or [])
for e in self.extensions:
if e.active_history:
active_history = True
break
self.active_history = active_history
self.expire_missing = expire_missing
def hasparent(self, state, optimistic=False):
"""Return the boolean value of a `hasparent` flag attached to
the given state.
The `optimistic` flag determines what the default return value
should be if no `hasparent` flag can be located.
As this function is used to determine if an instance is an
*orphan*, instances that were loaded from storage should be
assumed to not be orphans, until a True/False value for this
flag is set.
An instance attribute that is loaded by a callable function
will also not have a `hasparent` flag.
"""
return state.parents.get(id(self.parent_token), optimistic)
def sethasparent(self, state, value):
"""Set a boolean flag on the given item corresponding to
whether or not it is attached to a parent object via the
attribute represented by this ``InstrumentedAttribute``.
"""
state.parents[id(self.parent_token)] = value
def set_callable(self, state, callable_):
"""Set a callable function for this attribute on the given object.
This callable will be executed when the attribute is next
accessed, and is assumed to construct part of the instances
previously stored state. When its value or values are loaded,
they will be established as part of the instance's *committed
state*. While *trackparent* information will be assembled for
these instances, attribute-level event handlers will not be
fired.
The callable overrides the class level callable set in the
``InstrumentedAttribute`` constructor.
"""
state.callables[self.key] = callable_
def get_history(self, state, dict_, passive=PASSIVE_OFF):
raise NotImplementedError()
def _get_callable(self, state):
if self.key in state.callables:
return state.callables[self.key]
elif self.callable_ is not None:
return self.callable_(state)
else:
return None
def initialize(self, state, dict_):
"""Initialize the given state's attribute with an empty value."""
dict_[self.key] = None
return None
def get(self, state, dict_, passive=PASSIVE_OFF):
"""Retrieve a value from the given object.
If a callable is assembled on this object's attribute, and
passive is False, the callable will be executed and the
resulting value will be set as the new value for this attribute.
"""
try:
return dict_[self.key]
except KeyError:
# if no history, check for lazy callables, etc.
if state.committed_state.get(self.key, NEVER_SET) is NEVER_SET:
if passive is PASSIVE_NO_INITIALIZE:
return PASSIVE_NO_RESULT
callable_ = self._get_callable(state)
if callable_ is not None:
#if passive is not PASSIVE_OFF:
# return PASSIVE_NO_RESULT
value = callable_(passive=passive)
if value is PASSIVE_NO_RESULT:
return value
elif value is not ATTR_WAS_SET:
return self.set_committed_value(state, dict_, value)
else:
if self.key not in dict_:
return self.get(state, dict_, passive=passive)
return dict_[self.key]
# Return a new, empty value
return self.initialize(state, dict_)
def append(self, state, dict_, value, initiator, passive=PASSIVE_OFF):
self.set(state, dict_, value, initiator, passive=passive)
def remove(self, state, dict_, value, initiator, passive=PASSIVE_OFF):
self.set(state, dict_, None, initiator, passive=passive)
def set(self, state, dict_, value, initiator, passive=PASSIVE_OFF):
raise NotImplementedError()
def get_committed_value(self, state, dict_, passive=PASSIVE_OFF):
"""return the unchanged value of this attribute"""
if self.key in state.committed_state:
if state.committed_state[self.key] is NO_VALUE:
return None
else:
return state.committed_state.get(self.key)
else:
return self.get(state, dict_, passive=passive)
def set_committed_value(self, state, dict_, value):
"""set an attribute value on the given instance and 'commit' it."""
state.commit(dict_, [self.key])
state.callables.pop(self.key, None)
state.dict[self.key] = value
return value
class ScalarAttributeImpl(AttributeImpl):
"""represents a scalar value-holding InstrumentedAttribute."""
accepts_scalar_loader = True
uses_objects = False
def delete(self, state, dict_):
# TODO: catch key errors, convert to attributeerror?
if self.active_history:
old = self.get(state, dict_)
else:
old = dict_.get(self.key, NO_VALUE)
if self.extensions:
self.fire_remove_event(state, dict_, old, None)
state.modified_event(dict_, self, False, old)
del dict_[self.key]
def get_history(self, state, dict_, passive=PASSIVE_OFF):
return History.from_attribute(
self, state, dict_.get(self.key, NO_VALUE))
def set(self, state, dict_, value, initiator, passive=PASSIVE_OFF):
if initiator is self:
return
if self.active_history:
old = self.get(state, dict_)
else:
old = dict_.get(self.key, NO_VALUE)
if self.extensions:
value = self.fire_replace_event(state, dict_, value, old, initiator)
state.modified_event(dict_, self, False, old)
dict_[self.key] = value
def fire_replace_event(self, state, dict_, value, previous, initiator):
for ext in self.extensions:
value = ext.set(state, value, previous, initiator or self)
return value
def fire_remove_event(self, state, dict_, value, initiator):
for ext in self.extensions:
ext.remove(state, value, initiator or self)
@property
def type(self):
self.property.columns[0].type
class MutableScalarAttributeImpl(ScalarAttributeImpl):
"""represents a scalar value-holding InstrumentedAttribute, which can detect
changes within the value itself.
"""
uses_objects = False
def __init__(self, class_, key, callable_,
class_manager, copy_function=None,
compare_function=None, **kwargs):
super(ScalarAttributeImpl, self).__init__(
class_,
key,
callable_,
compare_function=compare_function,
**kwargs)
class_manager.mutable_attributes.add(key)
if copy_function is None:
raise sa_exc.ArgumentError(
"MutableScalarAttributeImpl requires a copy function")
self.copy = copy_function
def get_history(self, state, dict_, passive=PASSIVE_OFF):
if not dict_:
v = state.committed_state.get(self.key, NO_VALUE)
else:
v = dict_.get(self.key, NO_VALUE)
return History.from_attribute(
self, state, v)
def check_mutable_modified(self, state, dict_):
v = dict_.get(self.key, NO_VALUE)
a, u, d = History.from_attribute(self, state, v)
return bool(a or d)
def get(self, state, dict_, passive=PASSIVE_OFF):
if self.key not in state.mutable_dict:
ret = ScalarAttributeImpl.get(self, state, dict_, passive=passive)
if ret is not PASSIVE_NO_RESULT:
state.mutable_dict[self.key] = ret
return ret
else:
return state.mutable_dict[self.key]
def delete(self, state, dict_):
ScalarAttributeImpl.delete(self, state, dict_)
state.mutable_dict.pop(self.key)
def set(self, state, dict_, value, initiator, passive=PASSIVE_OFF):
if initiator is self:
return
if self.extensions:
old = self.get(state, dict_)
value = self.fire_replace_event(state, dict_, value, old, initiator)
state.modified_event(dict_, self, True, NEVER_SET)
dict_[self.key] = value
state.mutable_dict[self.key] = value
class ScalarObjectAttributeImpl(ScalarAttributeImpl):
"""represents a scalar-holding InstrumentedAttribute,
where the target object is also instrumented.
Adds events to delete/set operations.
"""
accepts_scalar_loader = False
uses_objects = True
def __init__(self, class_, key, callable_,
trackparent=False, extension=None, copy_function=None,
compare_function=None, **kwargs):
super(ScalarObjectAttributeImpl, self).__init__(
class_,
key,
callable_,
trackparent=trackparent,
extension=extension,
compare_function=compare_function,
**kwargs)
if compare_function is None:
self.is_equal = identity_equal
def delete(self, state, dict_):
old = self.get(state, dict_)
self.fire_remove_event(state, dict_, old, self)
del dict_[self.key]
def get_history(self, state, dict_, passive=PASSIVE_OFF):
if self.key in dict_:
return History.from_attribute(self, state, dict_[self.key])
else:
current = self.get(state, dict_, passive=passive)
if current is PASSIVE_NO_RESULT:
return HISTORY_BLANK
else:
return History.from_attribute(self, state, current)
def set(self, state, dict_, value, initiator, passive=PASSIVE_OFF):
"""Set a value on the given InstanceState.
`initiator` is the ``InstrumentedAttribute`` that initiated the
``set()`` operation and is used to control the depth of a circular
setter operation.
"""
if initiator is self:
return
if self.active_history:
old = self.get(state, dict_)
else:
old = self.get(state, dict_, passive=PASSIVE_NO_FETCH)
value = self.fire_replace_event(state, dict_, value, old, initiator)
dict_[self.key] = value
def fire_remove_event(self, state, dict_, value, initiator):
if self.trackparent and value is not None:
self.sethasparent(instance_state(value), False)
for ext in self.extensions:
ext.remove(state, value, initiator or self)
state.modified_event(dict_, self, False, value)
def fire_replace_event(self, state, dict_, value, previous, initiator):
if self.trackparent:
if (previous is not value and
previous is not None and
previous is not PASSIVE_NO_RESULT):
self.sethasparent(instance_state(previous), False)
for ext in self.extensions:
value = ext.set(state, value, previous, initiator or self)
state.modified_event(dict_, self, False, previous)
if self.trackparent:
if value is not None:
self.sethasparent(instance_state(value), True)
return value
class CollectionAttributeImpl(AttributeImpl):
"""A collection-holding attribute that instruments changes in membership.
Only handles collections of instrumented objects.
InstrumentedCollectionAttribute holds an arbitrary, user-specified
container object (defaulting to a list) and brokers access to the
CollectionAdapter, a "view" onto that object that presents consistent
bag semantics to the orm layer independent of the user data implementation.
"""
accepts_scalar_loader = False
uses_objects = True
def __init__(self, class_, key, callable_,
typecallable=None, trackparent=False, extension=None,
copy_function=None, compare_function=None, **kwargs):
super(CollectionAttributeImpl, self).__init__(
class_,
key,
callable_,
trackparent=trackparent,
extension=extension,
compare_function=compare_function,
**kwargs)
if copy_function is None:
copy_function = self.__copy
self.copy = copy_function
self.collection_factory = typecallable
def __copy(self, item):
return [y for y in list(collections.collection_adapter(item))]
def get_history(self, state, dict_, passive=PASSIVE_OFF):
current = self.get(state, dict_, passive=passive)
if current is PASSIVE_NO_RESULT:
return HISTORY_BLANK
else:
return History.from_attribute(self, state, current)
def fire_append_event(self, state, dict_, value, initiator):
for ext in self.extensions:
value = ext.append(state, value, initiator or self)
state.modified_event(dict_, self, True, NEVER_SET, passive=PASSIVE_NO_INITIALIZE)
if self.trackparent and value is not None:
self.sethasparent(instance_state(value), True)
return value
def fire_pre_remove_event(self, state, dict_, initiator):
state.modified_event(dict_, self, True, NEVER_SET, passive=PASSIVE_NO_INITIALIZE)
def fire_remove_event(self, state, dict_, value, initiator):
if self.trackparent and value is not None:
self.sethasparent(instance_state(value), False)
for ext in self.extensions:
ext.remove(state, value, initiator or self)
state.modified_event(dict_, self, True, NEVER_SET, passive=PASSIVE_NO_INITIALIZE)
def delete(self, state, dict_):
if self.key not in dict_:
return
state.modified_event(dict_, self, True, NEVER_SET)
collection = self.get_collection(state, state.dict)
collection.clear_with_event()
# TODO: catch key errors, convert to attributeerror?
del dict_[self.key]
def initialize(self, state, dict_):
"""Initialize this attribute with an empty collection."""
_, user_data = self._initialize_collection(state)
dict_[self.key] = user_data
return user_data
def _initialize_collection(self, state):
return state.manager.initialize_collection(
self.key, state, self.collection_factory)
def append(self, state, dict_, value, initiator, passive=PASSIVE_OFF):
if initiator is self:
return
collection = self.get_collection(state, dict_, passive=passive)
if collection is PASSIVE_NO_RESULT:
value = self.fire_append_event(state, dict_, value, initiator)
assert self.key not in dict_, "Collection was loaded during event handling."
state.get_pending(self.key).append(value)
else:
collection.append_with_event(value, initiator)
def remove(self, state, dict_, value, initiator, passive=PASSIVE_OFF):
if initiator is self:
return
collection = self.get_collection(state, state.dict, passive=passive)
if collection is PASSIVE_NO_RESULT:
self.fire_remove_event(state, dict_, value, initiator)
assert self.key not in dict_, "Collection was loaded during event handling."
state.get_pending(self.key).remove(value)
else:
collection.remove_with_event(value, initiator)
def set(self, state, dict_, value, initiator, passive=PASSIVE_OFF):
"""Set a value on the given object.
`initiator` is the ``InstrumentedAttribute`` that initiated the
``set()`` operation and is used to control the depth of a circular
setter operation.
"""
if initiator is self:
return
self._set_iterable(
state, dict_, value,
lambda adapter, i: adapter.adapt_like_to_iterable(i))
def _set_iterable(self, state, dict_, iterable, adapter=None):
"""Set a collection value from an iterable of state-bearers.
``adapter`` is an optional callable invoked with a CollectionAdapter
and the iterable. Should return an iterable of state-bearing
instances suitable for appending via a CollectionAdapter. Can be used
for, e.g., adapting an incoming dictionary into an iterator of values
rather than keys.
"""
# pulling a new collection first so that an adaptation exception does
# not trigger a lazy load of the old collection.
new_collection, user_data = self._initialize_collection(state)
if adapter:
new_values = list(adapter(new_collection, iterable))
else:
new_values = list(iterable)
old = self.get(state, dict_)
# ignore re-assignment of the current collection, as happens
# implicitly with in-place operators (foo.collection |= other)
if old is iterable:
return
state.modified_event(dict_, self, True, old)
old_collection = self.get_collection(state, dict_, old)
dict_[self.key] = user_data
collections.bulk_replace(new_values, old_collection, new_collection)
old_collection.unlink(old)
def set_committed_value(self, state, dict_, value):
"""Set an attribute value on the given instance and 'commit' it."""
collection, user_data = self._initialize_collection(state)
if value:
for item in value:
collection.append_without_event(item)
state.callables.pop(self.key, None)
state.dict[self.key] = user_data
state.commit(dict_, [self.key])
if self.key in state.pending:
# pending items exist. issue a modified event,
# add/remove new items.
state.modified_event(dict_, self, True, user_data)
pending = state.pending.pop(self.key)
added = pending.added_items
removed = pending.deleted_items
for item in added:
collection.append_without_event(item)
for item in removed:
collection.remove_without_event(item)
return user_data
def get_collection(self, state, dict_, user_data=None, passive=PASSIVE_OFF):
"""Retrieve the CollectionAdapter associated with the given state.
Creates a new CollectionAdapter if one does not exist.
"""
if user_data is None:
user_data = self.get(state, dict_, passive=passive)
if user_data is PASSIVE_NO_RESULT:
return user_data
return getattr(user_data, '_sa_adapter')
class GenericBackrefExtension(interfaces.AttributeExtension):
"""An extension which synchronizes a two-way relationship.
A typical two-way relationship is a parent object containing a list of
child objects, where each child object references the parent. The other
are two objects which contain scalar references to each other.
"""
active_history = False
def __init__(self, key):
self.key = key
def set(self, state, child, oldchild, initiator):
if oldchild is child:
return child
if oldchild is not None and oldchild is not PASSIVE_NO_RESULT:
# With lazy=None, there's no guarantee that the full collection is
# present when updating via a backref.
old_state, old_dict = instance_state(oldchild), instance_dict(oldchild)
impl = old_state.get_impl(self.key)
try:
impl.remove(old_state,
old_dict,
state.obj(),
initiator, passive=PASSIVE_NO_FETCH)
except (ValueError, KeyError, IndexError):
pass
if child is not None:
child_state, child_dict = instance_state(child), instance_dict(child)
child_state.get_impl(self.key).append(
child_state,
child_dict,
state.obj(),
initiator, passive=PASSIVE_NO_FETCH)
return child
def append(self, state, child, initiator):
child_state, child_dict = instance_state(child), instance_dict(child)
child_state.get_impl(self.key).append(
child_state,
child_dict,
state.obj(),
initiator, passive=PASSIVE_NO_FETCH)
return child
def remove(self, state, child, initiator):
if child is not None:
child_state, child_dict = instance_state(child), instance_dict(child)
child_state.get_impl(self.key).remove(
child_state,
child_dict,
state.obj(),
initiator, passive=PASSIVE_NO_FETCH)
class Events(object):
def __init__(self):
self.original_init = object.__init__
# Initialize to tuples instead of lists to minimize the memory
# footprint
self.on_init = ()
self.on_init_failure = ()
self.on_load = ()
self.on_resurrect = ()
def run(self, event, *args):
for fn in getattr(self, event):
fn(*args)
def add_listener(self, event, listener):
# not thread safe... problem? mb: nope
bucket = getattr(self, event)
if bucket == ():
setattr(self, event, [listener])
else:
bucket.append(listener)
def remove_listener(self, event, listener):
bucket = getattr(self, event)
bucket.remove(listener)
class ClassManager(dict):
"""tracks state information at the class level."""
MANAGER_ATTR = '_sa_class_manager'
STATE_ATTR = '_sa_instance_state'
event_registry_factory = Events
deferred_scalar_loader = None
def __init__(self, class_):
self.class_ = class_
self.factory = None # where we came from, for inheritance bookkeeping
self.info = {}
self.mapper = None
self.new_init = None
self.mutable_attributes = set()
self.local_attrs = {}
self.originals = {}
for base in class_.__mro__[-2:0:-1]: # reverse, skipping 1st and last
if not isinstance(base, type):
continue
cls_state = manager_of_class(base)
if cls_state:
self.update(cls_state)
self.events = self.event_registry_factory()
self.manage()
self._instrument_init()
def _configure_create_arguments(self,
_source=None,
deferred_scalar_loader=None):
"""Accept extra **kw arguments passed to create_manager_for_cls.
The current contract of ClassManager and other managers is that they
take a single "cls" argument in their constructor (as per
test/orm/instrumentation.py InstrumentationCollisionTest). This
is to provide consistency with the current API of "class manager"
callables and such which may return various ClassManager and
ClassManager-like instances. So create_manager_for_cls sends
in ClassManager-specific arguments via this method once the
non-proxied ClassManager is available.
"""
if _source:
deferred_scalar_loader = _source.deferred_scalar_loader
if deferred_scalar_loader:
self.deferred_scalar_loader = deferred_scalar_loader
def _subclass_manager(self, cls):
"""Create a new ClassManager for a subclass of this ClassManager's class.
This is called automatically when attributes are instrumented so that
the attributes can be propagated to subclasses against their own
class-local manager, without the need for mappers etc. to have already
pre-configured managers for the full class hierarchy. Mappers
can post-configure the auto-generated ClassManager when needed.
"""
manager = manager_of_class(cls)
if manager is None:
manager = _create_manager_for_cls(cls, _source=self)
return manager
def _instrument_init(self):
# TODO: self.class_.__init__ is often the already-instrumented
# __init__ from an instrumented superclass. We still need to make
# our own wrapper, but it would
# be nice to wrap the original __init__ and not our existing wrapper
# of such, since this adds method overhead.
self.events.original_init = self.class_.__init__
self.new_init = _generate_init(self.class_, self)
self.install_member('__init__', self.new_init)
def _uninstrument_init(self):
if self.new_init:
self.uninstall_member('__init__')
self.new_init = None
def _create_instance_state(self, instance):
if self.mutable_attributes:
return state.MutableAttrInstanceState(instance, self)
else:
return state.InstanceState(instance, self)
def manage(self):
"""Mark this instance as the manager for its class."""
setattr(self.class_, self.MANAGER_ATTR, self)
def dispose(self):
"""Dissasociate this manager from its class."""
delattr(self.class_, self.MANAGER_ATTR)
def manager_getter(self):
return attrgetter(self.MANAGER_ATTR)
def instrument_attribute(self, key, inst, propagated=False):
if propagated:
if key in self.local_attrs:
return # don't override local attr with inherited attr
else:
self.local_attrs[key] = inst
self.install_descriptor(key, inst)
self[key] = inst
for cls in self.class_.__subclasses__():
manager = self._subclass_manager(cls)
manager.instrument_attribute(key, inst, True)
def post_configure_attribute(self, key):
pass
def uninstrument_attribute(self, key, propagated=False):
if key not in self:
return
if propagated:
if key in self.local_attrs:
return # don't get rid of local attr
else:
del self.local_attrs[key]
self.uninstall_descriptor(key)
del self[key]
if key in self.mutable_attributes:
self.mutable_attributes.remove(key)
for cls in self.class_.__subclasses__():
manager = self._subclass_manager(cls)
manager.uninstrument_attribute(key, True)
def unregister(self):
"""remove all instrumentation established by this ClassManager."""
self._uninstrument_init()
self.mapper = self.events = None
self.info.clear()
for key in list(self):
if key in self.local_attrs:
self.uninstrument_attribute(key)
def install_descriptor(self, key, inst):
if key in (self.STATE_ATTR, self.MANAGER_ATTR):
raise KeyError("%r: requested attribute name conflicts with "
"instrumentation attribute of the same name." % key)
setattr(self.class_, key, inst)
def uninstall_descriptor(self, key):
delattr(self.class_, key)
def install_member(self, key, implementation):
if key in (self.STATE_ATTR, self.MANAGER_ATTR):
raise KeyError("%r: requested attribute name conflicts with "
"instrumentation attribute of the same name." % key)
self.originals.setdefault(key, getattr(self.class_, key, None))
setattr(self.class_, key, implementation)
def uninstall_member(self, key):
original = self.originals.pop(key, None)
if original is not None:
setattr(self.class_, key, original)
def instrument_collection_class(self, key, collection_class):
return collections.prepare_instrumentation(collection_class)
def initialize_collection(self, key, state, factory):
user_data = factory()
adapter = collections.CollectionAdapter(
self.get_impl(key), state, user_data)
return adapter, user_data
def is_instrumented(self, key, search=False):
if search:
return key in self
else:
return key in self.local_attrs
def get_impl(self, key):
return self[key].impl
@property
def attributes(self):
return self.itervalues()
## InstanceState management
def new_instance(self, state=None):
instance = self.class_.__new__(self.class_)
setattr(instance, self.STATE_ATTR, state or self._create_instance_state(instance))
return instance
def setup_instance(self, instance, state=None):
setattr(instance, self.STATE_ATTR, state or self._create_instance_state(instance))
def teardown_instance(self, instance):
delattr(instance, self.STATE_ATTR)
def _new_state_if_none(self, instance):
"""Install a default InstanceState if none is present.
A private convenience method used by the __init__ decorator.
"""
if hasattr(instance, self.STATE_ATTR):
return False
else:
state = self._create_instance_state(instance)
setattr(instance, self.STATE_ATTR, state)
return state
def state_getter(self):
"""Return a (instance) -> InstanceState callable.
"state getter" callables should raise either KeyError or
AttributeError if no InstanceState could be found for the
instance.
"""
return attrgetter(self.STATE_ATTR)
def dict_getter(self):
return attrgetter('__dict__')
def has_state(self, instance):
return hasattr(instance, self.STATE_ATTR)
def has_parent(self, state, key, optimistic=False):
"""TODO"""
return self.get_impl(key).hasparent(state, optimistic=optimistic)
def __nonzero__(self):
"""All ClassManagers are non-zero regardless of attribute state."""
return True
def __repr__(self):
return '<%s of %r at %x>' % (
self.__class__.__name__, self.class_, id(self))
class _ClassInstrumentationAdapter(ClassManager):
"""Adapts a user-defined InstrumentationManager to a ClassManager."""
def __init__(self, class_, override, **kw):
self._adapted = override
self._get_state = self._adapted.state_getter(class_)
self._get_dict = self._adapted.dict_getter(class_)
ClassManager.__init__(self, class_, **kw)
def manage(self):
self._adapted.manage(self.class_, self)
def dispose(self):
self._adapted.dispose(self.class_)
def manager_getter(self):
return self._adapted.manager_getter(self.class_)
def instrument_attribute(self, key, inst, propagated=False):
ClassManager.instrument_attribute(self, key, inst, propagated)
if not propagated:
self._adapted.instrument_attribute(self.class_, key, inst)
def post_configure_attribute(self, key):
self._adapted.post_configure_attribute(self.class_, key, self[key])
def install_descriptor(self, key, inst):
self._adapted.install_descriptor(self.class_, key, inst)
def uninstall_descriptor(self, key):
self._adapted.uninstall_descriptor(self.class_, key)
def install_member(self, key, implementation):
self._adapted.install_member(self.class_, key, implementation)
def uninstall_member(self, key):
self._adapted.uninstall_member(self.class_, key)
def instrument_collection_class(self, key, collection_class):
return self._adapted.instrument_collection_class(
self.class_, key, collection_class)
def initialize_collection(self, key, state, factory):
delegate = getattr(self._adapted, 'initialize_collection', None)
if delegate:
return delegate(key, state, factory)
else:
return ClassManager.initialize_collection(self, key, state, factory)
def new_instance(self, state=None):
instance = self.class_.__new__(self.class_)
self.setup_instance(instance, state)
return instance
def _new_state_if_none(self, instance):
"""Install a default InstanceState if none is present.
A private convenience method used by the __init__ decorator.
"""
if self.has_state(instance):
return False
else:
return self.setup_instance(instance)
def setup_instance(self, instance, state=None):
self._adapted.initialize_instance_dict(self.class_, instance)
if state is None:
state = self._create_instance_state(instance)
# the given instance is assumed to have no state
self._adapted.install_state(self.class_, instance, state)
return state
def teardown_instance(self, instance):
self._adapted.remove_state(self.class_, instance)
def has_state(self, instance):
try:
state = self._get_state(instance)
except exc.NO_STATE:
return False
else:
return True
def state_getter(self):
return self._get_state
def dict_getter(self):
return self._get_dict
class History(tuple):
"""A 3-tuple of added, unchanged and deleted values.
Each tuple member is an iterable sequence.
"""
__slots__ = ()
added = property(itemgetter(0))
unchanged = property(itemgetter(1))
deleted = property(itemgetter(2))
def __new__(cls, added, unchanged, deleted):
return tuple.__new__(cls, (added, unchanged, deleted))
def __nonzero__(self):
return self != HISTORY_BLANK
def empty(self):
return not bool(
(self.added or self.deleted)
or self.unchanged and self.unchanged != [None]
)
def sum(self):
return (self.added or []) +\
(self.unchanged or []) +\
(self.deleted or [])
def non_deleted(self):
return (self.added or []) +\
(self.unchanged or [])
def non_added(self):
return (self.unchanged or []) +\
(self.deleted or [])
def has_changes(self):
return bool(self.added or self.deleted)
def as_state(self):
return History(
[(c is not None and c is not PASSIVE_NO_RESULT)
and instance_state(c) or None
for c in self.added],
[(c is not None and c is not PASSIVE_NO_RESULT)
and instance_state(c) or None
for c in self.unchanged],
[(c is not None and c is not PASSIVE_NO_RESULT)
and instance_state(c) or None
for c in self.deleted],
)
@classmethod
def from_attribute(cls, attribute, state, current):
original = state.committed_state.get(attribute.key, NEVER_SET)
if hasattr(attribute, 'get_collection'):
current = attribute.get_collection(state, state.dict, current)
if original is NO_VALUE:
return cls(list(current), (), ())
elif original is NEVER_SET:
return cls((), list(current), ())
else:
current_set = util.IdentitySet(current)
original_set = util.IdentitySet(original)
# ensure duplicates are maintained
return cls(
[x for x in current if x not in original_set],
[x for x in current if x in original_set],
[x for x in original if x not in current_set]
)
else:
if current is NO_VALUE:
if (original is not None and
original is not NEVER_SET and
original is not NO_VALUE):
deleted = [original]
else:
deleted = ()
return cls((), (), deleted)
elif original is NO_VALUE:
return cls([current], (), ())
elif (original is NEVER_SET or
attribute.is_equal(current, original) is True):
# dont let ClauseElement expressions here trip things up
return cls((), [current], ())
else:
if original is not None:
deleted = [original]
else:
deleted = ()
return cls([current], (), deleted)
HISTORY_BLANK = History(None, None, None)
def get_history(obj, key, **kwargs):
"""Return a History record for the given object and attribute key.
obj is an instrumented object instance. An InstanceState
is accepted directly for backwards compatibility but
this usage is deprecated.
"""
return get_state_history(instance_state(obj), key, **kwargs)
def get_state_history(state, key, **kwargs):
return state.get_history(key, **kwargs)
def has_parent(cls, obj, key, optimistic=False):
"""TODO"""
manager = manager_of_class(cls)
state = instance_state(obj)
return manager.has_parent(state, key, optimistic)
def register_class(class_, **kw):
"""Register class instrumentation.
Returns the existing or newly created class manager.
"""
manager = manager_of_class(class_)
if manager is None:
manager = _create_manager_for_cls(class_, **kw)
return manager
def unregister_class(class_):
"""Unregister class instrumentation."""
instrumentation_registry.unregister(class_)
def register_attribute(class_, key, **kw):
proxy_property = kw.pop('proxy_property', None)
comparator = kw.pop('comparator', None)
parententity = kw.pop('parententity', None)
doc = kw.pop('doc', None)
register_descriptor(class_, key, proxy_property, comparator, parententity, doc=doc)
if not proxy_property:
register_attribute_impl(class_, key, **kw)
def register_attribute_impl(class_, key,
uselist=False, callable_=None,
useobject=False, mutable_scalars=False,
impl_class=None, **kw):
manager = manager_of_class(class_)
if uselist:
factory = kw.pop('typecallable', None)
typecallable = manager.instrument_collection_class(
key, factory or list)
else:
typecallable = kw.pop('typecallable', None)
if impl_class:
impl = impl_class(class_, key, typecallable, **kw)
elif uselist:
impl = CollectionAttributeImpl(class_, key, callable_,
typecallable=typecallable, **kw)
elif useobject:
impl = ScalarObjectAttributeImpl(class_, key, callable_, **kw)
elif mutable_scalars:
impl = MutableScalarAttributeImpl(class_, key, callable_,
class_manager=manager, **kw)
else:
impl = ScalarAttributeImpl(class_, key, callable_, **kw)
manager[key].impl = impl
manager.post_configure_attribute(key)
def register_descriptor(class_, key, proxy_property=None, comparator=None,
parententity=None, property_=None, doc=None):
manager = manager_of_class(class_)
if proxy_property:
proxy_type = proxied_attribute_factory(proxy_property)
descriptor = proxy_type(key, proxy_property, comparator, parententity)
else:
descriptor = InstrumentedAttribute(key, comparator=comparator, parententity=parententity)
descriptor.__doc__ = doc
manager.instrument_attribute(key, descriptor)
def unregister_attribute(class_, key):
manager_of_class(class_).uninstrument_attribute(key)
def init_collection(obj, key):
"""Initialize a collection attribute and return the collection adapter.
This function is used to provide direct access to collection internals
for a previously unloaded attribute. e.g.::
collection_adapter = init_collection(someobject, 'elements')
for elem in values:
collection_adapter.append_without_event(elem)
For an easier way to do the above, see :func:`~sqlalchemy.orm.attributes.set_committed_value`.
obj is an instrumented object instance. An InstanceState
is accepted directly for backwards compatibility but
this usage is deprecated.
"""
state = instance_state(obj)
dict_ = state.dict
return init_state_collection(state, dict_, key)
def init_state_collection(state, dict_, key):
"""Initialize a collection attribute and return the collection adapter."""
attr = state.get_impl(key)
user_data = attr.initialize(state, dict_)
return attr.get_collection(state, dict_, user_data)
def set_committed_value(instance, key, value):
"""Set the value of an attribute with no history events.
Cancels any previous history present. The value should be
a scalar value for scalar-holding attributes, or
an iterable for any collection-holding attribute.
This is the same underlying method used when a lazy loader
fires off and loads additional data from the database.
In particular, this method can be used by application code
which has loaded additional attributes or collections through
separate queries, which can then be attached to an instance
as though it were part of its original loaded state.
"""
state, dict_ = instance_state(instance), instance_dict(instance)
state.get_impl(key).set_committed_value(state, dict_, value)
def set_attribute(instance, key, value):
"""Set the value of an attribute, firing history events.
This function may be used regardless of instrumentation
applied directly to the class, i.e. no descriptors are required.
Custom attribute management schemes will need to make usage
of this method to establish attribute state as understood
by SQLAlchemy.
"""
state, dict_ = instance_state(instance), instance_dict(instance)
state.get_impl(key).set(state, dict_, value, None)
def get_attribute(instance, key):
"""Get the value of an attribute, firing any callables required.
This function may be used regardless of instrumentation
applied directly to the class, i.e. no descriptors are required.
Custom attribute management schemes will need to make usage
of this method to make usage of attribute state as understood
by SQLAlchemy.
"""
state, dict_ = instance_state(instance), instance_dict(instance)
return state.get_impl(key).get(state, dict_)
def del_attribute(instance, key):
"""Delete the value of an attribute, firing history events.
This function may be used regardless of instrumentation
applied directly to the class, i.e. no descriptors are required.
Custom attribute management schemes will need to make usage
of this method to establish attribute state as understood
by SQLAlchemy.
"""
state, dict_ = instance_state(instance), instance_dict(instance)
state.get_impl(key).delete(state, dict_)
def is_instrumented(instance, key):
"""Return True if the given attribute on the given instance is instrumented
by the attributes package.
This function may be used regardless of instrumentation
applied directly to the class, i.e. no descriptors are required.
"""
return manager_of_class(instance.__class__).is_instrumented(key, search=True)
class InstrumentationRegistry(object):
"""Private instrumentation registration singleton.
All classes are routed through this registry
when first instrumented, however the InstrumentationRegistry
is not actually needed unless custom ClassManagers are in use.
"""
_manager_finders = weakref.WeakKeyDictionary()
_state_finders = util.WeakIdentityMapping()
_dict_finders = util.WeakIdentityMapping()
_extended = False
def create_manager_for_cls(self, class_, **kw):
assert class_ is not None
assert manager_of_class(class_) is None
for finder in instrumentation_finders:
factory = finder(class_)
if factory is not None:
break
else:
factory = ClassManager
existing_factories = self._collect_management_factories_for(class_).\
difference([factory])
if existing_factories:
raise TypeError(
"multiple instrumentation implementations specified "
"in %s inheritance hierarchy: %r" % (
class_.__name__, list(existing_factories)))
manager = factory(class_)
if not isinstance(manager, ClassManager):
manager = _ClassInstrumentationAdapter(class_, manager)
if factory != ClassManager and not self._extended:
# somebody invoked a custom ClassManager.
# reinstall global "getter" functions with the more
# expensive ones.
self._extended = True
_install_lookup_strategy(self)
manager._configure_create_arguments(**kw)
manager.factory = factory
self._manager_finders[class_] = manager.manager_getter()
self._state_finders[class_] = manager.state_getter()
self._dict_finders[class_] = manager.dict_getter()
return manager
def _collect_management_factories_for(self, cls):
"""Return a collection of factories in play or specified for a hierarchy.
Traverses the entire inheritance graph of a cls and returns a collection
of instrumentation factories for those classes. Factories are extracted
from active ClassManagers, if available, otherwise
instrumentation_finders is consulted.
"""
hierarchy = util.class_hierarchy(cls)
factories = set()
for member in hierarchy:
manager = manager_of_class(member)
if manager is not None:
factories.add(manager.factory)
else:
for finder in instrumentation_finders:
factory = finder(member)
if factory is not None:
break
else:
factory = None
factories.add(factory)
factories.discard(None)
return factories
def manager_of_class(self, cls):
# this is only called when alternate instrumentation has been established
if cls is None:
return None
try:
finder = self._manager_finders[cls]
except KeyError:
return None
else:
return finder(cls)
def state_of(self, instance):
# this is only called when alternate instrumentation has been established
if instance is None:
raise AttributeError("None has no persistent state.")
try:
return self._state_finders[instance.__class__](instance)
except KeyError:
raise AttributeError("%r is not instrumented" % instance.__class__)
def dict_of(self, instance):
# this is only called when alternate instrumentation has been established
if instance is None:
raise AttributeError("None has no persistent state.")
try:
return self._dict_finders[instance.__class__](instance)
except KeyError:
raise AttributeError("%r is not instrumented" % instance.__class__)
def unregister(self, class_):
if class_ in self._manager_finders:
manager = self.manager_of_class(class_)
manager.unregister()
manager.dispose()
del self._manager_finders[class_]
del self._state_finders[class_]
del self._dict_finders[class_]
if ClassManager.MANAGER_ATTR in class_.__dict__:
delattr(class_, ClassManager.MANAGER_ATTR)
instrumentation_registry = InstrumentationRegistry()
def _install_lookup_strategy(implementation):
"""Replace global class/object management functions
with either faster or more comprehensive implementations,
based on whether or not extended class instrumentation
has been detected.
This function is called only by InstrumentationRegistry()
and unit tests specific to this behavior.
"""
global instance_state, instance_dict, manager_of_class
if implementation is util.symbol('native'):
instance_state = attrgetter(ClassManager.STATE_ATTR)
instance_dict = attrgetter("__dict__")
def manager_of_class(cls):
return cls.__dict__.get(ClassManager.MANAGER_ATTR, None)
else:
instance_state = instrumentation_registry.state_of
instance_dict = instrumentation_registry.dict_of
manager_of_class = instrumentation_registry.manager_of_class
_create_manager_for_cls = instrumentation_registry.create_manager_for_cls
# Install default "lookup" strategies. These are basically
# very fast attrgetters for key attributes.
# When a custom ClassManager is installed, more expensive per-class
# strategies are copied over these.
_install_lookup_strategy(util.symbol('native'))
def find_native_user_instrumentation_hook(cls):
"""Find user-specified instrumentation management for a class."""
return getattr(cls, INSTRUMENTATION_MANAGER, None)
instrumentation_finders.append(find_native_user_instrumentation_hook)
def _generate_init(class_, class_manager):
"""Build an __init__ decorator that triggers ClassManager events."""
# TODO: we should use the ClassManager's notion of the
# original '__init__' method, once ClassManager is fixed
# to always reference that.
original__init__ = class_.__init__
assert original__init__
# Go through some effort here and don't change the user's __init__
# calling signature.
# FIXME: need to juggle local names to avoid constructor argument
# clashes.
func_body = """\
def __init__(%(apply_pos)s):
new_state = class_manager._new_state_if_none(%(self_arg)s)
if new_state:
return new_state.initialize_instance(%(apply_kw)s)
else:
return original__init__(%(apply_kw)s)
"""
func_vars = util.format_argspec_init(original__init__, grouped=False)
func_text = func_body % func_vars
# Py3K
#func_defaults = getattr(original__init__, '__defaults__', None)
# Py2K
func = getattr(original__init__, 'im_func', original__init__)
func_defaults = getattr(func, 'func_defaults', None)
# end Py2K
env = locals().copy()
exec func_text in env
__init__ = env['__init__']
__init__.__doc__ = original__init__.__doc__
if func_defaults:
__init__.func_defaults = func_defaults
return __init__
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