# dynamic.py
# Copyright (C) the SQLAlchemy authors and contributors
#
# 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 sqlalchemy import log,util
from sqlalchemy import exc
from sqlalchemy.orm import exc
from sqlalchemy.sql import operators
from sqlalchemy.orm import (
attributes, object_session, util as mapperutil, strategies, object_mapper
)
from sqlalchemy.orm.query import Query
from sqlalchemy.orm.util import _state_has_identity,has_identity
from sqlalchemy.orm import attributes,collections
class DynaLoader(strategies.AbstractRelationshipLoader):
def init_class_attribute(self, mapper):
self.is_class_level = True
strategies._register_attribute(self,
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
)
def create_row_processor(self, selectcontext, path, mapper, row, adapter):
return (None, None)
log.class_logger(DynaLoader)
class DynamicAttributeImpl(attributes.AttributeImpl):
uses_objects = True
accepts_scalar_loader = False
def __init__(self, class_, key, typecallable,
target_mapper, order_by, query_class=None, **kwargs):
super(DynamicAttributeImpl, self).__init__(class_, key, typecallable, **kwargs)
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=False):
if passive:
return self._get_collection_history(state, passive=True).added_items
else:
return self.query_class(self, state)
def get_collection(self, state, dict_, user_data=None, passive=True):
if passive:
return self._get_collection_history(state, passive=passive).added_items
else:
history = self._get_collection_history(state, passive=passive)
return history.added_items + history.unchanged_items
def fire_append_event(self, state, dict_, value, initiator):
collection_history = self._modified_event(state, dict_)
collection_history.added_items.append(value)
for ext in self.extensions:
ext.append(state, value, initiator or self)
if self.trackparent and value is not None:
self.sethasparent(attributes.instance_state(value), True)
def fire_remove_event(self, state, dict_, value, initiator):
collection_history = self._modified_event(state, dict_)
collection_history.deleted_items.append(value)
if self.trackparent and value is not None:
self.sethasparent(attributes.instance_state(value), False)
for ext in self.extensions:
ext.remove(state, value, initiator or self)
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,
False,
attributes.NEVER_SET,
passive=attributes.PASSIVE_NO_INITIALIZE)
# this is a hack to allow the _base.ComparableEntity fixture
# to work
dict_[self.key] = True
return state.committed_state[self.key]
def set(self, state, dict_, value, initiator, passive=attributes.PASSIVE_OFF):
if initiator is self:
return
self._set_iterable(state, dict_, value)
def _set_iterable(self, state, dict_, iterable, adapter=None):
collection_history = self._modified_event(state, dict_)
new_values = list(iterable)
if _state_has_identity(state):
old_collection = list(self.get(state, dict_))
else:
old_collection = []
collections.bulk_replace(new_values, DynCollectionAdapter(self, state, old_collection), DynCollectionAdapter(self, state, new_values))
def delete(self, *args, **kwargs):
raise NotImplementedError()
def get_history(self, state, dict_, passive=False):
c = self._get_collection_history(state, passive)
return attributes.History(c.added_items, c.unchanged_items, c.deleted_items)
def _get_collection_history(self, state, passive=False):
if self.key in state.committed_state:
c = state.committed_state[self.key]
else:
c = CollectionHistory(self, state)
if not passive:
return CollectionHistory(self, state, apply_to=c)
else:
return c
def append(self, state, dict_, value, initiator, passive=False):
if initiator is not self:
self.fire_append_event(state, dict_, value, initiator)
def remove(self, state, dict_, value, initiator, passive=False):
if initiator is not self:
self.fire_remove_event(state, dict_, value, initiator)
class DynCollectionAdapter(object):
"""the dynamic analogue to orm.collections.CollectionAdapter"""
def __init__(self, attr, owner_state, data):
self.attr = attr
self.state = owner_state
self.data = data
def __iter__(self):
return iter(self.data)
def append_with_event(self, item, initiator=None):
self.attr.append(self.state, self.state.dict, item, initiator)
def remove_with_event(self, item, initiator=None):
self.attr.remove(self.state, self.state.dict, item, initiator)
def append_without_event(self, item):
pass
def remove_without_event(self, item):
pass
class AppenderMixin(object):
query_class = None
def __init__(self, attr, state):
Query.__init__(self, attr.target_mapper, None)
self.instance = instance = state.obj()
self.attr = attr
mapper = object_mapper(instance)
prop = mapper.get_property(self.attr.key, resolve_synonyms=True)
self._criterion = prop.compare(
operators.eq,
instance,
value_is_parent=True,
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 has_identity(self.instance):
return None
else:
return sess
def session(self):
return self.__session()
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),
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_history(
attributes.instance_state(self.instance),
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_history(
attributes.instance_state(self.instance),
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.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" % (
mapperutil.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._order_by = self._order_by
return query
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:
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 = []
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