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"""'dynamic' collection API. returns Query() objects on the 'read' side, alters
a special AttributeHistory on the 'write' side."""
from sqlalchemy import exceptions, util
from sqlalchemy.orm import attributes, object_session, util as mapperutil
from sqlalchemy.orm.query import Query
from sqlalchemy.orm.mapper import has_identity, object_mapper
class DynamicAttributeImpl(attributes.AttributeImpl):
def __init__(self, class_, key, typecallable, target_mapper, **kwargs):
super(DynamicAttributeImpl, self).__init__(class_, key, typecallable, **kwargs)
self.target_mapper = target_mapper
def get(self, state, passive=False):
if passive:
return self._get_collection(state, passive=True).added_items
else:
return AppenderQuery(self, state)
def commit_to_state(self, state, value=attributes.NO_VALUE):
# we have our own AttributeHistory therefore dont need CommittedState
# instead, we reset the history stored on the attribute
state.dict[self.key] = CollectionHistory(self, state)
def get_collection(self, state, user_data=None):
return self._get_collection(state, passive=True).added_items
def set(self, state, value, initiator):
if initiator is self:
return
old_collection = self.get(state).assign(value)
# TODO: emit events ???
state.modified = True
def delete(self, *args, **kwargs):
raise NotImplementedError()
def get_history(self, state, passive=False):
c = self._get_collection(state, passive)
return (c.added_items, c.unchanged_items, c.deleted_items)
def _get_collection(self, state, passive=False):
try:
c = state.dict[self.key]
except KeyError:
state.dict[self.key] = c = CollectionHistory(self, state)
if not passive:
return CollectionHistory(self, state, apply_to=c)
else:
return c
def append(self, state, value, initiator, passive=False):
if initiator is not self:
self._get_collection(state, passive=True).added_items.append(value)
self.fire_append_event(state, value, initiator)
def remove(self, state, value, initiator, passive=False):
if initiator is not self:
self._get_collection(state, passive=True).deleted_items.append(value)
self.fire_remove_event(state, value, initiator)
class AppenderQuery(Query):
def __init__(self, attr, state):
super(AppenderQuery, self).__init__(attr.target_mapper, None)
self.state = state
self.attr = attr
def __session(self):
instance = self.state.obj()
sess = object_session(instance)
if sess is not None and self.autoflush and sess.autoflush and instance in sess:
sess.flush()
if not has_identity(instance):
return None
else:
return sess
def _get_session(self):
return self.__session()
session = property(_get_session)
def __iter__(self):
sess = self.__session()
if sess is None:
return iter(self.attr._get_collection(self.state, passive=True).added_items)
else:
return iter(self._clone(sess))
def __getitem__(self, index):
sess = self.__session()
if sess is None:
return self.attr._get_collection(self.state, passive=True).added_items.__getitem__(index)
else:
return self._clone(sess).__getitem__(index)
def count(self):
sess = self.__session()
if sess is None:
return len(self.attr._get_collection(self.state, passive=True).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.state.obj()
if sess is None:
sess = object_session(instance)
if sess is None:
try:
sess = object_mapper(instance).get_session()
except exceptions.InvalidRequestError:
raise exceptions.InvalidRequestError("Parent instance %s is not bound to a Session, and no contextual session is established; lazy load operation of attribute '%s' cannot proceed" % (mapperutil.instance_str(instance), self.attr.key))
return sess.query(self.attr.target_mapper).with_parent(instance)
def assign(self, collection):
instance = self.state.obj()
if has_identity(instance):
oldlist = list(self)
else:
oldlist = []
self.attr._get_collection(self.state, passive=True).replace(oldlist, collection)
return oldlist
def append(self, item):
self.attr.append(self.state, item, None)
def remove(self, item):
self.attr.remove(self.state, item, None)
class CollectionHistory(object):
"""Overrides AttributeHistory to receive append/remove events directly."""
def __init__(self, attr, state, apply_to=None):
if apply_to:
deleted = util.IdentitySet(apply_to.deleted_items)
added = apply_to.added_items
coll = AppenderQuery(attr, state).autoflush(False)
self.unchanged_items = [o for o in util.IdentitySet(coll) if o not in deleted]
self.added_items = apply_to.added_items
self.deleted_items = apply_to.deleted_items
else:
self.deleted_items = []
self.added_items = []
self.unchanged_items = []
def replace(self, olditems, newitems):
self.added_items = newitems
self.deleted_items = olditems
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