294 lines
10 KiB
Python
294 lines
10 KiB
Python
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# dynamic.py
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# Copyright (C) the SQLAlchemy authors and contributors
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#
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# This module is part of SQLAlchemy and is released under
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# the MIT License: http://www.opensource.org/licenses/mit-license.php
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"""Dynamic collection API.
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Dynamic collections act like Query() objects for read operations and support
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basic add/delete mutation.
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"""
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from sqlalchemy import log, util
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from sqlalchemy import exc as sa_exc
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from sqlalchemy.orm import exc as sa_exc
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from sqlalchemy.sql import operators
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from sqlalchemy.orm import (
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attributes, object_session, util as mapperutil, strategies, object_mapper
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)
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from sqlalchemy.orm.query import Query
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from sqlalchemy.orm.util import _state_has_identity, has_identity
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from sqlalchemy.orm import attributes, collections
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class DynaLoader(strategies.AbstractRelationshipLoader):
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def init_class_attribute(self, mapper):
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self.is_class_level = True
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strategies._register_attribute(self,
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mapper,
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useobject=True,
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impl_class=DynamicAttributeImpl,
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target_mapper=self.parent_property.mapper,
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order_by=self.parent_property.order_by,
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query_class=self.parent_property.query_class
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)
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def create_row_processor(self, selectcontext, path, mapper, row, adapter):
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return (None, None)
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log.class_logger(DynaLoader)
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class DynamicAttributeImpl(attributes.AttributeImpl):
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uses_objects = True
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accepts_scalar_loader = False
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def __init__(self, class_, key, typecallable,
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target_mapper, order_by, query_class=None, **kwargs):
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super(DynamicAttributeImpl, self).__init__(class_, key, typecallable, **kwargs)
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self.target_mapper = target_mapper
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self.order_by = order_by
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if not query_class:
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self.query_class = AppenderQuery
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elif AppenderMixin in query_class.mro():
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self.query_class = query_class
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else:
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self.query_class = mixin_user_query(query_class)
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def get(self, state, dict_, passive=False):
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if passive:
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return self._get_collection_history(state, passive=True).added_items
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else:
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return self.query_class(self, state)
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def get_collection(self, state, dict_, user_data=None, passive=True):
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if passive:
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return self._get_collection_history(state, passive=passive).added_items
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else:
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history = self._get_collection_history(state, passive=passive)
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return history.added_items + history.unchanged_items
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def fire_append_event(self, state, dict_, value, initiator):
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collection_history = self._modified_event(state, dict_)
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collection_history.added_items.append(value)
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for ext in self.extensions:
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ext.append(state, value, initiator or self)
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if self.trackparent and value is not None:
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self.sethasparent(attributes.instance_state(value), True)
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def fire_remove_event(self, state, dict_, value, initiator):
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collection_history = self._modified_event(state, dict_)
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collection_history.deleted_items.append(value)
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if self.trackparent and value is not None:
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self.sethasparent(attributes.instance_state(value), False)
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for ext in self.extensions:
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ext.remove(state, value, initiator or self)
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def _modified_event(self, state, dict_):
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if self.key not in state.committed_state:
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state.committed_state[self.key] = CollectionHistory(self, state)
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state.modified_event(dict_,
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self,
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False,
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attributes.NEVER_SET,
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passive=attributes.PASSIVE_NO_INITIALIZE)
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# this is a hack to allow the _base.ComparableEntity fixture
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# to work
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dict_[self.key] = True
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return state.committed_state[self.key]
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def set(self, state, dict_, value, initiator, passive=attributes.PASSIVE_OFF):
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if initiator is self:
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return
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self._set_iterable(state, dict_, value)
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def _set_iterable(self, state, dict_, iterable, adapter=None):
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collection_history = self._modified_event(state, dict_)
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new_values = list(iterable)
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if _state_has_identity(state):
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old_collection = list(self.get(state, dict_))
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else:
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old_collection = []
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collections.bulk_replace(new_values, DynCollectionAdapter(self, state, old_collection), DynCollectionAdapter(self, state, new_values))
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def delete(self, *args, **kwargs):
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raise NotImplementedError()
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def get_history(self, state, dict_, passive=False):
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c = self._get_collection_history(state, passive)
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return attributes.History(c.added_items, c.unchanged_items, c.deleted_items)
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def _get_collection_history(self, state, passive=False):
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if self.key in state.committed_state:
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c = state.committed_state[self.key]
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else:
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c = CollectionHistory(self, state)
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if not passive:
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return CollectionHistory(self, state, apply_to=c)
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else:
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return c
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def append(self, state, dict_, value, initiator, passive=False):
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if initiator is not self:
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self.fire_append_event(state, dict_, value, initiator)
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def remove(self, state, dict_, value, initiator, passive=False):
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if initiator is not self:
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self.fire_remove_event(state, dict_, value, initiator)
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class DynCollectionAdapter(object):
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"""the dynamic analogue to orm.collections.CollectionAdapter"""
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def __init__(self, attr, owner_state, data):
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self.attr = attr
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self.state = owner_state
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self.data = data
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def __iter__(self):
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return iter(self.data)
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def append_with_event(self, item, initiator=None):
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self.attr.append(self.state, self.state.dict, item, initiator)
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def remove_with_event(self, item, initiator=None):
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self.attr.remove(self.state, self.state.dict, item, initiator)
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def append_without_event(self, item):
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pass
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def remove_without_event(self, item):
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pass
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class AppenderMixin(object):
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query_class = None
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def __init__(self, attr, state):
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Query.__init__(self, attr.target_mapper, None)
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self.instance = instance = state.obj()
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self.attr = attr
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mapper = object_mapper(instance)
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prop = mapper.get_property(self.attr.key, resolve_synonyms=True)
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self._criterion = prop.compare(
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operators.eq,
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instance,
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value_is_parent=True,
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alias_secondary=False)
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if self.attr.order_by:
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self._order_by = self.attr.order_by
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def __session(self):
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sess = object_session(self.instance)
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if sess is not None and self.autoflush and sess.autoflush and self.instance in sess:
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sess.flush()
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if not has_identity(self.instance):
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return None
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else:
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return sess
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def session(self):
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return self.__session()
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session = property(session, lambda s, x:None)
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def __iter__(self):
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sess = self.__session()
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if sess is None:
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return iter(self.attr._get_collection_history(
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attributes.instance_state(self.instance),
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passive=True).added_items)
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else:
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return iter(self._clone(sess))
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def __getitem__(self, index):
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sess = self.__session()
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if sess is None:
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return self.attr._get_collection_history(
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attributes.instance_state(self.instance),
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passive=True).added_items.__getitem__(index)
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else:
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return self._clone(sess).__getitem__(index)
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def count(self):
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sess = self.__session()
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if sess is None:
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return len(self.attr._get_collection_history(
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attributes.instance_state(self.instance),
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passive=True).added_items)
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else:
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return self._clone(sess).count()
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def _clone(self, sess=None):
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# note we're returning an entirely new Query class instance
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# here without any assignment capabilities; the class of this
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# query is determined by the session.
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instance = self.instance
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if sess is None:
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sess = object_session(instance)
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if sess is None:
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raise orm_exc.DetachedInstanceError(
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"Parent instance %s is not bound to a Session, and no "
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"contextual session is established; lazy load operation "
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"of attribute '%s' cannot proceed" % (
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mapperutil.instance_str(instance), self.attr.key))
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if self.query_class:
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query = self.query_class(self.attr.target_mapper, session=sess)
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else:
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query = sess.query(self.attr.target_mapper)
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query._criterion = self._criterion
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query._order_by = self._order_by
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return query
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def append(self, item):
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self.attr.append(
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attributes.instance_state(self.instance),
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attributes.instance_dict(self.instance), item, None)
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def remove(self, item):
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self.attr.remove(
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attributes.instance_state(self.instance),
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attributes.instance_dict(self.instance), item, None)
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class AppenderQuery(AppenderMixin, Query):
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"""A dynamic query that supports basic collection storage operations."""
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def mixin_user_query(cls):
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"""Return a new class with AppenderQuery functionality layered over."""
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name = 'Appender' + cls.__name__
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return type(name, (AppenderMixin, cls), {'query_class': cls})
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class CollectionHistory(object):
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"""Overrides AttributeHistory to receive append/remove events directly."""
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def __init__(self, attr, state, apply_to=None):
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if apply_to:
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deleted = util.IdentitySet(apply_to.deleted_items)
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added = apply_to.added_items
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coll = AppenderQuery(attr, state).autoflush(False)
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self.unchanged_items = [o for o in util.IdentitySet(coll) if o not in deleted]
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self.added_items = apply_to.added_items
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self.deleted_items = apply_to.deleted_items
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else:
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self.deleted_items = []
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self.added_items = []
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self.unchanged_items = []
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