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# orm/dynamic.py
# Copyright (C) 2005-2021 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
"""Dynamic collection API.
Dynamic collections act like Query() objects for read operations and support
basic add/delete mutation.
"""
from . import attributes
from . import exc as orm_exc
from . import interfaces
from . import object_mapper
from . import object_session
from . import properties
from . import strategies
from . import util as orm_util
from .query import Query
from .. import exc
from .. import log
from .. import util
@log.class_logger
@properties.RelationshipProperty.strategy_for(lazy="dynamic")
class DynaLoader(strategies.AbstractRelationshipLoader):
def init_class_attribute(self, mapper):
self.is_class_level = True
if not self.uselist:
raise exc.InvalidRequestError(
"On relationship %s, 'dynamic' loaders cannot be used with "
"many-to-one/one-to-one relationships and/or "
"uselist=False." % self.parent_property
)
elif self.parent_property.direction not in (
interfaces.ONETOMANY,
interfaces.MANYTOMANY,
):
util.warn(
"On relationship %s, 'dynamic' loaders cannot be used with "
"many-to-one/one-to-one relationships and/or "
"uselist=False. This warning will be an exception in a "
"future release." % self.parent_property
)
strategies._register_attribute(
self.parent_property,
mapper,
useobject=True,
impl_class=DynamicAttributeImpl,
target_mapper=self.parent_property.mapper,
order_by=self.parent_property.order_by,
query_class=self.parent_property.query_class,
)
class DynamicAttributeImpl(attributes.AttributeImpl):
uses_objects = True
default_accepts_scalar_loader = False
supports_population = False
collection = False
dynamic = True
def __init__(
self,
class_,
key,
typecallable,
dispatch,
target_mapper,
order_by,
query_class=None,
**kw
):
super(DynamicAttributeImpl, self).__init__(
class_, key, typecallable, dispatch, **kw
)
self.target_mapper = target_mapper
self.order_by = order_by
if not query_class:
self.query_class = AppenderQuery
elif AppenderMixin in query_class.mro():
self.query_class = query_class
else:
self.query_class = mixin_user_query(query_class)
def get(self, state, dict_, passive=attributes.PASSIVE_OFF):
if not passive & attributes.SQL_OK:
return self._get_collection_history(
state, attributes.PASSIVE_NO_INITIALIZE
).added_items
else:
return self.query_class(self, state)
def get_collection(
self,
state,
dict_,
user_data=None,
passive=attributes.PASSIVE_NO_INITIALIZE,
):
if not passive & attributes.SQL_OK:
return self._get_collection_history(state, passive).added_items
else:
history = self._get_collection_history(state, passive)
return history.added_plus_unchanged
@util.memoized_property
def _append_token(self):
return attributes.Event(self, attributes.OP_APPEND)
@util.memoized_property
def _remove_token(self):
return attributes.Event(self, attributes.OP_REMOVE)
def fire_append_event(
self, state, dict_, value, initiator, collection_history=None
):
if collection_history is None:
collection_history = self._modified_event(state, dict_)
collection_history.add_added(value)
for fn in self.dispatch.append:
value = fn(state, value, initiator or self._append_token)
if self.trackparent and value is not None:
self.sethasparent(attributes.instance_state(value), state, True)
def fire_remove_event(
self, state, dict_, value, initiator, collection_history=None
):
if collection_history is None:
collection_history = self._modified_event(state, dict_)
collection_history.add_removed(value)
if self.trackparent and value is not None:
self.sethasparent(attributes.instance_state(value), state, False)
for fn in self.dispatch.remove:
fn(state, value, initiator or self._remove_token)
def _modified_event(self, state, dict_):
if self.key not in state.committed_state:
state.committed_state[self.key] = CollectionHistory(self, state)
state._modified_event(dict_, self, attributes.NEVER_SET)
# this is a hack to allow the fixtures.ComparableEntity fixture
# to work
dict_[self.key] = True
return state.committed_state[self.key]
def set(
self,
state,
dict_,
value,
initiator=None,
passive=attributes.PASSIVE_OFF,
check_old=None,
pop=False,
_adapt=True,
):
if initiator and initiator.parent_token is self.parent_token:
return
if pop and value is None:
return
iterable = value
new_values = list(iterable)
if state.has_identity:
old_collection = util.IdentitySet(self.get(state, dict_))
collection_history = self._modified_event(state, dict_)
if not state.has_identity:
old_collection = collection_history.added_items
else:
old_collection = old_collection.union(
collection_history.added_items
)
idset = util.IdentitySet
constants = old_collection.intersection(new_values)
additions = idset(new_values).difference(constants)
removals = old_collection.difference(constants)
for member in new_values:
if member in additions:
self.fire_append_event(
state,
dict_,
member,
None,
collection_history=collection_history,
)
for member in removals:
self.fire_remove_event(
state,
dict_,
member,
None,
collection_history=collection_history,
)
def delete(self, *args, **kwargs):
raise NotImplementedError()
def set_committed_value(self, state, dict_, value):
raise NotImplementedError(
"Dynamic attributes don't support " "collection population."
)
def get_history(self, state, dict_, passive=attributes.PASSIVE_OFF):
c = self._get_collection_history(state, passive)
return c.as_history()
def get_all_pending(
self, state, dict_, passive=attributes.PASSIVE_NO_INITIALIZE
):
c = self._get_collection_history(state, passive)
return [(attributes.instance_state(x), x) for x in c.all_items]
def _get_collection_history(self, state, passive=attributes.PASSIVE_OFF):
if self.key in state.committed_state:
c = state.committed_state[self.key]
else:
c = CollectionHistory(self, state)
if state.has_identity and (passive & attributes.INIT_OK):
return CollectionHistory(self, state, apply_to=c)
else:
return c
def append(
self, state, dict_, value, initiator, passive=attributes.PASSIVE_OFF
):
if initiator is not self:
self.fire_append_event(state, dict_, value, initiator)
def remove(
self, state, dict_, value, initiator, passive=attributes.PASSIVE_OFF
):
if initiator is not self:
self.fire_remove_event(state, dict_, value, initiator)
def pop(
self, state, dict_, value, initiator, passive=attributes.PASSIVE_OFF
):
self.remove(state, dict_, value, initiator, passive=passive)
class AppenderMixin(object):
query_class = None
def __init__(self, attr, state):
super(AppenderMixin, self).__init__(attr.target_mapper, None)
self.instance = instance = state.obj()
self.attr = attr
mapper = object_mapper(instance)
prop = mapper._props[self.attr.key]
if prop.secondary is not None:
# this is a hack right now. The Query only knows how to
# make subsequent joins() without a given left-hand side
# from self._from_obj[0]. We need to ensure prop.secondary
# is in the FROM. So we purposely put the mapper selectable
# in _from_obj[0] to ensure a user-defined join() later on
# doesn't fail, and secondary is then in _from_obj[1].
self._from_obj = (prop.mapper.selectable, prop.secondary)
self._criterion = prop._with_parent(instance, alias_secondary=False)
if self.attr.order_by:
self._order_by = self.attr.order_by
def session(self):
sess = object_session(self.instance)
if (
sess is not None
and self.autoflush
and sess.autoflush
and self.instance in sess
):
sess.flush()
if not orm_util.has_identity(self.instance):
return None
else:
return sess
session = property(session, lambda s, x: None)
def __iter__(self):
sess = self.session
if sess is None:
return iter(
self.attr._get_collection_history(
attributes.instance_state(self.instance),
attributes.PASSIVE_NO_INITIALIZE,
).added_items
)
else:
return iter(self._clone(sess))
def __getitem__(self, index):
sess = self.session
if sess is None:
return self.attr._get_collection_history(
attributes.instance_state(self.instance),
attributes.PASSIVE_NO_INITIALIZE,
).indexed(index)
else:
return self._clone(sess).__getitem__(index)
def count(self):
sess = self.session
if sess is None:
return len(
self.attr._get_collection_history(
attributes.instance_state(self.instance),
attributes.PASSIVE_NO_INITIALIZE,
).added_items
)
else:
return self._clone(sess).count()
def _clone(self, sess=None):
# note we're returning an entirely new Query class instance
# here without any assignment capabilities; the class of this
# query is determined by the session.
instance = self.instance
if sess is None:
sess = object_session(instance)
if sess is None:
raise orm_exc.DetachedInstanceError(
"Parent instance %s is not bound to a Session, and no "
"contextual session is established; lazy load operation "
"of attribute '%s' cannot proceed"
% (orm_util.instance_str(instance), self.attr.key)
)
if self.query_class:
query = self.query_class(self.attr.target_mapper, session=sess)
else:
query = sess.query(self.attr.target_mapper)
query._criterion = self._criterion
query._from_obj = self._from_obj
query._order_by = self._order_by
return query
def extend(self, iterator):
for item in iterator:
self.attr.append(
attributes.instance_state(self.instance),
attributes.instance_dict(self.instance),
item,
None,
)
def append(self, item):
self.attr.append(
attributes.instance_state(self.instance),
attributes.instance_dict(self.instance),
item,
None,
)
def remove(self, item):
self.attr.remove(
attributes.instance_state(self.instance),
attributes.instance_dict(self.instance),
item,
None,
)
class AppenderQuery(AppenderMixin, Query):
"""A dynamic query that supports basic collection storage operations."""
def mixin_user_query(cls):
"""Return a new class with AppenderQuery functionality layered over."""
name = "Appender" + cls.__name__
return type(name, (AppenderMixin, cls), {"query_class": cls})
class CollectionHistory(object):
"""Overrides AttributeHistory to receive append/remove events directly."""
def __init__(self, attr, state, apply_to=None):
if apply_to:
coll = AppenderQuery(attr, state).autoflush(False)
self.unchanged_items = util.OrderedIdentitySet(coll)
self.added_items = apply_to.added_items
self.deleted_items = apply_to.deleted_items
self._reconcile_collection = True
else:
self.deleted_items = util.OrderedIdentitySet()
self.added_items = util.OrderedIdentitySet()
self.unchanged_items = util.OrderedIdentitySet()
self._reconcile_collection = False
@property
def added_plus_unchanged(self):
return list(self.added_items.union(self.unchanged_items))
@property
def all_items(self):
return list(
self.added_items.union(self.unchanged_items).union(
self.deleted_items
)
)
def as_history(self):
if self._reconcile_collection:
added = self.added_items.difference(self.unchanged_items)
deleted = self.deleted_items.intersection(self.unchanged_items)
unchanged = self.unchanged_items.difference(deleted)
else:
added, unchanged, deleted = (
self.added_items,
self.unchanged_items,
self.deleted_items,
)
return attributes.History(list(added), list(unchanged), list(deleted))
def indexed(self, index):
return list(self.added_items)[index]
def add_added(self, value):
self.added_items.add(value)
def add_removed(self, value):
if value in self.added_items:
self.added_items.remove(value)
else:
self.deleted_items.add(value)