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Diffstat (limited to 'lib/sqlalchemy/orm/unitofwork.py')
| -rw-r--r-- | lib/sqlalchemy/orm/unitofwork.py | 784 |
1 files changed, 784 insertions, 0 deletions
diff --git a/lib/sqlalchemy/orm/unitofwork.py b/lib/sqlalchemy/orm/unitofwork.py new file mode 100644 index 0000000..2257637 --- /dev/null +++ b/lib/sqlalchemy/orm/unitofwork.py @@ -0,0 +1,784 @@ +# orm/unitofwork.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 + +"""The internals for the unit of work system. + +The session's flush() process passes objects to a contextual object +here, which assembles flush tasks based on mappers and their properties, +organizes them in order of dependency, and executes. + +""" + +from . import attributes +from . import exc as orm_exc +from . import util as orm_util +from .. import event +from .. import util +from ..util import topological + + +def _warn_for_cascade_backrefs(state, prop): + util.warn_deprecated_20( + '"%s" object is being merged into a Session along the backref ' + 'cascade path for relationship "%s"; in SQLAlchemy 2.0, this ' + "reverse cascade will not take place. Set cascade_backrefs to " + "False in either the relationship() or backref() function for " + "the 2.0 behavior; or to set globally for the whole " + "Session, set the future=True flag" % (state.class_.__name__, prop), + code="s9r1", + ) + + +def track_cascade_events(descriptor, prop): + """Establish event listeners on object attributes which handle + cascade-on-set/append. + + """ + key = prop.key + + def append(state, item, initiator): + # process "save_update" cascade rules for when + # an instance is appended to the list of another instance + + if item is None: + return + + sess = state.session + if sess: + if sess._warn_on_events: + sess._flush_warning("collection append") + + prop = state.manager.mapper._props[key] + item_state = attributes.instance_state(item) + + if ( + prop._cascade.save_update + and ( + (prop.cascade_backrefs and not sess.future) + or key == initiator.key + ) + and not sess._contains_state(item_state) + ): + if key != initiator.key: + _warn_for_cascade_backrefs(item_state, prop) + sess._save_or_update_state(item_state) + return item + + def remove(state, item, initiator): + if item is None: + return + + sess = state.session + + prop = state.manager.mapper._props[key] + + if sess and sess._warn_on_events: + sess._flush_warning( + "collection remove" + if prop.uselist + else "related attribute delete" + ) + + if ( + item is not None + and item is not attributes.NEVER_SET + and item is not attributes.PASSIVE_NO_RESULT + and prop._cascade.delete_orphan + ): + # expunge pending orphans + item_state = attributes.instance_state(item) + + if prop.mapper._is_orphan(item_state): + if sess and item_state in sess._new: + sess.expunge(item) + else: + # the related item may or may not itself be in a + # Session, however the parent for which we are catching + # the event is not in a session, so memoize this on the + # item + item_state._orphaned_outside_of_session = True + + def set_(state, newvalue, oldvalue, initiator): + # process "save_update" cascade rules for when an instance + # is attached to another instance + if oldvalue is newvalue: + return newvalue + + sess = state.session + if sess: + + if sess._warn_on_events: + sess._flush_warning("related attribute set") + + prop = state.manager.mapper._props[key] + if newvalue is not None: + newvalue_state = attributes.instance_state(newvalue) + if ( + prop._cascade.save_update + and ( + (prop.cascade_backrefs and not sess.future) + or key == initiator.key + ) + and not sess._contains_state(newvalue_state) + ): + if key != initiator.key: + _warn_for_cascade_backrefs(newvalue_state, prop) + sess._save_or_update_state(newvalue_state) + + if ( + oldvalue is not None + and oldvalue is not attributes.NEVER_SET + and oldvalue is not attributes.PASSIVE_NO_RESULT + and prop._cascade.delete_orphan + ): + # possible to reach here with attributes.NEVER_SET ? + oldvalue_state = attributes.instance_state(oldvalue) + + if oldvalue_state in sess._new and prop.mapper._is_orphan( + oldvalue_state + ): + sess.expunge(oldvalue) + return newvalue + + event.listen(descriptor, "append_wo_mutation", append, raw=True) + event.listen(descriptor, "append", append, raw=True, retval=True) + event.listen(descriptor, "remove", remove, raw=True, retval=True) + event.listen(descriptor, "set", set_, raw=True, retval=True) + + +class UOWTransaction(object): + def __init__(self, session): + self.session = session + + # dictionary used by external actors to + # store arbitrary state information. + self.attributes = {} + + # dictionary of mappers to sets of + # DependencyProcessors, which are also + # set to be part of the sorted flush actions, + # which have that mapper as a parent. + self.deps = util.defaultdict(set) + + # dictionary of mappers to sets of InstanceState + # items pending for flush which have that mapper + # as a parent. + self.mappers = util.defaultdict(set) + + # a dictionary of Preprocess objects, which gather + # additional states impacted by the flush + # and determine if a flush action is needed + self.presort_actions = {} + + # dictionary of PostSortRec objects, each + # one issues work during the flush within + # a certain ordering. + self.postsort_actions = {} + + # a set of 2-tuples, each containing two + # PostSortRec objects where the second + # is dependent on the first being executed + # first + self.dependencies = set() + + # dictionary of InstanceState-> (isdelete, listonly) + # tuples, indicating if this state is to be deleted + # or insert/updated, or just refreshed + self.states = {} + + # tracks InstanceStates which will be receiving + # a "post update" call. Keys are mappers, + # values are a set of states and a set of the + # columns which should be included in the update. + self.post_update_states = util.defaultdict(lambda: (set(), set())) + + @property + def has_work(self): + return bool(self.states) + + def was_already_deleted(self, state): + """Return ``True`` if the given state is expired and was deleted + previously. + """ + if state.expired: + try: + state._load_expired(state, attributes.PASSIVE_OFF) + except orm_exc.ObjectDeletedError: + self.session._remove_newly_deleted([state]) + return True + return False + + def is_deleted(self, state): + """Return ``True`` if the given state is marked as deleted + within this uowtransaction.""" + + return state in self.states and self.states[state][0] + + def memo(self, key, callable_): + if key in self.attributes: + return self.attributes[key] + else: + self.attributes[key] = ret = callable_() + return ret + + def remove_state_actions(self, state): + """Remove pending actions for a state from the uowtransaction.""" + + isdelete = self.states[state][0] + + self.states[state] = (isdelete, True) + + def get_attribute_history( + self, state, key, passive=attributes.PASSIVE_NO_INITIALIZE + ): + """Facade to attributes.get_state_history(), including + caching of results.""" + + hashkey = ("history", state, key) + + # cache the objects, not the states; the strong reference here + # prevents newly loaded objects from being dereferenced during the + # flush process + + if hashkey in self.attributes: + history, state_history, cached_passive = self.attributes[hashkey] + # if the cached lookup was "passive" and now + # we want non-passive, do a non-passive lookup and re-cache + + if ( + not cached_passive & attributes.SQL_OK + and passive & attributes.SQL_OK + ): + impl = state.manager[key].impl + history = impl.get_history( + state, + state.dict, + attributes.PASSIVE_OFF + | attributes.LOAD_AGAINST_COMMITTED + | attributes.NO_RAISE, + ) + if history and impl.uses_objects: + state_history = history.as_state() + else: + state_history = history + self.attributes[hashkey] = (history, state_history, passive) + else: + impl = state.manager[key].impl + # TODO: store the history as (state, object) tuples + # so we don't have to keep converting here + history = impl.get_history( + state, + state.dict, + passive + | attributes.LOAD_AGAINST_COMMITTED + | attributes.NO_RAISE, + ) + if history and impl.uses_objects: + state_history = history.as_state() + else: + state_history = history + self.attributes[hashkey] = (history, state_history, passive) + + return state_history + + def has_dep(self, processor): + return (processor, True) in self.presort_actions + + def register_preprocessor(self, processor, fromparent): + key = (processor, fromparent) + if key not in self.presort_actions: + self.presort_actions[key] = Preprocess(processor, fromparent) + + def register_object( + self, + state, + isdelete=False, + listonly=False, + cancel_delete=False, + operation=None, + prop=None, + ): + if not self.session._contains_state(state): + # this condition is normal when objects are registered + # as part of a relationship cascade operation. it should + # not occur for the top-level register from Session.flush(). + if not state.deleted and operation is not None: + util.warn( + "Object of type %s not in session, %s operation " + "along '%s' will not proceed" + % (orm_util.state_class_str(state), operation, prop) + ) + return False + + if state not in self.states: + mapper = state.manager.mapper + + if mapper not in self.mappers: + self._per_mapper_flush_actions(mapper) + + self.mappers[mapper].add(state) + self.states[state] = (isdelete, listonly) + else: + if not listonly and (isdelete or cancel_delete): + self.states[state] = (isdelete, False) + return True + + def register_post_update(self, state, post_update_cols): + mapper = state.manager.mapper.base_mapper + states, cols = self.post_update_states[mapper] + states.add(state) + cols.update(post_update_cols) + + def _per_mapper_flush_actions(self, mapper): + saves = SaveUpdateAll(self, mapper.base_mapper) + deletes = DeleteAll(self, mapper.base_mapper) + self.dependencies.add((saves, deletes)) + + for dep in mapper._dependency_processors: + dep.per_property_preprocessors(self) + + for prop in mapper.relationships: + if prop.viewonly: + continue + dep = prop._dependency_processor + dep.per_property_preprocessors(self) + + @util.memoized_property + def _mapper_for_dep(self): + """return a dynamic mapping of (Mapper, DependencyProcessor) to + True or False, indicating if the DependencyProcessor operates + on objects of that Mapper. + + The result is stored in the dictionary persistently once + calculated. + + """ + return util.PopulateDict( + lambda tup: tup[0]._props.get(tup[1].key) is tup[1].prop + ) + + def filter_states_for_dep(self, dep, states): + """Filter the given list of InstanceStates to those relevant to the + given DependencyProcessor. + + """ + mapper_for_dep = self._mapper_for_dep + return [s for s in states if mapper_for_dep[(s.manager.mapper, dep)]] + + def states_for_mapper_hierarchy(self, mapper, isdelete, listonly): + checktup = (isdelete, listonly) + for mapper in mapper.base_mapper.self_and_descendants: + for state in self.mappers[mapper]: + if self.states[state] == checktup: + yield state + + def _generate_actions(self): + """Generate the full, unsorted collection of PostSortRecs as + well as dependency pairs for this UOWTransaction. + + """ + # execute presort_actions, until all states + # have been processed. a presort_action might + # add new states to the uow. + while True: + ret = False + for action in list(self.presort_actions.values()): + if action.execute(self): + ret = True + if not ret: + break + + # see if the graph of mapper dependencies has cycles. + self.cycles = cycles = topological.find_cycles( + self.dependencies, list(self.postsort_actions.values()) + ) + + if cycles: + # if yes, break the per-mapper actions into + # per-state actions + convert = dict( + (rec, set(rec.per_state_flush_actions(self))) for rec in cycles + ) + + # rewrite the existing dependencies to point to + # the per-state actions for those per-mapper actions + # that were broken up. + for edge in list(self.dependencies): + if ( + None in edge + or edge[0].disabled + or edge[1].disabled + or cycles.issuperset(edge) + ): + self.dependencies.remove(edge) + elif edge[0] in cycles: + self.dependencies.remove(edge) + for dep in convert[edge[0]]: + self.dependencies.add((dep, edge[1])) + elif edge[1] in cycles: + self.dependencies.remove(edge) + for dep in convert[edge[1]]: + self.dependencies.add((edge[0], dep)) + + return set( + [a for a in self.postsort_actions.values() if not a.disabled] + ).difference(cycles) + + def execute(self): + postsort_actions = self._generate_actions() + + postsort_actions = sorted( + postsort_actions, + key=lambda item: item.sort_key, + ) + # sort = topological.sort(self.dependencies, postsort_actions) + # print "--------------" + # print "\ndependencies:", self.dependencies + # print "\ncycles:", self.cycles + # print "\nsort:", list(sort) + # print "\nCOUNT OF POSTSORT ACTIONS", len(postsort_actions) + + # execute + if self.cycles: + for subset in topological.sort_as_subsets( + self.dependencies, postsort_actions + ): + set_ = set(subset) + while set_: + n = set_.pop() + n.execute_aggregate(self, set_) + else: + for rec in topological.sort(self.dependencies, postsort_actions): + rec.execute(self) + + def finalize_flush_changes(self): + """Mark processed objects as clean / deleted after a successful + flush(). + + This method is called within the flush() method after the + execute() method has succeeded and the transaction has been committed. + + """ + if not self.states: + return + + states = set(self.states) + isdel = set( + s for (s, (isdelete, listonly)) in self.states.items() if isdelete + ) + other = states.difference(isdel) + if isdel: + self.session._remove_newly_deleted(isdel) + if other: + self.session._register_persistent(other) + + +class IterateMappersMixin(object): + def _mappers(self, uow): + if self.fromparent: + return iter( + m + for m in self.dependency_processor.parent.self_and_descendants + if uow._mapper_for_dep[(m, self.dependency_processor)] + ) + else: + return self.dependency_processor.mapper.self_and_descendants + + +class Preprocess(IterateMappersMixin): + __slots__ = ( + "dependency_processor", + "fromparent", + "processed", + "setup_flush_actions", + ) + + def __init__(self, dependency_processor, fromparent): + self.dependency_processor = dependency_processor + self.fromparent = fromparent + self.processed = set() + self.setup_flush_actions = False + + def execute(self, uow): + delete_states = set() + save_states = set() + + for mapper in self._mappers(uow): + for state in uow.mappers[mapper].difference(self.processed): + (isdelete, listonly) = uow.states[state] + if not listonly: + if isdelete: + delete_states.add(state) + else: + save_states.add(state) + + if delete_states: + self.dependency_processor.presort_deletes(uow, delete_states) + self.processed.update(delete_states) + if save_states: + self.dependency_processor.presort_saves(uow, save_states) + self.processed.update(save_states) + + if delete_states or save_states: + if not self.setup_flush_actions and ( + self.dependency_processor.prop_has_changes( + uow, delete_states, True + ) + or self.dependency_processor.prop_has_changes( + uow, save_states, False + ) + ): + self.dependency_processor.per_property_flush_actions(uow) + self.setup_flush_actions = True + return True + else: + return False + + +class PostSortRec(object): + __slots__ = ("disabled",) + + def __new__(cls, uow, *args): + key = (cls,) + args + if key in uow.postsort_actions: + return uow.postsort_actions[key] + else: + uow.postsort_actions[key] = ret = object.__new__(cls) + ret.disabled = False + return ret + + def execute_aggregate(self, uow, recs): + self.execute(uow) + + +class ProcessAll(IterateMappersMixin, PostSortRec): + __slots__ = "dependency_processor", "isdelete", "fromparent", "sort_key" + + def __init__(self, uow, dependency_processor, isdelete, fromparent): + self.dependency_processor = dependency_processor + self.sort_key = ( + "ProcessAll", + self.dependency_processor.sort_key, + isdelete, + ) + self.isdelete = isdelete + self.fromparent = fromparent + uow.deps[dependency_processor.parent.base_mapper].add( + dependency_processor + ) + + def execute(self, uow): + states = self._elements(uow) + if self.isdelete: + self.dependency_processor.process_deletes(uow, states) + else: + self.dependency_processor.process_saves(uow, states) + + def per_state_flush_actions(self, uow): + # this is handled by SaveUpdateAll and DeleteAll, + # since a ProcessAll should unconditionally be pulled + # into per-state if either the parent/child mappers + # are part of a cycle + return iter([]) + + def __repr__(self): + return "%s(%s, isdelete=%s)" % ( + self.__class__.__name__, + self.dependency_processor, + self.isdelete, + ) + + def _elements(self, uow): + for mapper in self._mappers(uow): + for state in uow.mappers[mapper]: + (isdelete, listonly) = uow.states[state] + if isdelete == self.isdelete and not listonly: + yield state + + +class PostUpdateAll(PostSortRec): + __slots__ = "mapper", "isdelete", "sort_key" + + def __init__(self, uow, mapper, isdelete): + self.mapper = mapper + self.isdelete = isdelete + self.sort_key = ("PostUpdateAll", mapper._sort_key, isdelete) + + @util.preload_module("sqlalchemy.orm.persistence") + def execute(self, uow): + persistence = util.preloaded.orm_persistence + states, cols = uow.post_update_states[self.mapper] + states = [s for s in states if uow.states[s][0] == self.isdelete] + + persistence.post_update(self.mapper, states, uow, cols) + + +class SaveUpdateAll(PostSortRec): + __slots__ = ("mapper", "sort_key") + + def __init__(self, uow, mapper): + self.mapper = mapper + self.sort_key = ("SaveUpdateAll", mapper._sort_key) + assert mapper is mapper.base_mapper + + @util.preload_module("sqlalchemy.orm.persistence") + def execute(self, uow): + util.preloaded.orm_persistence.save_obj( + self.mapper, + uow.states_for_mapper_hierarchy(self.mapper, False, False), + uow, + ) + + def per_state_flush_actions(self, uow): + states = list( + uow.states_for_mapper_hierarchy(self.mapper, False, False) + ) + base_mapper = self.mapper.base_mapper + delete_all = DeleteAll(uow, base_mapper) + for state in states: + # keep saves before deletes - + # this ensures 'row switch' operations work + action = SaveUpdateState(uow, state) + uow.dependencies.add((action, delete_all)) + yield action + + for dep in uow.deps[self.mapper]: + states_for_prop = uow.filter_states_for_dep(dep, states) + dep.per_state_flush_actions(uow, states_for_prop, False) + + def __repr__(self): + return "%s(%s)" % (self.__class__.__name__, self.mapper) + + +class DeleteAll(PostSortRec): + __slots__ = ("mapper", "sort_key") + + def __init__(self, uow, mapper): + self.mapper = mapper + self.sort_key = ("DeleteAll", mapper._sort_key) + assert mapper is mapper.base_mapper + + @util.preload_module("sqlalchemy.orm.persistence") + def execute(self, uow): + util.preloaded.orm_persistence.delete_obj( + self.mapper, + uow.states_for_mapper_hierarchy(self.mapper, True, False), + uow, + ) + + def per_state_flush_actions(self, uow): + states = list( + uow.states_for_mapper_hierarchy(self.mapper, True, False) + ) + base_mapper = self.mapper.base_mapper + save_all = SaveUpdateAll(uow, base_mapper) + for state in states: + # keep saves before deletes - + # this ensures 'row switch' operations work + action = DeleteState(uow, state) + uow.dependencies.add((save_all, action)) + yield action + + for dep in uow.deps[self.mapper]: + states_for_prop = uow.filter_states_for_dep(dep, states) + dep.per_state_flush_actions(uow, states_for_prop, True) + + def __repr__(self): + return "%s(%s)" % (self.__class__.__name__, self.mapper) + + +class ProcessState(PostSortRec): + __slots__ = "dependency_processor", "isdelete", "state", "sort_key" + + def __init__(self, uow, dependency_processor, isdelete, state): + self.dependency_processor = dependency_processor + self.sort_key = ("ProcessState", dependency_processor.sort_key) + self.isdelete = isdelete + self.state = state + + def execute_aggregate(self, uow, recs): + cls_ = self.__class__ + dependency_processor = self.dependency_processor + isdelete = self.isdelete + our_recs = [ + r + for r in recs + if r.__class__ is cls_ + and r.dependency_processor is dependency_processor + and r.isdelete is isdelete + ] + recs.difference_update(our_recs) + states = [self.state] + [r.state for r in our_recs] + if isdelete: + dependency_processor.process_deletes(uow, states) + else: + dependency_processor.process_saves(uow, states) + + def __repr__(self): + return "%s(%s, %s, delete=%s)" % ( + self.__class__.__name__, + self.dependency_processor, + orm_util.state_str(self.state), + self.isdelete, + ) + + +class SaveUpdateState(PostSortRec): + __slots__ = "state", "mapper", "sort_key" + + def __init__(self, uow, state): + self.state = state + self.mapper = state.mapper.base_mapper + self.sort_key = ("ProcessState", self.mapper._sort_key) + + @util.preload_module("sqlalchemy.orm.persistence") + def execute_aggregate(self, uow, recs): + persistence = util.preloaded.orm_persistence + cls_ = self.__class__ + mapper = self.mapper + our_recs = [ + r for r in recs if r.__class__ is cls_ and r.mapper is mapper + ] + recs.difference_update(our_recs) + persistence.save_obj( + mapper, [self.state] + [r.state for r in our_recs], uow + ) + + def __repr__(self): + return "%s(%s)" % ( + self.__class__.__name__, + orm_util.state_str(self.state), + ) + + +class DeleteState(PostSortRec): + __slots__ = "state", "mapper", "sort_key" + + def __init__(self, uow, state): + self.state = state + self.mapper = state.mapper.base_mapper + self.sort_key = ("DeleteState", self.mapper._sort_key) + + @util.preload_module("sqlalchemy.orm.persistence") + def execute_aggregate(self, uow, recs): + persistence = util.preloaded.orm_persistence + cls_ = self.__class__ + mapper = self.mapper + our_recs = [ + r for r in recs if r.__class__ is cls_ and r.mapper is mapper + ] + recs.difference_update(our_recs) + states = [self.state] + [r.state for r in our_recs] + persistence.delete_obj( + mapper, [s for s in states if uow.states[s][0]], uow + ) + + def __repr__(self): + return "%s(%s)" % ( + self.__class__.__name__, + orm_util.state_str(self.state), + ) |