# orm/attributes.py
# Copyright (C) 2005-2013 the SQLAlchemy authors and contributors <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: http://www.opensource.org/licenses/mit-license.php
"""Defines instrumentation for class attributes and their interaction
with instances.
This module is usually not directly visible to user applications, but
defines a large part of the ORM's interactivity.
"""
import operator
from operator import itemgetter
from .. import util, event, inspection
from . import interfaces, collections, events, exc as orm_exc
from .instrumentation import instance_state, instance_dict, manager_of_class
orm_util = util.importlater("sqlalchemy.orm", "util")
PASSIVE_NO_RESULT = util.symbol('PASSIVE_NO_RESULT',
"""Symbol returned by a loader callable or other attribute/history
retrieval operation when a value could not be determined, based
on loader callable flags.
"""
)
ATTR_WAS_SET = util.symbol('ATTR_WAS_SET',
"""Symbol returned by a loader callable to indicate the
retrieved value, or values, were assigned to their attributes
on the target object.
""")
ATTR_EMPTY = util.symbol('ATTR_EMPTY',
"""Symbol used internally to indicate an attribute had no callable.
""")
NO_VALUE = util.symbol('NO_VALUE',
"""Symbol which may be placed as the 'previous' value of an attribute,
indicating no value was loaded for an attribute when it was modified,
and flags indicated we were not to load it.
"""
)
NEVER_SET = util.symbol('NEVER_SET',
"""Symbol which may be placed as the 'previous' value of an attribute
indicating that the attribute had not been assigned to previously.
"""
)
NO_CHANGE = util.symbol("NO_CHANGE",
"""No callables or SQL should be emitted on attribute access
and no state should change""", canonical=0
)
CALLABLES_OK = util.symbol("CALLABLES_OK",
"""Loader callables can be fired off if a value
is not present.""", canonical=1
)
SQL_OK = util.symbol("SQL_OK",
"""Loader callables can emit SQL at least on scalar value
attributes.""", canonical=2)
RELATED_OBJECT_OK = util.symbol("RELATED_OBJECT_OK",
"""callables can use SQL to load related objects as well
as scalar value attributes.
""", canonical=4
)
INIT_OK = util.symbol("INIT_OK",
"""Attributes should be initialized with a blank
value (None or an empty collection) upon get, if no other
value can be obtained.
""", canonical=8
)
NON_PERSISTENT_OK = util.symbol("NON_PERSISTENT_OK",
"""callables can be emitted if the parent is not persistent.""",
canonical=16
)
LOAD_AGAINST_COMMITTED = util.symbol("LOAD_AGAINST_COMMITTED",
"""callables should use committed values as primary/foreign keys during a load
""", canonical=32
)
# pre-packaged sets of flags used as inputs
PASSIVE_OFF = util.symbol("PASSIVE_OFF",
"Callables can be emitted in all cases.",
canonical=(RELATED_OBJECT_OK | NON_PERSISTENT_OK |
INIT_OK | CALLABLES_OK | SQL_OK)
)
PASSIVE_RETURN_NEVER_SET = util.symbol("PASSIVE_RETURN_NEVER_SET",
"""PASSIVE_OFF ^ INIT_OK""",
canonical=PASSIVE_OFF ^ INIT_OK
)
PASSIVE_NO_INITIALIZE = util.symbol("PASSIVE_NO_INITIALIZE",
"PASSIVE_RETURN_NEVER_SET ^ CALLABLES_OK",
canonical=PASSIVE_RETURN_NEVER_SET ^ CALLABLES_OK
)
PASSIVE_NO_FETCH = util.symbol("PASSIVE_NO_FETCH",
"PASSIVE_OFF ^ SQL_OK",
canonical=PASSIVE_OFF ^ SQL_OK
)
PASSIVE_NO_FETCH_RELATED = util.symbol("PASSIVE_NO_FETCH_RELATED",
"PASSIVE_OFF ^ RELATED_OBJECT_OK",
canonical=PASSIVE_OFF ^ RELATED_OBJECT_OK
)
PASSIVE_ONLY_PERSISTENT = util.symbol("PASSIVE_ONLY_PERSISTENT",
"PASSIVE_OFF ^ NON_PERSISTENT_OK",
canonical=PASSIVE_OFF ^ NON_PERSISTENT_OK
)
class QueryableAttribute(interfaces._MappedAttribute,
interfaces._InspectionAttr,
interfaces.PropComparator):
"""Base class for :term:`descriptor` objects that intercept
attribute events on behalf of a :class:`.MapperProperty`
object. The actual :class:`.MapperProperty` is accessible
via the :attr:`.QueryableAttribute.property`
attribute.
.. seealso::
:class:`.InstrumentedAttribute`
:class:`.MapperProperty`
:attr:`.Mapper.all_orm_descriptors`
:attr:`.Mapper.attrs`
"""
is_attribute = True
def __init__(self, class_, key, impl=None,
comparator=None, parententity=None,
of_type=None):
self.class_ = class_
self.key = key
self.impl = impl
self.comparator = comparator
self._parententity = parententity
self._of_type = of_type
manager = manager_of_class(class_)
# manager is None in the case of AliasedClass
if manager:
# propagate existing event listeners from
# immediate superclass
for base in manager._bases:
if key in base:
self.dispatch._update(base[key].dispatch)
dispatch = event.dispatcher(events.AttributeEvents)
dispatch.dispatch_cls._active_history = False
@util.memoized_property
def _supports_population(self):
return self.impl.supports_population
def get_history(self, instance, passive=PASSIVE_OFF):
return self.impl.get_history(instance_state(instance),
instance_dict(instance), passive)
def __selectable__(self):
# TODO: conditionally attach this method based on clause_element ?
return self
@util.memoized_property
def info(self):
"""Return the 'info' dictionary for the underlying SQL element.
The behavior here is as follows:
* If the attribute is a column-mapped property, i.e.
:class:`.ColumnProperty`, which is mapped directly
to a schema-level :class:`.Column` object, this attribute
will return the :attr:`.SchemaItem.info` dictionary associated
with the core-level :class:`.Column` object.
* If the attribute is a :class:`.ColumnProperty` but is mapped to
any other kind of SQL expression other than a :class:`.Column`,
the attribute will refer to the :attr:`.MapperProperty.info` dictionary
associated directly with the :class:`.ColumnProperty`, assuming the SQL
expression itself does not have it's own ``.info`` attribute
(which should be the case, unless a user-defined SQL construct
has defined one).
* If the attribute refers to any other kind of :class:`.MapperProperty`,
including :class:`.RelationshipProperty`, the attribute will refer
to the :attr:`.MapperProperty.info` dictionary associated with
that :class:`.MapperProperty`.
* To access the :attr:`.MapperProperty.info` dictionary of the :class:`.MapperProperty`
unconditionally, including for a :class:`.ColumnProperty` that's
associated directly with a :class:`.schema.Column`, the attribute
can be referred to using :attr:`.QueryableAttribute.property`
attribute, as ``MyClass.someattribute.property.info``.
.. versionadded:: 0.8.0
.. seealso::
:attr:`.SchemaItem.info`
:attr:`.MapperProperty.info`
"""
return self.comparator.info
@util.memoized_property
def parent(self):
"""Return an inspection instance representing the parent.
This will be either an instance of :class:`.Mapper`
or :class:`.AliasedInsp`, depending upon the nature
of the parent entity which this attribute is associated
with.
"""
return inspection.inspect(self._parententity)
@property
def expression(self):
return self.comparator.__clause_element__()
def __clause_element__(self):
return self.comparator.__clause_element__()
def of_type(self, cls):
return QueryableAttribute(
self.class_,
self.key,
self.impl,
self.comparator.of_type(cls),
self._parententity,
of_type=cls)
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) is not False
def __getattr__(self, key):
try:
return getattr(self.comparator, key)
except AttributeError:
raise AttributeError(
'Neither %r object nor %r object associated with %s '
'has an attribute %r' % (
type(self).__name__,
type(self.comparator).__name__,
self,
key)
)
def __str__(self):
return "%s.%s" % (self.class_.__name__, self.key)
@util.memoized_property
def property(self):
"""Return the :class:`.MapperProperty` associated with this
:class:`.QueryableAttribute`.
Return values here will commonly be instances of
:class:`.ColumnProperty` or :class:`.RelationshipProperty`.
"""
return self.comparator.property
inspection._self_inspects(QueryableAttribute)
class InstrumentedAttribute(QueryableAttribute):
"""Class bound instrumented attribute which adds basic
:term:`descriptor` methods.
See :class:`.QueryableAttribute` for a description of most features.
"""
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
dict_ = instance_dict(instance)
if self._supports_population and self.key in dict_:
return dict_[self.key]
else:
return self.impl.get(instance_state(instance), dict_)
def create_proxied_attribute(descriptor):
"""Create an QueryableAttribute / user descriptor hybrid.
Returns a new QueryableAttribute type that delegates descriptor
behavior and getattr() to the given descriptor.
"""
# TODO: can move this to descriptor_props if the need for this
# function is removed from ext/hybrid.py
class Proxy(QueryableAttribute):
"""Presents the :class:`.QueryableAttribute` interface as a
proxy on top of a Python descriptor / :class:`.PropComparator`
combination.
"""
def __init__(self, class_, key, descriptor,
comparator,
adapter=None, doc=None,
original_property=None):
self.class_ = class_
self.key = key
self.descriptor = descriptor
self.original_property = original_property
self._comparator = comparator
self.adapter = adapter
self.__doc__ = doc
@property
def property(self):
return self.comparator.property
@util.memoized_property
def comparator(self):
if util.callable(self._comparator):
self._comparator = self._comparator()
if self.adapter:
self._comparator = self._comparator.adapted(self.adapter)
return self._comparator
def adapted(self, adapter):
"""Proxy adapted() for the use case of AliasedClass calling
adapted.
"""
return self.__class__(self.class_, self.key, self.descriptor,
self._comparator,
adapter)
def __get__(self, instance, owner):
if instance is None:
return self
else:
return self.descriptor.__get__(instance, owner)
def __str__(self):
return "%s.%s" % (self.class_.__name__, self.key)
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 associated with %s '
'has an attribute %r' % (
type(descriptor).__name__,
type(self.comparator).__name__,
self,
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_, dispatch, 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. Deprecated.
The event package is now used.
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.dispatch = dispatch
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
# TODO: pass in the manager here
# instead of doing a lookup
attr = manager_of_class(class_)[key]
for ext in util.to_list(extension or []):
ext._adapt_listener(attr, ext)
if active_history:
self.dispatch._active_history = True
self.expire_missing = expire_missing
def __str__(self):
return "%s.%s" % (self.class_.__name__, self.key)
def _get_active_history(self):
"""Backwards compat for impl.active_history"""
return self.dispatch._active_history
def _set_active_history(self, value):
self.dispatch._active_history = value
active_history = property(_get_active_history, _set_active_history)
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.
"""
msg = "This AttributeImpl is not configured to track parents."
assert self.trackparent, msg
return state.parents.get(id(self.parent_token), optimistic) \
is not False
def sethasparent(self, state, parent_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``.
"""
msg = "This AttributeImpl is not configured to track parents."
assert self.trackparent, msg
id_ = id(self.parent_token)
if value:
state.parents[id_] = parent_state
else:
if id_ in state.parents:
last_parent = state.parents[id_]
if last_parent is not False and \
last_parent.key != parent_state.key:
if last_parent.obj() is None:
raise orm_exc.StaleDataError(
"Removing state %s from parent "
"state %s along attribute '%s', "
"but the parent record "
"has gone stale, can't be sure this "
"is the most recent parent." %
(orm_util.state_str(state),
orm_util.state_str(parent_state),
self.key))
return
state.parents[id_] = False
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_all_pending(self, state, dict_):
"""Return a list of tuples of (state, obj)
for all objects in this attribute's current state
+ history.
Only applies to object-based attributes.
This is an inlining of existing functionality
which roughly corresponds to:
get_state_history(
state,
key,
passive=PASSIVE_NO_INITIALIZE).sum()
"""
raise NotImplementedError()
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.
"""
if self.key in dict_:
return dict_[self.key]
else:
# if history present, don't load
key = self.key
if key not in state.committed_state or \
state.committed_state[key] is NEVER_SET:
if not passive & CALLABLES_OK:
return PASSIVE_NO_RESULT
if key in state.callables:
callable_ = state.callables[key]
value = callable_(state, passive)
elif self.callable_:
value = self.callable_(state, passive)
else:
value = ATTR_EMPTY
if value is PASSIVE_NO_RESULT or value is NEVER_SET:
return value
elif value is ATTR_WAS_SET:
try:
return dict_[key]
except KeyError:
# TODO: no test coverage here.
raise KeyError(
"Deferred loader for attribute "
"%r failed to populate "
"correctly" % key)
elif value is not ATTR_EMPTY:
return self.set_committed_value(state, dict_, value)
if not passive & INIT_OK:
return NEVER_SET
else:
# 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, check_old=value)
def pop(self, state, dict_, value, initiator, passive=PASSIVE_OFF):
self.set(state, dict_, None, initiator,
passive=passive, check_old=value, pop=True)
def set(self, state, dict_, value, initiator,
passive=PASSIVE_OFF, check_old=None, pop=False):
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:
value = state.committed_state[self.key]
if value is NO_VALUE:
return None
else:
return value
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."""
dict_[self.key] = value
state._commit(dict_, [self.key])
return value
class ScalarAttributeImpl(AttributeImpl):
"""represents a scalar value-holding InstrumentedAttribute."""
accepts_scalar_loader = True
uses_objects = False
supports_population = True
collection = False
def delete(self, state, dict_):
# TODO: catch key errors, convert to attributeerror?
if self.dispatch._active_history:
old = self.get(state, dict_, PASSIVE_RETURN_NEVER_SET)
else:
old = dict_.get(self.key, NO_VALUE)
if self.dispatch.remove:
self.fire_remove_event(state, dict_, old, None)
state._modified_event(dict_, self, old)
del dict_[self.key]
def get_history(self, state, dict_, passive=PASSIVE_OFF):
return History.from_scalar_attribute(
self, state, dict_.get(self.key, NO_VALUE))
def set(self, state, dict_, value, initiator,
passive=PASSIVE_OFF, check_old=None, pop=False):
if initiator and initiator.parent_token is self.parent_token:
return
if self.dispatch._active_history:
old = self.get(state, dict_, PASSIVE_RETURN_NEVER_SET)
else:
old = dict_.get(self.key, NO_VALUE)
if self.dispatch.set:
value = self.fire_replace_event(state, dict_,
value, old, initiator)
state._modified_event(dict_, self, old)
dict_[self.key] = value
def fire_replace_event(self, state, dict_, value, previous, initiator):
for fn in self.dispatch.set:
value = fn(state, value, previous, initiator or self)
return value
def fire_remove_event(self, state, dict_, value, initiator):
for fn in self.dispatch.remove:
fn(state, value, initiator or self)
@property
def type(self):
self.property.columns[0].type
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
supports_population = True
collection = False
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_object_attribute(self, state, dict_[self.key])
else:
if passive & INIT_OK:
passive ^= INIT_OK
current = self.get(state, dict_, passive=passive)
if current is PASSIVE_NO_RESULT:
return HISTORY_BLANK
else:
return History.from_object_attribute(self, state, current)
def get_all_pending(self, state, dict_):
if self.key in dict_:
current = dict_[self.key]
if current is not None:
ret = [(instance_state(current), current)]
else:
ret = [(None, None)]
if self.key in state.committed_state:
original = state.committed_state[self.key]
if original not in (NEVER_SET, PASSIVE_NO_RESULT, None) and \
original is not current:
ret.append((instance_state(original), original))
return ret
else:
return []
def set(self, state, dict_, value, initiator,
passive=PASSIVE_OFF, check_old=None, pop=False):
"""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 and initiator.parent_token is self.parent_token:
return
if self.dispatch._active_history:
old = self.get(state, dict_, passive=PASSIVE_ONLY_PERSISTENT)
else:
old = self.get(state, dict_, passive=PASSIVE_NO_FETCH)
if check_old is not None and \
old is not PASSIVE_NO_RESULT and \
check_old is not old:
if pop:
return
else:
raise ValueError(
"Object %s not associated with %s on attribute '%s'" % (
orm_util.instance_str(check_old),
orm_util.state_str(state),
self.key
))
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), state, False)
for fn in self.dispatch.remove:
fn(state, value, initiator or self)
state._modified_event(dict_, self, 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), state, False)
for fn in self.dispatch.set:
value = fn(state, value, previous, initiator or self)
state._modified_event(dict_, self, previous)
if self.trackparent:
if value is not None:
self.sethasparent(instance_state(value), state, 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
supports_population = True
collection = True
def __init__(self, class_, key, callable_, dispatch,
typecallable=None, trackparent=False, extension=None,
copy_function=None, compare_function=None, **kwargs):
super(CollectionAttributeImpl, self).__init__(
class_,
key,
callable_, dispatch,
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_collection(self, state, current)
def get_all_pending(self, state, dict_):
if self.key not in dict_:
return []
current = dict_[self.key]
current = getattr(current, '_sa_adapter')
if self.key in state.committed_state:
original = state.committed_state[self.key]
if original not in (NO_VALUE, NEVER_SET):
current_states = [((c is not None) and
instance_state(c) or None, c)
for c in current]
original_states = [((c is not None) and
instance_state(c) or None, c)
for c in original]
current_set = dict(current_states)
original_set = dict(original_states)
return \
[(s, o) for s, o in current_states
if s not in original_set] + \
[(s, o) for s, o in current_states
if s in original_set] + \
[(s, o) for s, o in original_states
if s not in current_set]
return [(instance_state(o), o) for o in current]
def fire_append_event(self, state, dict_, value, initiator):
for fn in self.dispatch.append:
value = fn(state, value, initiator or self)
state._modified_event(dict_, self, NEVER_SET, True)
if self.trackparent and value is not None:
self.sethasparent(instance_state(value), state, True)
return value
def fire_pre_remove_event(self, state, dict_, initiator):
state._modified_event(dict_, self, NEVER_SET, True)
def fire_remove_event(self, state, dict_, value, initiator):
if self.trackparent and value is not None:
self.sethasparent(instance_state(value), state, False)
for fn in self.dispatch.remove:
fn(state, value, initiator or self)
state._modified_event(dict_, self, NEVER_SET, True)
def delete(self, state, dict_):
if self.key not in dict_:
return
state._modified_event(dict_, self, NEVER_SET, True)
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 and initiator.parent_token is self.parent_token:
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_mutation(self.key).append(value)
else:
collection.append_with_event(value, initiator)
def remove(self, state, dict_, value, initiator, passive=PASSIVE_OFF):
if initiator and initiator.parent_token is self.parent_token:
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_mutation(self.key).remove(value)
else:
collection.remove_with_event(value, initiator)
def pop(self, state, dict_, value, initiator, passive=PASSIVE_OFF):
try:
# TODO: better solution here would be to add
# a "popper" role to collections.py to complement
# "remover".
self.remove(state, dict_, value, initiator, passive=passive)
except (ValueError, KeyError, IndexError):
pass
def set(self, state, dict_, value, initiator,
passive=PASSIVE_OFF, pop=False):
"""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 and initiator.parent_token is self.parent_token:
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_, passive=PASSIVE_ONLY_PERSISTENT)
if old is PASSIVE_NO_RESULT:
old = self.initialize(state, dict_)
elif old is iterable:
# ignore re-assignment of the current collection, as happens
# implicitly with in-place operators (foo.collection |= other)
return
# place a copy of "old" in state.committed_state
state._modified_event(dict_, self, old, True)
old_collection = getattr(old, '_sa_adapter')
dict_[self.key] = user_data
collections.bulk_replace(new_values, old_collection, new_collection)
old_collection.unlink(old)
def _invalidate_collection(self, collection):
adapter = getattr(collection, '_sa_adapter')
adapter.invalidated = True
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:
collection.append_multiple_without_event(value)
state.dict[self.key] = user_data
state._commit(dict_, [self.key])
if self.key in state._pending_mutations:
# pending items exist. issue a modified event,
# add/remove new items.
state._modified_event(dict_, self, user_data, True)
pending = state._pending_mutations.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')
def backref_listeners(attribute, key, uselist):
"""Apply listeners to synchronize a two-way relationship."""
# use easily recognizable names for stack traces
parent_token = attribute.impl.parent_token
def _acceptable_key_err(child_state, initiator, child_impl):
raise ValueError(
"Bidirectional attribute conflict detected: "
'Passing object %s to attribute "%s" '
'triggers a modify event on attribute "%s" '
'via the backref "%s".' % (
orm_util.state_str(child_state),
initiator.parent_token,
child_impl.parent_token,
attribute.impl.parent_token
)
)
def emit_backref_from_scalar_set_event(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.manager[key].impl
impl.pop(old_state,
old_dict,
state.obj(),
initiator, passive=PASSIVE_NO_FETCH)
if child is not None:
child_state, child_dict = instance_state(child),\
instance_dict(child)
child_impl = child_state.manager[key].impl
if initiator.parent_token is not parent_token and \
initiator.parent_token is not child_impl.parent_token:
_acceptable_key_err(state, initiator, child_impl)
child_impl.append(
child_state,
child_dict,
state.obj(),
initiator,
passive=PASSIVE_NO_FETCH)
return child
def emit_backref_from_collection_append_event(state, child, initiator):
if child is None:
return
child_state, child_dict = instance_state(child), \
instance_dict(child)
child_impl = child_state.manager[key].impl
if initiator.parent_token is not parent_token and \
initiator.parent_token is not child_impl.parent_token:
_acceptable_key_err(state, initiator, child_impl)
child_impl.append(
child_state,
child_dict,
state.obj(),
initiator,
passive=PASSIVE_NO_FETCH)
return child
def emit_backref_from_collection_remove_event(state, child, initiator):
if child is not None:
child_state, child_dict = instance_state(child),\
instance_dict(child)
child_impl = child_state.manager[key].impl
# can't think of a path that would produce an initiator
# mismatch here, as it would require an existing collection
# mismatch.
child_impl.pop(
child_state,
child_dict,
state.obj(),
initiator,
passive=PASSIVE_NO_FETCH)
if uselist:
event.listen(attribute, "append",
emit_backref_from_collection_append_event,
retval=True, raw=True)
else:
event.listen(attribute, "set",
emit_backref_from_scalar_set_event,
retval=True, raw=True)
# TODO: need coverage in test/orm/ of remove event
event.listen(attribute, "remove",
emit_backref_from_collection_remove_event,
retval=True, raw=True)
_NO_HISTORY = util.symbol('NO_HISTORY')
_NO_STATE_SYMBOLS = frozenset([
id(PASSIVE_NO_RESULT),
id(NO_VALUE),
id(NEVER_SET)])
History = util.namedtuple("History", [
"added", "unchanged", "deleted"
])
class History(History):
"""A 3-tuple of added, unchanged and deleted values,
representing the changes which have occurred on an instrumented
attribute.
The easiest way to get a :class:`.History` object for a particular
attribute on an object is to use the :func:`.inspect` function::
from sqlalchemy import inspect
hist = inspect(myobject).attrs.myattribute.history
Each tuple member is an iterable sequence:
* ``added`` - the collection of items added to the attribute (the first
tuple element).
* ``unchanged`` - the collection of items that have not changed on the
attribute (the second tuple element).
* ``deleted`` - the collection of items that have been removed from the
attribute (the third tuple element).
"""
def __nonzero__(self):
return self != HISTORY_BLANK
def empty(self):
"""Return True if this :class:`.History` has no changes
and no existing, unchanged state.
"""
return not bool(
(self.added or self.deleted)
or self.unchanged and self.unchanged != [None]
)
def sum(self):
"""Return a collection of added + unchanged + deleted."""
return (self.added or []) +\
(self.unchanged or []) +\
(self.deleted or [])
def non_deleted(self):
"""Return a collection of added + unchanged."""
return (self.added or []) +\
(self.unchanged or [])
def non_added(self):
"""Return a collection of unchanged + deleted."""
return (self.unchanged or []) +\
(self.deleted or [])
def has_changes(self):
"""Return True if this :class:`.History` has changes."""
return bool(self.added or self.deleted)
def as_state(self):
return History(
[(c is not None)
and instance_state(c) or None
for c in self.added],
[(c is not None)
and instance_state(c) or None
for c in self.unchanged],
[(c is not None)
and instance_state(c) or None
for c in self.deleted],
)
@classmethod
def from_scalar_attribute(cls, attribute, state, current):
original = state.committed_state.get(attribute.key, _NO_HISTORY)
if original is _NO_HISTORY:
if current is NO_VALUE:
return cls((), (), ())
else:
return cls((), [current], ())
# don't let ClauseElement expressions here trip things up
elif attribute.is_equal(current, original) is True:
return cls((), [current], ())
else:
# current convention on native scalars is to not
# include information
# about missing previous value in "deleted", but
# we do include None, which helps in some primary
# key situations
if id(original) in _NO_STATE_SYMBOLS:
deleted = ()
else:
deleted = [original]
if current is NO_VALUE:
return cls((), (), deleted)
else:
return cls([current], (), deleted)
@classmethod
def from_object_attribute(cls, attribute, state, current):
original = state.committed_state.get(attribute.key, _NO_HISTORY)
if original is _NO_HISTORY:
if current is NO_VALUE or current is NEVER_SET:
return cls((), (), ())
else:
return cls((), [current], ())
elif current is original:
return cls((), [current], ())
else:
# current convention on related objects is to not
# include information
# about missing previous value in "deleted", and
# to also not include None - the dependency.py rules
# ignore the None in any case.
if id(original) in _NO_STATE_SYMBOLS or original is None:
deleted = ()
else:
deleted = [original]
if current is NO_VALUE or current is NEVER_SET:
return cls((), (), deleted)
else:
return cls([current], (), deleted)
@classmethod
def from_collection(cls, attribute, state, current):
original = state.committed_state.get(attribute.key, _NO_HISTORY)
if current is NO_VALUE or current is NEVER_SET:
return cls((), (), ())
current = getattr(current, '_sa_adapter')
if original in (NO_VALUE, NEVER_SET):
return cls(list(current), (), ())
elif original is _NO_HISTORY:
return cls((), list(current), ())
else:
current_states = [((c is not None) and instance_state(c)
or None, c)
for c in current
]
original_states = [((c is not None) and instance_state(c)
or None, c)
for c in original
]
current_set = dict(current_states)
original_set = dict(original_states)
return cls(
[o for s, o in current_states if s not in original_set],
[o for s, o in current_states if s in original_set],
[o for s, o in original_states if s not in current_set]
)
HISTORY_BLANK = History(None, None, None)
def get_history(obj, key, passive=PASSIVE_OFF):
"""Return a :class:`.History` record for the given object
and attribute key.
:param obj: an object whose class is instrumented by the
attributes package.
:param key: string attribute name.
:param passive: indicates loading behavior for the attribute
if the value is not already present. This is a
bitflag attribute, which defaults to the symbol
:attr:`.PASSIVE_OFF` indicating all necessary SQL
should be emitted.
"""
if passive is True:
util.warn_deprecated("Passing True for 'passive' is deprecated. "
"Use attributes.PASSIVE_NO_INITIALIZE")
passive = PASSIVE_NO_INITIALIZE
elif passive is False:
util.warn_deprecated("Passing False for 'passive' is "
"deprecated. Use attributes.PASSIVE_OFF")
passive = PASSIVE_OFF
return get_state_history(instance_state(obj), key, passive)
def get_state_history(state, key, passive=PASSIVE_OFF):
return state.get_history(key, passive)
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_attribute(class_, key, **kw):
comparator = kw.pop('comparator', None)
parententity = kw.pop('parententity', None)
doc = kw.pop('doc', None)
desc = register_descriptor(class_, key,
comparator, parententity, doc=doc)
register_attribute_impl(class_, key, **kw)
return desc
def register_attribute_impl(class_, key,
uselist=False, callable_=None,
useobject=False,
impl_class=None, backref=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)
dispatch = manager[key].dispatch
if impl_class:
impl = impl_class(class_, key, typecallable, dispatch, **kw)
elif uselist:
impl = CollectionAttributeImpl(class_, key, callable_, dispatch,
typecallable=typecallable, **kw)
elif useobject:
impl = ScalarObjectAttributeImpl(class_, key, callable_,
dispatch, **kw)
else:
impl = ScalarAttributeImpl(class_, key, callable_, dispatch, **kw)
manager[key].impl = impl
if backref:
backref_listeners(manager[key], backref, uselist)
manager.post_configure_attribute(key)
return manager[key]
def register_descriptor(class_, key, comparator=None,
parententity=None, doc=None):
manager = manager_of_class(class_)
descriptor = InstrumentedAttribute(class_, key, comparator=comparator,
parententity=parententity)
descriptor.__doc__ = doc
manager.instrument_attribute(key, descriptor)
return 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.manager[key].impl
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.manager[key].impl.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.manager[key].impl.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.manager[key].impl.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.manager[key].impl.delete(state, dict_)
def flag_modified(instance, key):
"""Mark an attribute on an instance as 'modified'.
This sets the 'modified' flag on the instance and
establishes an unconditional change event for the given attribute.
"""
state, dict_ = instance_state(instance), instance_dict(instance)
impl = state.manager[key].impl
state._modified_event(dict_, impl, NO_VALUE)