first add files

1 files changed, 1290 insertions, 0 deletions

diff --git a/lib/sqlalchemy/orm/dependency.py b/lib/sqlalchemy/orm/dependency.py
new file mode 100644
index 0000000..1b5be9a
--- /dev/null
+++ b/lib/sqlalchemy/orm/dependency.py
@@ -0,0 +1,1290 @@
+# orm/dependency.py
+# Copyright (C) 2005-2022 the SQLAlchemy authors and contributors
+# <see AUTHORS file>
+#
+# This module is part of SQLAlchemy and is released under
+# the MIT License: https://www.opensource.org/licenses/mit-license.php
+
+"""Relationship dependencies.
+
+"""
+
+from . import attributes
+from . import exc
+from . import sync
+from . import unitofwork
+from . import util as mapperutil
+from .interfaces import MANYTOMANY
+from .interfaces import MANYTOONE
+from .interfaces import ONETOMANY
+from .. import exc as sa_exc
+from .. import sql
+from .. import util
+
+
+class DependencyProcessor(object):
+    def __init__(self, prop):
+        self.prop = prop
+        self.cascade = prop.cascade
+        self.mapper = prop.mapper
+        self.parent = prop.parent
+        self.secondary = prop.secondary
+        self.direction = prop.direction
+        self.post_update = prop.post_update
+        self.passive_deletes = prop.passive_deletes
+        self.passive_updates = prop.passive_updates
+        self.enable_typechecks = prop.enable_typechecks
+        if self.passive_deletes:
+            self._passive_delete_flag = attributes.PASSIVE_NO_INITIALIZE
+        else:
+            self._passive_delete_flag = attributes.PASSIVE_OFF
+        if self.passive_updates:
+            self._passive_update_flag = attributes.PASSIVE_NO_INITIALIZE
+        else:
+            self._passive_update_flag = attributes.PASSIVE_OFF
+
+        self.sort_key = "%s_%s" % (self.parent._sort_key, prop.key)
+        self.key = prop.key
+        if not self.prop.synchronize_pairs:
+            raise sa_exc.ArgumentError(
+                "Can't build a DependencyProcessor for relationship %s. "
+                "No target attributes to populate between parent and "
+                "child are present" % self.prop
+            )
+
+    @classmethod
+    def from_relationship(cls, prop):
+        return _direction_to_processor[prop.direction](prop)
+
+    def hasparent(self, state):
+        """return True if the given object instance has a parent,
+        according to the ``InstrumentedAttribute`` handled by this
+        ``DependencyProcessor``.
+
+        """
+        return self.parent.class_manager.get_impl(self.key).hasparent(state)
+
+    def per_property_preprocessors(self, uow):
+        """establish actions and dependencies related to a flush.
+
+        These actions will operate on all relevant states in
+        the aggregate.
+
+        """
+        uow.register_preprocessor(self, True)
+
+    def per_property_flush_actions(self, uow):
+        after_save = unitofwork.ProcessAll(uow, self, False, True)
+        before_delete = unitofwork.ProcessAll(uow, self, True, True)
+
+        parent_saves = unitofwork.SaveUpdateAll(
+            uow, self.parent.primary_base_mapper
+        )
+        child_saves = unitofwork.SaveUpdateAll(
+            uow, self.mapper.primary_base_mapper
+        )
+
+        parent_deletes = unitofwork.DeleteAll(
+            uow, self.parent.primary_base_mapper
+        )
+        child_deletes = unitofwork.DeleteAll(
+            uow, self.mapper.primary_base_mapper
+        )
+
+        self.per_property_dependencies(
+            uow,
+            parent_saves,
+            child_saves,
+            parent_deletes,
+            child_deletes,
+            after_save,
+            before_delete,
+        )
+
+    def per_state_flush_actions(self, uow, states, isdelete):
+        """establish actions and dependencies related to a flush.
+
+        These actions will operate on all relevant states
+        individually.    This occurs only if there are cycles
+        in the 'aggregated' version of events.
+
+        """
+
+        child_base_mapper = self.mapper.primary_base_mapper
+        child_saves = unitofwork.SaveUpdateAll(uow, child_base_mapper)
+        child_deletes = unitofwork.DeleteAll(uow, child_base_mapper)
+
+        # locate and disable the aggregate processors
+        # for this dependency
+
+        if isdelete:
+            before_delete = unitofwork.ProcessAll(uow, self, True, True)
+            before_delete.disabled = True
+        else:
+            after_save = unitofwork.ProcessAll(uow, self, False, True)
+            after_save.disabled = True
+
+        # check if the "child" side is part of the cycle
+
+        if child_saves not in uow.cycles:
+            # based on the current dependencies we use, the saves/
+            # deletes should always be in the 'cycles' collection
+            # together.   if this changes, we will have to break up
+            # this method a bit more.
+            assert child_deletes not in uow.cycles
+
+            # child side is not part of the cycle, so we will link per-state
+            # actions to the aggregate "saves", "deletes" actions
+            child_actions = [(child_saves, False), (child_deletes, True)]
+            child_in_cycles = False
+        else:
+            child_in_cycles = True
+
+        # check if the "parent" side is part of the cycle
+        if not isdelete:
+            parent_saves = unitofwork.SaveUpdateAll(
+                uow, self.parent.base_mapper
+            )
+            parent_deletes = before_delete = None
+            if parent_saves in uow.cycles:
+                parent_in_cycles = True
+        else:
+            parent_deletes = unitofwork.DeleteAll(uow, self.parent.base_mapper)
+            parent_saves = after_save = None
+            if parent_deletes in uow.cycles:
+                parent_in_cycles = True
+
+        # now create actions /dependencies for each state.
+
+        for state in states:
+            # detect if there's anything changed or loaded
+            # by a preprocessor on this state/attribute.   In the
+            # case of deletes we may try to load missing items here as well.
+            sum_ = state.manager[self.key].impl.get_all_pending(
+                state,
+                state.dict,
+                self._passive_delete_flag
+                if isdelete
+                else attributes.PASSIVE_NO_INITIALIZE,
+            )
+
+            if not sum_:
+                continue
+
+            if isdelete:
+                before_delete = unitofwork.ProcessState(uow, self, True, state)
+                if parent_in_cycles:
+                    parent_deletes = unitofwork.DeleteState(uow, state)
+            else:
+                after_save = unitofwork.ProcessState(uow, self, False, state)
+                if parent_in_cycles:
+                    parent_saves = unitofwork.SaveUpdateState(uow, state)
+
+            if child_in_cycles:
+                child_actions = []
+                for child_state, child in sum_:
+                    if child_state not in uow.states:
+                        child_action = (None, None)
+                    else:
+                        (deleted, listonly) = uow.states[child_state]
+                        if deleted:
+                            child_action = (
+                                unitofwork.DeleteState(uow, child_state),
+                                True,
+                            )
+                        else:
+                            child_action = (
+                                unitofwork.SaveUpdateState(uow, child_state),
+                                False,
+                            )
+                    child_actions.append(child_action)
+
+            # establish dependencies between our possibly per-state
+            # parent action and our possibly per-state child action.
+            for child_action, childisdelete in child_actions:
+                self.per_state_dependencies(
+                    uow,
+                    parent_saves,
+                    parent_deletes,
+                    child_action,
+                    after_save,
+                    before_delete,
+                    isdelete,
+                    childisdelete,
+                )
+
+    def presort_deletes(self, uowcommit, states):
+        return False
+
+    def presort_saves(self, uowcommit, states):
+        return False
+
+    def process_deletes(self, uowcommit, states):
+        pass
+
+    def process_saves(self, uowcommit, states):
+        pass
+
+    def prop_has_changes(self, uowcommit, states, isdelete):
+        if not isdelete or self.passive_deletes:
+            passive = attributes.PASSIVE_NO_INITIALIZE
+        elif self.direction is MANYTOONE:
+            # here, we were hoping to optimize having to fetch many-to-one
+            # for history and ignore it, if there's no further cascades
+            # to take place.  however there are too many less common conditions
+            # that still take place and tests in test_relationships /
+            # test_cascade etc. will still fail.
+            passive = attributes.PASSIVE_NO_FETCH_RELATED
+        else:
+            passive = attributes.PASSIVE_OFF
+
+        for s in states:
+            # TODO: add a high speed method
+            # to InstanceState which returns:  attribute
+            # has a non-None value, or had one
+            history = uowcommit.get_attribute_history(s, self.key, passive)
+            if history and not history.empty():
+                return True
+        else:
+            return (
+                states
+                and not self.prop._is_self_referential
+                and self.mapper in uowcommit.mappers
+            )
+
+    def _verify_canload(self, state):
+        if self.prop.uselist and state is None:
+            raise exc.FlushError(
+                "Can't flush None value found in "
+                "collection %s" % (self.prop,)
+            )
+        elif state is not None and not self.mapper._canload(
+            state, allow_subtypes=not self.enable_typechecks
+        ):
+            if self.mapper._canload(state, allow_subtypes=True):
+                raise exc.FlushError(
+                    "Attempting to flush an item of type "
+                    "%(x)s as a member of collection "
+                    '"%(y)s". Expected an object of type '
+                    "%(z)s or a polymorphic subclass of "
+                    "this type. If %(x)s is a subclass of "
+                    '%(z)s, configure mapper "%(zm)s" to '
+                    "load this subtype polymorphically, or "
+                    "set enable_typechecks=False to allow "
+                    "any subtype to be accepted for flush. "
+                    % {
+                        "x": state.class_,
+                        "y": self.prop,
+                        "z": self.mapper.class_,
+                        "zm": self.mapper,
+                    }
+                )
+            else:
+                raise exc.FlushError(
+                    "Attempting to flush an item of type "
+                    "%(x)s as a member of collection "
+                    '"%(y)s". Expected an object of type '
+                    "%(z)s or a polymorphic subclass of "
+                    "this type."
+                    % {
+                        "x": state.class_,
+                        "y": self.prop,
+                        "z": self.mapper.class_,
+                    }
+                )
+
+    def _synchronize(self, state, child, associationrow, clearkeys, uowcommit):
+        raise NotImplementedError()
+
+    def _get_reversed_processed_set(self, uow):
+        if not self.prop._reverse_property:
+            return None
+
+        process_key = tuple(
+            sorted([self.key] + [p.key for p in self.prop._reverse_property])
+        )
+        return uow.memo(("reverse_key", process_key), set)
+
+    def _post_update(self, state, uowcommit, related, is_m2o_delete=False):
+        for x in related:
+            if not is_m2o_delete or x is not None:
+                uowcommit.register_post_update(
+                    state, [r for l, r in self.prop.synchronize_pairs]
+                )
+                break
+
+    def _pks_changed(self, uowcommit, state):
+        raise NotImplementedError()
+
+    def __repr__(self):
+        return "%s(%s)" % (self.__class__.__name__, self.prop)
+
+
+class OneToManyDP(DependencyProcessor):
+    def per_property_dependencies(
+        self,
+        uow,
+        parent_saves,
+        child_saves,
+        parent_deletes,
+        child_deletes,
+        after_save,
+        before_delete,
+    ):
+        if self.post_update:
+            child_post_updates = unitofwork.PostUpdateAll(
+                uow, self.mapper.primary_base_mapper, False
+            )
+            child_pre_updates = unitofwork.PostUpdateAll(
+                uow, self.mapper.primary_base_mapper, True
+            )
+
+            uow.dependencies.update(
+                [
+                    (child_saves, after_save),
+                    (parent_saves, after_save),
+                    (after_save, child_post_updates),
+                    (before_delete, child_pre_updates),
+                    (child_pre_updates, parent_deletes),
+                    (child_pre_updates, child_deletes),
+                ]
+            )
+        else:
+            uow.dependencies.update(
+                [
+                    (parent_saves, after_save),
+                    (after_save, child_saves),
+                    (after_save, child_deletes),
+                    (child_saves, parent_deletes),
+                    (child_deletes, parent_deletes),
+                    (before_delete, child_saves),
+                    (before_delete, child_deletes),
+                ]
+            )
+
+    def per_state_dependencies(
+        self,
+        uow,
+        save_parent,
+        delete_parent,
+        child_action,
+        after_save,
+        before_delete,
+        isdelete,
+        childisdelete,
+    ):
+
+        if self.post_update:
+
+            child_post_updates = unitofwork.PostUpdateAll(
+                uow, self.mapper.primary_base_mapper, False
+            )
+            child_pre_updates = unitofwork.PostUpdateAll(
+                uow, self.mapper.primary_base_mapper, True
+            )
+
+            # TODO: this whole block is not covered
+            # by any tests
+            if not isdelete:
+                if childisdelete:
+                    uow.dependencies.update(
+                        [
+                            (child_action, after_save),
+                            (after_save, child_post_updates),
+                        ]
+                    )
+                else:
+                    uow.dependencies.update(
+                        [
+                            (save_parent, after_save),
+                            (child_action, after_save),
+                            (after_save, child_post_updates),
+                        ]
+                    )
+            else:
+                if childisdelete:
+                    uow.dependencies.update(
+                        [
+                            (before_delete, child_pre_updates),
+                            (child_pre_updates, delete_parent),
+                        ]
+                    )
+                else:
+                    uow.dependencies.update(
+                        [
+                            (before_delete, child_pre_updates),
+                            (child_pre_updates, delete_parent),
+                        ]
+                    )
+        elif not isdelete:
+            uow.dependencies.update(
+                [
+                    (save_parent, after_save),
+                    (after_save, child_action),
+                    (save_parent, child_action),
+                ]
+            )
+        else:
+            uow.dependencies.update(
+                [(before_delete, child_action), (child_action, delete_parent)]
+            )
+
+    def presort_deletes(self, uowcommit, states):
+        # head object is being deleted, and we manage its list of
+        # child objects the child objects have to have their
+        # foreign key to the parent set to NULL
+        should_null_fks = (
+            not self.cascade.delete and not self.passive_deletes == "all"
+        )
+
+        for state in states:
+            history = uowcommit.get_attribute_history(
+                state, self.key, self._passive_delete_flag
+            )
+            if history:
+                for child in history.deleted:
+                    if child is not None and self.hasparent(child) is False:
+                        if self.cascade.delete_orphan:
+                            uowcommit.register_object(child, isdelete=True)
+                        else:
+                            uowcommit.register_object(child)
+
+                if should_null_fks:
+                    for child in history.unchanged:
+                        if child is not None:
+                            uowcommit.register_object(
+                                child, operation="delete", prop=self.prop
+                            )
+
+    def presort_saves(self, uowcommit, states):
+        children_added = uowcommit.memo(("children_added", self), set)
+
+        should_null_fks = (
+            not self.cascade.delete_orphan
+            and not self.passive_deletes == "all"
+        )
+
+        for state in states:
+            pks_changed = self._pks_changed(uowcommit, state)
+
+            if not pks_changed or self.passive_updates:
+                passive = attributes.PASSIVE_NO_INITIALIZE
+            else:
+                passive = attributes.PASSIVE_OFF
+
+            history = uowcommit.get_attribute_history(state, self.key, passive)
+            if history:
+                for child in history.added:
+                    if child is not None:
+                        uowcommit.register_object(
+                            child,
+                            cancel_delete=True,
+                            operation="add",
+                            prop=self.prop,
+                        )
+
+                children_added.update(history.added)
+
+                for child in history.deleted:
+                    if not self.cascade.delete_orphan:
+                        if should_null_fks:
+                            uowcommit.register_object(
+                                child,
+                                isdelete=False,
+                                operation="delete",
+                                prop=self.prop,
+                            )
+                    elif self.hasparent(child) is False:
+                        uowcommit.register_object(
+                            child,
+                            isdelete=True,
+                            operation="delete",
+                            prop=self.prop,
+                        )
+                        for c, m, st_, dct_ in self.mapper.cascade_iterator(
+                            "delete", child
+                        ):
+                            uowcommit.register_object(st_, isdelete=True)
+
+            if pks_changed:
+                if history:
+                    for child in history.unchanged:
+                        if child is not None:
+                            uowcommit.register_object(
+                                child,
+                                False,
+                                self.passive_updates,
+                                operation="pk change",
+                                prop=self.prop,
+                            )
+
+    def process_deletes(self, uowcommit, states):
+        # head object is being deleted, and we manage its list of
+        # child objects the child objects have to have their foreign
+        # key to the parent set to NULL this phase can be called
+        # safely for any cascade but is unnecessary if delete cascade
+        # is on.
+
+        if self.post_update or not self.passive_deletes == "all":
+            children_added = uowcommit.memo(("children_added", self), set)
+
+            for state in states:
+                history = uowcommit.get_attribute_history(
+                    state, self.key, self._passive_delete_flag
+                )
+                if history:
+                    for child in history.deleted:
+                        if (
+                            child is not None
+                            and self.hasparent(child) is False
+                        ):
+                            self._synchronize(
+                                state, child, None, True, uowcommit, False
+                            )
+                            if self.post_update and child:
+                                self._post_update(child, uowcommit, [state])
+
+                    if self.post_update or not self.cascade.delete:
+                        for child in set(history.unchanged).difference(
+                            children_added
+                        ):
+                            if child is not None:
+                                self._synchronize(
+                                    state, child, None, True, uowcommit, False
+                                )
+                                if self.post_update and child:
+                                    self._post_update(
+                                        child, uowcommit, [state]
+                                    )
+
+                    # technically, we can even remove each child from the
+                    # collection here too.  but this would be a somewhat
+                    # inconsistent behavior since it wouldn't happen
+                    # if the old parent wasn't deleted but child was moved.
+
+    def process_saves(self, uowcommit, states):
+        should_null_fks = (
+            not self.cascade.delete_orphan
+            and not self.passive_deletes == "all"
+        )
+
+        for state in states:
+            history = uowcommit.get_attribute_history(
+                state, self.key, attributes.PASSIVE_NO_INITIALIZE
+            )
+            if history:
+                for child in history.added:
+                    self._synchronize(
+                        state, child, None, False, uowcommit, False
+                    )
+                    if child is not None and self.post_update:
+                        self._post_update(child, uowcommit, [state])
+
+                for child in history.deleted:
+                    if (
+                        should_null_fks
+                        and not self.cascade.delete_orphan
+                        and not self.hasparent(child)
+                    ):
+                        self._synchronize(
+                            state, child, None, True, uowcommit, False
+                        )
+
+                if self._pks_changed(uowcommit, state):
+                    for child in history.unchanged:
+                        self._synchronize(
+                            state, child, None, False, uowcommit, True
+                        )
+
+    def _synchronize(
+        self, state, child, associationrow, clearkeys, uowcommit, pks_changed
+    ):
+        source = state
+        dest = child
+        self._verify_canload(child)
+        if dest is None or (
+            not self.post_update and uowcommit.is_deleted(dest)
+        ):
+            return
+        if clearkeys:
+            sync.clear(dest, self.mapper, self.prop.synchronize_pairs)
+        else:
+            sync.populate(
+                source,
+                self.parent,
+                dest,
+                self.mapper,
+                self.prop.synchronize_pairs,
+                uowcommit,
+                self.passive_updates and pks_changed,
+            )
+
+    def _pks_changed(self, uowcommit, state):
+        return sync.source_modified(
+            uowcommit, state, self.parent, self.prop.synchronize_pairs
+        )
+
+
+class ManyToOneDP(DependencyProcessor):
+    def __init__(self, prop):
+        DependencyProcessor.__init__(self, prop)
+        for mapper in self.mapper.self_and_descendants:
+            mapper._dependency_processors.append(DetectKeySwitch(prop))
+
+    def per_property_dependencies(
+        self,
+        uow,
+        parent_saves,
+        child_saves,
+        parent_deletes,
+        child_deletes,
+        after_save,
+        before_delete,
+    ):
+
+        if self.post_update:
+            parent_post_updates = unitofwork.PostUpdateAll(
+                uow, self.parent.primary_base_mapper, False
+            )
+            parent_pre_updates = unitofwork.PostUpdateAll(
+                uow, self.parent.primary_base_mapper, True
+            )
+
+            uow.dependencies.update(
+                [
+                    (child_saves, after_save),
+                    (parent_saves, after_save),
+                    (after_save, parent_post_updates),
+                    (after_save, parent_pre_updates),
+                    (before_delete, parent_pre_updates),
+                    (parent_pre_updates, child_deletes),
+                    (parent_pre_updates, parent_deletes),
+                ]
+            )
+        else:
+            uow.dependencies.update(
+                [
+                    (child_saves, after_save),
+                    (after_save, parent_saves),
+                    (parent_saves, child_deletes),
+                    (parent_deletes, child_deletes),
+                ]
+            )
+
+    def per_state_dependencies(
+        self,
+        uow,
+        save_parent,
+        delete_parent,
+        child_action,
+        after_save,
+        before_delete,
+        isdelete,
+        childisdelete,
+    ):
+
+        if self.post_update:
+
+            if not isdelete:
+                parent_post_updates = unitofwork.PostUpdateAll(
+                    uow, self.parent.primary_base_mapper, False
+                )
+                if childisdelete:
+                    uow.dependencies.update(
+                        [
+                            (after_save, parent_post_updates),
+                            (parent_post_updates, child_action),
+                        ]
+                    )
+                else:
+                    uow.dependencies.update(
+                        [
+                            (save_parent, after_save),
+                            (child_action, after_save),
+                            (after_save, parent_post_updates),
+                        ]
+                    )
+            else:
+                parent_pre_updates = unitofwork.PostUpdateAll(
+                    uow, self.parent.primary_base_mapper, True
+                )
+
+                uow.dependencies.update(
+                    [
+                        (before_delete, parent_pre_updates),
+                        (parent_pre_updates, delete_parent),
+                        (parent_pre_updates, child_action),
+                    ]
+                )
+
+        elif not isdelete:
+            if not childisdelete:
+                uow.dependencies.update(
+                    [(child_action, after_save), (after_save, save_parent)]
+                )
+            else:
+                uow.dependencies.update([(after_save, save_parent)])
+
+        else:
+            if childisdelete:
+                uow.dependencies.update([(delete_parent, child_action)])
+
+    def presort_deletes(self, uowcommit, states):
+        if self.cascade.delete or self.cascade.delete_orphan:
+            for state in states:
+                history = uowcommit.get_attribute_history(
+                    state, self.key, self._passive_delete_flag
+                )
+                if history:
+                    if self.cascade.delete_orphan:
+                        todelete = history.sum()
+                    else:
+                        todelete = history.non_deleted()
+                    for child in todelete:
+                        if child is None:
+                            continue
+                        uowcommit.register_object(
+                            child,
+                            isdelete=True,
+                            operation="delete",
+                            prop=self.prop,
+                        )
+                        t = self.mapper.cascade_iterator("delete", child)
+                        for c, m, st_, dct_ in t:
+                            uowcommit.register_object(st_, isdelete=True)
+
+    def presort_saves(self, uowcommit, states):
+        for state in states:
+            uowcommit.register_object(state, operation="add", prop=self.prop)
+            if self.cascade.delete_orphan:
+                history = uowcommit.get_attribute_history(
+                    state, self.key, self._passive_delete_flag
+                )
+                if history:
+                    for child in history.deleted:
+                        if self.hasparent(child) is False:
+                            uowcommit.register_object(
+                                child,
+                                isdelete=True,
+                                operation="delete",
+                                prop=self.prop,
+                            )
+
+                            t = self.mapper.cascade_iterator("delete", child)
+                            for c, m, st_, dct_ in t:
+                                uowcommit.register_object(st_, isdelete=True)
+
+    def process_deletes(self, uowcommit, states):
+        if (
+            self.post_update
+            and not self.cascade.delete_orphan
+            and not self.passive_deletes == "all"
+        ):
+
+            # post_update means we have to update our
+            # row to not reference the child object
+            # before we can DELETE the row
+            for state in states:
+                self._synchronize(state, None, None, True, uowcommit)
+                if state and self.post_update:
+                    history = uowcommit.get_attribute_history(
+                        state, self.key, self._passive_delete_flag
+                    )
+                    if history:
+                        self._post_update(
+                            state, uowcommit, history.sum(), is_m2o_delete=True
+                        )
+
+    def process_saves(self, uowcommit, states):
+        for state in states:
+            history = uowcommit.get_attribute_history(
+                state, self.key, attributes.PASSIVE_NO_INITIALIZE
+            )
+            if history:
+                if history.added:
+                    for child in history.added:
+                        self._synchronize(
+                            state, child, None, False, uowcommit, "add"
+                        )
+                elif history.deleted:
+                    self._synchronize(
+                        state, None, None, True, uowcommit, "delete"
+                    )
+                if self.post_update:
+                    self._post_update(state, uowcommit, history.sum())
+
+    def _synchronize(
+        self,
+        state,
+        child,
+        associationrow,
+        clearkeys,
+        uowcommit,
+        operation=None,
+    ):
+        if state is None or (
+            not self.post_update and uowcommit.is_deleted(state)
+        ):
+            return
+
+        if (
+            operation is not None
+            and child is not None
+            and not uowcommit.session._contains_state(child)
+        ):
+            util.warn(
+                "Object of type %s not in session, %s "
+                "operation along '%s' won't proceed"
+                % (mapperutil.state_class_str(child), operation, self.prop)
+            )
+            return
+
+        if clearkeys or child is None:
+            sync.clear(state, self.parent, self.prop.synchronize_pairs)
+        else:
+            self._verify_canload(child)
+            sync.populate(
+                child,
+                self.mapper,
+                state,
+                self.parent,
+                self.prop.synchronize_pairs,
+                uowcommit,
+                False,
+            )
+
+
+class DetectKeySwitch(DependencyProcessor):
+    """For many-to-one relationships with no one-to-many backref,
+    searches for parents through the unit of work when a primary
+    key has changed and updates them.
+
+    Theoretically, this approach could be expanded to support transparent
+    deletion of objects referenced via many-to-one as well, although
+    the current attribute system doesn't do enough bookkeeping for this
+    to be efficient.
+
+    """
+
+    def per_property_preprocessors(self, uow):
+        if self.prop._reverse_property:
+            if self.passive_updates:
+                return
+            else:
+                if False in (
+                    prop.passive_updates
+                    for prop in self.prop._reverse_property
+                ):
+                    return
+
+        uow.register_preprocessor(self, False)
+
+    def per_property_flush_actions(self, uow):
+        parent_saves = unitofwork.SaveUpdateAll(uow, self.parent.base_mapper)
+        after_save = unitofwork.ProcessAll(uow, self, False, False)
+        uow.dependencies.update([(parent_saves, after_save)])
+
+    def per_state_flush_actions(self, uow, states, isdelete):
+        pass
+
+    def presort_deletes(self, uowcommit, states):
+        pass
+
+    def presort_saves(self, uow, states):
+        if not self.passive_updates:
+            # for non-passive updates, register in the preprocess stage
+            # so that mapper save_obj() gets a hold of changes
+            self._process_key_switches(states, uow)
+
+    def prop_has_changes(self, uow, states, isdelete):
+        if not isdelete and self.passive_updates:
+            d = self._key_switchers(uow, states)
+            return bool(d)
+
+        return False
+
+    def process_deletes(self, uowcommit, states):
+        assert False
+
+    def process_saves(self, uowcommit, states):
+        # for passive updates, register objects in the process stage
+        # so that we avoid ManyToOneDP's registering the object without
+        # the listonly flag in its own preprocess stage (results in UPDATE)
+        # statements being emitted
+        assert self.passive_updates
+        self._process_key_switches(states, uowcommit)
+
+    def _key_switchers(self, uow, states):
+        switched, notswitched = uow.memo(
+            ("pk_switchers", self), lambda: (set(), set())
+        )
+
+        allstates = switched.union(notswitched)
+        for s in states:
+            if s not in allstates:
+                if self._pks_changed(uow, s):
+                    switched.add(s)
+                else:
+                    notswitched.add(s)
+        return switched
+
+    def _process_key_switches(self, deplist, uowcommit):
+        switchers = self._key_switchers(uowcommit, deplist)
+        if switchers:
+            # if primary key values have actually changed somewhere, perform
+            # a linear search through the UOW in search of a parent.
+            for state in uowcommit.session.identity_map.all_states():
+                if not issubclass(state.class_, self.parent.class_):
+                    continue
+                dict_ = state.dict
+                related = state.get_impl(self.key).get(
+                    state, dict_, passive=self._passive_update_flag
+                )
+                if (
+                    related is not attributes.PASSIVE_NO_RESULT
+                    and related is not None
+                ):
+                    if self.prop.uselist:
+                        if not related:
+                            continue
+                        related_obj = related[0]
+                    else:
+                        related_obj = related
+                    related_state = attributes.instance_state(related_obj)
+                    if related_state in switchers:
+                        uowcommit.register_object(
+                            state, False, self.passive_updates
+                        )
+                        sync.populate(
+                            related_state,
+                            self.mapper,
+                            state,
+                            self.parent,
+                            self.prop.synchronize_pairs,
+                            uowcommit,
+                            self.passive_updates,
+                        )
+
+    def _pks_changed(self, uowcommit, state):
+        return bool(state.key) and sync.source_modified(
+            uowcommit, state, self.mapper, self.prop.synchronize_pairs
+        )
+
+
+class ManyToManyDP(DependencyProcessor):
+    def per_property_dependencies(
+        self,
+        uow,
+        parent_saves,
+        child_saves,
+        parent_deletes,
+        child_deletes,
+        after_save,
+        before_delete,
+    ):
+
+        uow.dependencies.update(
+            [
+                (parent_saves, after_save),
+                (child_saves, after_save),
+                (after_save, child_deletes),
+                # a rowswitch on the parent from  deleted to saved
+                # can make this one occur, as the "save" may remove
+                # an element from the
+                # "deleted" list before we have a chance to
+                # process its child rows
+                (before_delete, parent_saves),
+                (before_delete, parent_deletes),
+                (before_delete, child_deletes),
+                (before_delete, child_saves),
+            ]
+        )
+
+    def per_state_dependencies(
+        self,
+        uow,
+        save_parent,
+        delete_parent,
+        child_action,
+        after_save,
+        before_delete,
+        isdelete,
+        childisdelete,
+    ):
+        if not isdelete:
+            if childisdelete:
+                uow.dependencies.update(
+                    [(save_parent, after_save), (after_save, child_action)]
+                )
+            else:
+                uow.dependencies.update(
+                    [(save_parent, after_save), (child_action, after_save)]
+                )
+        else:
+            uow.dependencies.update(
+                [(before_delete, child_action), (before_delete, delete_parent)]
+            )
+
+    def presort_deletes(self, uowcommit, states):
+        # TODO: no tests fail if this whole
+        # thing is removed !!!!
+        if not self.passive_deletes:
+            # if no passive deletes, load history on
+            # the collection, so that prop_has_changes()
+            # returns True
+            for state in states:
+                uowcommit.get_attribute_history(
+                    state, self.key, self._passive_delete_flag
+                )
+
+    def presort_saves(self, uowcommit, states):
+        if not self.passive_updates:
+            # if no passive updates, load history on
+            # each collection where parent has changed PK,
+            # so that prop_has_changes() returns True
+            for state in states:
+                if self._pks_changed(uowcommit, state):
+                    history = uowcommit.get_attribute_history(
+                        state, self.key, attributes.PASSIVE_OFF
+                    )
+
+        if not self.cascade.delete_orphan:
+            return
+
+        # check for child items removed from the collection
+        # if delete_orphan check is turned on.
+        for state in states:
+            history = uowcommit.get_attribute_history(
+                state, self.key, attributes.PASSIVE_NO_INITIALIZE
+            )
+            if history:
+                for child in history.deleted:
+                    if self.hasparent(child) is False:
+                        uowcommit.register_object(
+                            child,
+                            isdelete=True,
+                            operation="delete",
+                            prop=self.prop,
+                        )
+                        for c, m, st_, dct_ in self.mapper.cascade_iterator(
+                            "delete", child
+                        ):
+                            uowcommit.register_object(st_, isdelete=True)
+
+    def process_deletes(self, uowcommit, states):
+        secondary_delete = []
+        secondary_insert = []
+        secondary_update = []
+
+        processed = self._get_reversed_processed_set(uowcommit)
+        tmp = set()
+        for state in states:
+            # this history should be cached already, as
+            # we loaded it in preprocess_deletes
+            history = uowcommit.get_attribute_history(
+                state, self.key, self._passive_delete_flag
+            )
+            if history:
+                for child in history.non_added():
+                    if child is None or (
+                        processed is not None and (state, child) in processed
+                    ):
+                        continue
+                    associationrow = {}
+                    if not self._synchronize(
+                        state,
+                        child,
+                        associationrow,
+                        False,
+                        uowcommit,
+                        "delete",
+                    ):
+                        continue
+                    secondary_delete.append(associationrow)
+
+                tmp.update((c, state) for c in history.non_added())
+
+        if processed is not None:
+            processed.update(tmp)
+
+        self._run_crud(
+            uowcommit, secondary_insert, secondary_update, secondary_delete
+        )
+
+    def process_saves(self, uowcommit, states):
+        secondary_delete = []
+        secondary_insert = []
+        secondary_update = []
+
+        processed = self._get_reversed_processed_set(uowcommit)
+        tmp = set()
+
+        for state in states:
+            need_cascade_pks = not self.passive_updates and self._pks_changed(
+                uowcommit, state
+            )
+            if need_cascade_pks:
+                passive = attributes.PASSIVE_OFF
+            else:
+                passive = attributes.PASSIVE_NO_INITIALIZE
+            history = uowcommit.get_attribute_history(state, self.key, passive)
+            if history:
+                for child in history.added:
+                    if processed is not None and (state, child) in processed:
+                        continue
+                    associationrow = {}
+                    if not self._synchronize(
+                        state, child, associationrow, False, uowcommit, "add"
+                    ):
+                        continue
+                    secondary_insert.append(associationrow)
+                for child in history.deleted:
+                    if processed is not None and (state, child) in processed:
+                        continue
+                    associationrow = {}
+                    if not self._synchronize(
+                        state,
+                        child,
+                        associationrow,
+                        False,
+                        uowcommit,
+                        "delete",
+                    ):
+                        continue
+                    secondary_delete.append(associationrow)
+
+                tmp.update((c, state) for c in history.added + history.deleted)
+
+                if need_cascade_pks:
+
+                    for child in history.unchanged:
+                        associationrow = {}
+                        sync.update(
+                            state,
+                            self.parent,
+                            associationrow,
+                            "old_",
+                            self.prop.synchronize_pairs,
+                        )
+                        sync.update(
+                            child,
+                            self.mapper,
+                            associationrow,
+                            "old_",
+                            self.prop.secondary_synchronize_pairs,
+                        )
+
+                        secondary_update.append(associationrow)
+
+        if processed is not None:
+            processed.update(tmp)
+
+        self._run_crud(
+            uowcommit, secondary_insert, secondary_update, secondary_delete
+        )
+
+    def _run_crud(
+        self, uowcommit, secondary_insert, secondary_update, secondary_delete
+    ):
+        connection = uowcommit.transaction.connection(self.mapper)
+
+        if secondary_delete:
+            associationrow = secondary_delete[0]
+            statement = self.secondary.delete().where(
+                sql.and_(
+                    *[
+                        c == sql.bindparam(c.key, type_=c.type)
+                        for c in self.secondary.c
+                        if c.key in associationrow
+                    ]
+                )
+            )
+            result = connection.execute(statement, secondary_delete)
+
+            if (
+                result.supports_sane_multi_rowcount()
+            ) and result.rowcount != len(secondary_delete):
+                raise exc.StaleDataError(
+                    "DELETE statement on table '%s' expected to delete "
+                    "%d row(s); Only %d were matched."
+                    % (
+                        self.secondary.description,
+                        len(secondary_delete),
+                        result.rowcount,
+                    )
+                )
+
+        if secondary_update:
+            associationrow = secondary_update[0]
+            statement = self.secondary.update().where(
+                sql.and_(
+                    *[
+                        c == sql.bindparam("old_" + c.key, type_=c.type)
+                        for c in self.secondary.c
+                        if c.key in associationrow
+                    ]
+                )
+            )
+            result = connection.execute(statement, secondary_update)
+
+            if (
+                result.supports_sane_multi_rowcount()
+            ) and result.rowcount != len(secondary_update):
+                raise exc.StaleDataError(
+                    "UPDATE statement on table '%s' expected to update "
+                    "%d row(s); Only %d were matched."
+                    % (
+                        self.secondary.description,
+                        len(secondary_update),
+                        result.rowcount,
+                    )
+                )
+
+        if secondary_insert:
+            statement = self.secondary.insert()
+            connection.execute(statement, secondary_insert)
+
+    def _synchronize(
+        self, state, child, associationrow, clearkeys, uowcommit, operation
+    ):
+
+        # this checks for None if uselist=True
+        self._verify_canload(child)
+
+        # but if uselist=False we get here.   If child is None,
+        # no association row can be generated, so return.
+        if child is None:
+            return False
+
+        if child is not None and not uowcommit.session._contains_state(child):
+            if not child.deleted:
+                util.warn(
+                    "Object of type %s not in session, %s "
+                    "operation along '%s' won't proceed"
+                    % (mapperutil.state_class_str(child), operation, self.prop)
+                )
+            return False
+
+        sync.populate_dict(
+            state, self.parent, associationrow, self.prop.synchronize_pairs
+        )
+        sync.populate_dict(
+            child,
+            self.mapper,
+            associationrow,
+            self.prop.secondary_synchronize_pairs,
+        )
+
+        return True
+
+    def _pks_changed(self, uowcommit, state):
+        return sync.source_modified(
+            uowcommit, state, self.parent, self.prop.synchronize_pairs
+        )
+
+
+_direction_to_processor = {
+    ONETOMANY: OneToManyDP,
+    MANYTOONE: ManyToOneDP,
+    MANYTOMANY: ManyToManyDP,
+}