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strategies.py @ 3

リビジョン 3, 36.3 KB (コミッタ: kohda, 14 年前)
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1	# strategies.py
2	# Copyright (C) 2005, 2006, 2007, 2008, 2009 Michael Bayer mike_mp@zzzcomputing.com
3	#
4	# This module is part of SQLAlchemy and is released under
5	# the MIT License: http://www.opensource.org/licenses/mit-license.php
6
7	"""sqlalchemy.orm.interfaces.LoaderStrategy implementations, and related MapperOptions."""
8
9	import sqlalchemy.exceptions as sa_exc
10	from sqlalchemy import sql, util, log
11	from sqlalchemy.sql import util as sql_util
12	from sqlalchemy.sql import visitors, expression, operators
13	from sqlalchemy.orm import mapper, attributes, interfaces
14	from sqlalchemy.orm.interfaces import (
15	LoaderStrategy, StrategizedOption, MapperOption, PropertyOption,
16	serialize_path, deserialize_path, StrategizedProperty
17	)
18	from sqlalchemy.orm import session as sessionlib
19	from sqlalchemy.orm import util as mapperutil
20
21	def _register_attribute(strategy, mapper, useobject,
22	compare_function=None,
23	typecallable=None,
24	copy_function=None,
25	mutable_scalars=False,
26	uselist=False,
27	callable_=None,
28	proxy_property=None,
29	active_history=False,
30	impl_class=None,
31	**kw
32	):
33
34	prop = strategy.parent_property
35	attribute_ext = list(util.to_list(prop.extension, default=[]))
36
37	if useobject and prop.single_parent:
38	attribute_ext.append(_SingleParentValidator(prop))
39
40	if getattr(prop, 'backref', None):
41	attribute_ext.append(prop.backref.extension)
42
43	if prop.key in prop.parent._validators:
44	attribute_ext.append(mapperutil.Validator(prop.key, prop.parent._validators[prop.key]))
45
46	if useobject:
47	attribute_ext.append(sessionlib.UOWEventHandler(prop.key))
48
49	for m in mapper.polymorphic_iterator():
50	if prop is m._props.get(prop.key):
51
52	attributes.register_attribute_impl(
53	m.class_,
54	prop.key,
55	parent_token=prop,
56	mutable_scalars=mutable_scalars,
57	uselist=uselist,
58	copy_function=copy_function,
59	compare_function=compare_function,
60	useobject=useobject,
61	extension=attribute_ext,
62	trackparent=useobject,
63	typecallable=typecallable,
64	callable_=callable_,
65	active_history=active_history,
66	impl_class=impl_class,
67	**kw
68	)
69
70	class UninstrumentedColumnLoader(LoaderStrategy):
71	"""Represent the strategy for a MapperProperty that doesn't instrument the class.
72
73	The polymorphic_on argument of mapper() often results in this,
74	if the argument is against the with_polymorphic selectable.
75
76	"""
77	def init(self):
78	self.columns = self.parent_property.columns
79
80	def setup_query(self, context, entity, path, adapter, column_collection=None, **kwargs):
81	for c in self.columns:
82	if adapter:
83	c = adapter.columns[c]
84	column_collection.append(c)
85
86	def create_row_processor(self, selectcontext, path, mapper, row, adapter):
87	return (None, None)
88
89	class ColumnLoader(LoaderStrategy):
90	"""Strategize the loading of a plain column-based MapperProperty."""
91
92	def init(self):
93	self.columns = self.parent_property.columns
94	self.is_composite = hasattr(self.parent_property, 'composite_class')
95
96	def setup_query(self, context, entity, path, adapter, column_collection=None, **kwargs):
97	for c in self.columns:
98	if adapter:
99	c = adapter.columns[c]
100	column_collection.append(c)
101
102	def init_class_attribute(self, mapper):
103	self.is_class_level = True
104	coltype = self.columns[0].type
105	active_history = self.columns[0].primary_key # TODO: check all columns ? check for foreign Key as well?
106
107	_register_attribute(self, mapper, useobject=False,
108	compare_function=coltype.compare_values,
109	copy_function=coltype.copy_value,
110	mutable_scalars=self.columns[0].type.is_mutable(),
111	active_history = active_history
112	)
113
114	def create_row_processor(self, selectcontext, path, mapper, row, adapter):
115	key, col = self.key, self.columns[0]
116	if adapter:
117	col = adapter.columns[col]
118	if col is not None and col in row:
119	def new_execute(state, dict_, row, **flags):
120	dict_[key] = row[col]
121
122	if self._should_log_debug:
123	new_execute = self.debug_callable(new_execute, self.logger,
124	"%s returning active column fetcher" % self,
125	lambda state, dict_, row, **flags: "%s populating %s" % \
126	(self,
127	mapperutil.state_attribute_str(state, key))
128	)
129	return (new_execute, None)
130	else:
131	def new_execute(state, dict_, row, isnew, **flags):
132	if isnew:
133	state.expire_attributes([key])
134	if self._should_log_debug:
135	self.logger.debug("%s deferring load" % self)
136	return (new_execute, None)
137
138	log.class_logger(ColumnLoader)
139
140	class CompositeColumnLoader(ColumnLoader):
141	"""Strategize the loading of a composite column-based MapperProperty."""
142
143	def init_class_attribute(self, mapper):
144	self.is_class_level = True
145	self.logger.info("%s register managed composite attribute" % self)
146
147	def copy(obj):
148	if obj is None:
149	return None
150	return self.parent_property.composite_class(*obj.__composite_values__())
151
152	def compare(a, b):
153	if a is None or b is None:
154	return a is b
155
156	for col, aprop, bprop in zip(self.columns,
157	a.__composite_values__(),
158	b.__composite_values__()):
159	if not col.type.compare_values(aprop, bprop):
160	return False
161	else:
162	return True
163
164	_register_attribute(self, mapper, useobject=False,
165	compare_function=compare,
166	copy_function=copy,
167	mutable_scalars=True
168	#active_history ?
169	)
170
171	def create_row_processor(self, selectcontext, path, mapper, row, adapter):
172	key, columns, composite_class = self.key, self.columns, self.parent_property.composite_class
173	if adapter:
174	columns = [adapter.columns[c] for c in columns]
175	for c in columns:
176	if c not in row:
177	def new_execute(state, dict_, row, isnew, **flags):
178	if isnew:
179	state.expire_attributes([key])
180	if self._should_log_debug:
181	self.logger.debug("%s deferring load" % self)
182	return (new_execute, None)
183	else:
184	def new_execute(state, dict_, row, **flags):
185	dict_[key] = composite_class(*[row[c] for c in columns])
186
187	if self._should_log_debug:
188	new_execute = self.debug_callable(new_execute, self.logger,
189	"%s returning active composite column fetcher" % self,
190	lambda state, dict_, row, **flags: "populating %s" % \
191	(mapperutil.state_attribute_str(state, key))
192	)
193
194	return (new_execute, None)
195
196	log.class_logger(CompositeColumnLoader)
197
198	class DeferredColumnLoader(LoaderStrategy):
199	"""Strategize the loading of a deferred column-based MapperProperty."""
200
201	def create_row_processor(self, selectcontext, path, mapper, row, adapter):
202	col = self.columns[0]
203	if adapter:
204	col = adapter.columns[col]
205	if col in row:
206	return self.parent_property._get_strategy(ColumnLoader).create_row_processor(selectcontext, path, mapper, row, adapter)
207
208	elif not self.is_class_level:
209	def new_execute(state, dict_, row, **flags):
210	state.set_callable(self.key, LoadDeferredColumns(state, self.key))
211	else:
212	def new_execute(state, dict_, row, **flags):
213	# reset state on the key so that deferred callables
214	# fire off on next access.
215	state.reset(self.key, dict_)
216
217	if self._should_log_debug:
218	new_execute = self.debug_callable(new_execute, self.logger, None,
219	lambda state, dict_, row, **flags: "set deferred callable on %s" % \
220	mapperutil.state_attribute_str(state, self.key)
221	)
222	return (new_execute, None)
223
224	def init(self):
225	if hasattr(self.parent_property, 'composite_class'):
226	raise NotImplementedError("Deferred loading for composite types not implemented yet")
227	self.columns = self.parent_property.columns
228	self.group = self.parent_property.group
229
230	def init_class_attribute(self, mapper):
231	self.is_class_level = True
232
233	_register_attribute(self, mapper, useobject=False,
234	compare_function=self.columns[0].type.compare_values,
235	copy_function=self.columns[0].type.copy_value,
236	mutable_scalars=self.columns[0].type.is_mutable(),
237	callable_=self._class_level_loader,
238	dont_expire_missing=True
239	)
240
241	def setup_query(self, context, entity, path, adapter, only_load_props=None, **kwargs):
242	if \
243	(self.group is not None and context.attributes.get(('undefer', self.group), False)) or \
244	(only_load_props and self.key in only_load_props):
245
246	self.parent_property._get_strategy(ColumnLoader).setup_query(context, entity, path, adapter, **kwargs)
247
248	def _class_level_loader(self, state):
249	if not mapperutil._state_has_identity(state):
250	return None
251
252	return LoadDeferredColumns(state, self.key)
253
254
255	log.class_logger(DeferredColumnLoader)
256
257	class LoadDeferredColumns(object):
258	"""serializable loader object used by DeferredColumnLoader"""
259
260	def __init__(self, state, key):
261	self.state, self.key = state, key
262
263	def __call__(self):
264	state = self.state
265
266
267	localparent = mapper._state_mapper(state)
268
269	prop = localparent.get_property(self.key)
270	strategy = prop._get_strategy(DeferredColumnLoader)
271
272	if strategy.group:
273	toload = [
274	p.key for p in
275	localparent.iterate_properties
276	if isinstance(p, StrategizedProperty) and
277	isinstance(p.strategy, DeferredColumnLoader) and
278	p.group==strategy.group
279	]
280	else:
281	toload = [self.key]
282
283	# narrow the keys down to just those which have no history
284	group = [k for k in toload if k in state.unmodified]
285
286	if strategy._should_log_debug:
287	strategy.logger.debug(
288	"deferred load %s group %s" %
289	(mapperutil.state_attribute_str(state, self.key), group and ','.join(group) or 'None')
290	)
291
292	session = sessionlib._state_session(state)
293	if session is None:
294	raise sa_exc.UnboundExecutionError(
295	"Parent instance %s is not bound to a Session; "
296	"deferred load operation of attribute '%s' cannot proceed" %
297	(mapperutil.state_str(state), self.key)
298	)
299
300	query = session.query(localparent)
301	ident = state.key[1]
302	query._get(None, ident=ident, only_load_props=group, refresh_state=state)
303	return attributes.ATTR_WAS_SET
304
305	class DeferredOption(StrategizedOption):
306	propagate_to_loaders = True
307
308	def __init__(self, key, defer=False):
309	super(DeferredOption, self).__init__(key)
310	self.defer = defer
311
312	def get_strategy_class(self):
313	if self.defer:
314	return DeferredColumnLoader
315	else:
316	return ColumnLoader
317
318	class UndeferGroupOption(MapperOption):
319	propagate_to_loaders = True
320
321	def __init__(self, group):
322	self.group = group
323	def process_query(self, query):
324	query._attributes[('undefer', self.group)] = True
325
326	class AbstractRelationLoader(LoaderStrategy):
327	"""LoaderStratgies which deal with related objects as opposed to scalars."""
328
329	def init(self):
330	for attr in ['mapper', 'target', 'table', 'uselist']:
331	setattr(self, attr, getattr(self.parent_property, attr))
332
333	def _init_instance_attribute(self, state, callable_=None):
334	if callable_:
335	state.set_callable(self.key, callable_)
336	else:
337	state.initialize(self.key)
338
339	class NoLoader(AbstractRelationLoader):
340	"""Strategize a relation() that doesn't load data automatically."""
341
342	def init_class_attribute(self, mapper):
343	self.is_class_level = True
344
345	_register_attribute(self, mapper,
346	useobject=True,
347	uselist=self.parent_property.uselist,
348	typecallable = self.parent_property.collection_class,
349	)
350
351	def create_row_processor(self, selectcontext, path, mapper, row, adapter):
352	def new_execute(state, dict_, row, **flags):
353	self._init_instance_attribute(state)
354
355	if self._should_log_debug:
356	new_execute = self.debug_callable(new_execute, self.logger, None,
357	lambda state, dict_, row, **flags: "initializing blank scalar/collection on %s" % \
358	mapperutil.state_attribute_str(state, self.key)
359	)
360	return (new_execute, None)
361
362	log.class_logger(NoLoader)
363
364	class LazyLoader(AbstractRelationLoader):
365	"""Strategize a relation() that loads when first accessed."""
366
367	def init(self):
368	super(LazyLoader, self).init()
369	(self.__lazywhere, self.__bind_to_col, self._equated_columns) = self._create_lazy_clause(self.parent_property)
370
371	self.logger.info("%s lazy loading clause %s" % (self, self.__lazywhere))
372
373	# determine if our "lazywhere" clause is the same as the mapper's
374	# get() clause. then we can just use mapper.get()
375	#from sqlalchemy.orm import query
376	self.use_get = not self.uselist and self.mapper._get_clause[0].compare(self.__lazywhere)
377	if self.use_get:
378	self.logger.info("%s will use query.get() to optimize instance loads" % self)
379
380	def init_class_attribute(self, mapper):
381	self.is_class_level = True
382
383	# MANYTOONE currently only needs the "old" value for delete-orphan
384	# cascades. the required _SingleParentValidator will enable active_history
385	# in that case. otherwise we don't need the "old" value during backref operations.
386	_register_attribute(self,
387	mapper,
388	useobject=True,
389	callable_=self._class_level_loader,
390	uselist = self.parent_property.uselist,
391	typecallable = self.parent_property.collection_class,
392	active_history = self.parent_property.direction is not interfaces.MANYTOONE,
393	)
394
395	def lazy_clause(self, state, reverse_direction=False, alias_secondary=False, adapt_source=None):
396	if state is None:
397	return self._lazy_none_clause(reverse_direction, adapt_source=adapt_source)
398
399	if not reverse_direction:
400	(criterion, bind_to_col, rev) = (self.__lazywhere, self.__bind_to_col, self._equated_columns)
401	else:
402	(criterion, bind_to_col, rev) = LazyLoader._create_lazy_clause(self.parent_property, reverse_direction=reverse_direction)
403
404	def visit_bindparam(bindparam):
405	mapper = reverse_direction and self.parent_property.mapper or self.parent_property.parent
406	if bindparam.key in bind_to_col:
407	# use the "committed" (database) version to get query column values
408	# also its a deferred value; so that when used by Query, the committed value is used
409	# after an autoflush occurs
410	o = state.obj() # strong ref
411	bindparam.value = lambda: mapper._get_committed_attr_by_column(o, bind_to_col[bindparam.key])
412
413	if self.parent_property.secondary and alias_secondary:
414	criterion = sql_util.ClauseAdapter(self.parent_property.secondary.alias()).traverse(criterion)
415
416	criterion = visitors.cloned_traverse(criterion, {}, {'bindparam':visit_bindparam})
417	if adapt_source:
418	criterion = adapt_source(criterion)
419	return criterion
420
421	def _lazy_none_clause(self, reverse_direction=False, adapt_source=None):
422	if not reverse_direction:
423	(criterion, bind_to_col, rev) = (self.__lazywhere, self.__bind_to_col, self._equated_columns)
424	else:
425	(criterion, bind_to_col, rev) = LazyLoader._create_lazy_clause(self.parent_property, reverse_direction=reverse_direction)
426
427	def visit_binary(binary):
428	mapper = reverse_direction and self.parent_property.mapper or self.parent_property.parent
429	if isinstance(binary.left, expression._BindParamClause) and binary.left.key in bind_to_col:
430	# reverse order if the NULL is on the left side
431	binary.left = binary.right
432	binary.right = expression.null()
433	binary.operator = operators.is_
434	binary.negate = operators.isnot
435	elif isinstance(binary.right, expression._BindParamClause) and binary.right.key in bind_to_col:
436	binary.right = expression.null()
437	binary.operator = operators.is_
438	binary.negate = operators.isnot
439
440	criterion = visitors.cloned_traverse(criterion, {}, {'binary':visit_binary})
441	if adapt_source:
442	criterion = adapt_source(criterion)
443	return criterion
444
445	def _class_level_loader(self, state):
446	if not mapperutil._state_has_identity(state):
447	return None
448
449	return LoadLazyAttribute(state, self.key)
450
451	def create_row_processor(self, selectcontext, path, mapper, row, adapter):
452	if not self.is_class_level:
453	def new_execute(state, dict_, row, **flags):
454	# we are not the primary manager for this attribute on this class - set up a
455	# per-instance lazyloader, which will override the class-level behavior.
456	# this currently only happens when using a "lazyload" option on a "no load"
457	# attribute - "eager" attributes always have a class-level lazyloader
458	# installed.
459	self._init_instance_attribute(state, callable_=LoadLazyAttribute(state, self.key))
460
461	if self._should_log_debug:
462	new_execute = self.debug_callable(new_execute, self.logger, None,
463	lambda state, dict_, row, **flags: "set instance-level lazy loader on %s" % \
464	mapperutil.state_attribute_str(state,
465	self.key)
466	)
467
468	return (new_execute, None)
469	else:
470	def new_execute(state, dict_, row, **flags):
471	# we are the primary manager for this attribute on this class - reset its
472	# per-instance attribute state, so that the class-level lazy loader is
473	# executed when next referenced on this instance. this is needed in
474	# populate_existing() types of scenarios to reset any existing state.
475	state.reset(self.key, dict_)
476
477	if self._should_log_debug:
478	new_execute = self.debug_callable(new_execute, self.logger, None,
479	lambda state, dict_, row, **flags: "set class-level lazy loader on %s" % \
480	mapperutil.state_attribute_str(state,
481	self.key)
482	)
483
484	return (new_execute, None)
485
486	def _create_lazy_clause(cls, prop, reverse_direction=False):
487	binds = util.column_dict()
488	lookup = util.column_dict()
489	equated_columns = util.column_dict()
490
491	if reverse_direction and not prop.secondaryjoin:
492	for l, r in prop.local_remote_pairs:
493	_list = lookup.setdefault(r, [])
494	_list.append((r, l))
495	equated_columns[l] = r
496	else:
497	for l, r in prop.local_remote_pairs:
498	_list = lookup.setdefault(l, [])
499	_list.append((l, r))
500	equated_columns[r] = l
501
502	def col_to_bind(col):
503	if col in lookup:
504	for tobind, equated in lookup[col]:
505	if equated in binds:
506	return None
507	if col not in binds:
508	binds[col] = sql.bindparam(None, None, type_=col.type)
509	return binds[col]
510	return None
511
512	lazywhere = prop.primaryjoin
513
514	if not prop.secondaryjoin or not reverse_direction:
515	lazywhere = visitors.replacement_traverse(lazywhere, {}, col_to_bind)
516
517	if prop.secondaryjoin is not None:
518	secondaryjoin = prop.secondaryjoin
519	if reverse_direction:
520	secondaryjoin = visitors.replacement_traverse(secondaryjoin, {}, col_to_bind)
521	lazywhere = sql.and_(lazywhere, secondaryjoin)
522
523	bind_to_col = dict((binds[col].key, col) for col in binds)
524
525	return (lazywhere, bind_to_col, equated_columns)
526	_create_lazy_clause = classmethod(_create_lazy_clause)
527
528	log.class_logger(LazyLoader)
529
530	class LoadLazyAttribute(object):
531	"""serializable loader object used by LazyLoader"""
532
533	def __init__(self, state, key):
534	self.state, self.key = state, key
535
536	def __getstate__(self):
537	return (self.state, self.key)
538
539	def __setstate__(self, state):
540	self.state, self.key = state
541
542	def __call__(self):
543	state = self.state
544
545	instance_mapper = mapper._state_mapper(state)
546	prop = instance_mapper.get_property(self.key)
547	strategy = prop._get_strategy(LazyLoader)
548
549	if strategy._should_log_debug:
550	strategy.logger.debug("loading %s" % mapperutil.state_attribute_str(state, self.key))
551
552	session = sessionlib._state_session(state)
553	if session is None:
554	raise sa_exc.UnboundExecutionError(
555	"Parent instance %s is not bound to a Session; "
556	"lazy load operation of attribute '%s' cannot proceed" %
557	(mapperutil.state_str(state), self.key)
558	)
559
560	q = session.query(prop.mapper)._adapt_all_clauses()
561
562	if state.load_path:
563	q = q._with_current_path(state.load_path + (self.key,))
564
565	# if we have a simple primary key load, use mapper.get()
566	# to possibly save a DB round trip
567	if strategy.use_get:
568	ident = []
569	allnulls = True
570	for primary_key in prop.mapper.primary_key:
571	val = instance_mapper._get_committed_state_attr_by_column(state, strategy._equated_columns[primary_key])
572	allnulls = allnulls and val is None
573	ident.append(val)
574	if allnulls:
575	return None
576	if state.load_options:
577	q = q._conditional_options(*state.load_options)
578	return q.get(ident)
579
580	if prop.order_by:
581	q = q.order_by(*util.to_list(prop.order_by))
582
583	if state.load_options:
584	q = q._conditional_options(*state.load_options)
585	q = q.filter(strategy.lazy_clause(state))
586
587	result = q.all()
588	if strategy.uselist:
589	return result
590	else:
591	if result:
592	return result[0]
593	else:
594	return None
595
596	class EagerLoader(AbstractRelationLoader):
597	"""Strategize a relation() that loads within the process of the parent object being selected."""
598
599	def init(self):
600	super(EagerLoader, self).init()
601	self.join_depth = self.parent_property.join_depth
602
603	def init_class_attribute(self, mapper):
604	self.parent_property._get_strategy(LazyLoader).init_class_attribute(mapper)
605
606	def setup_query(self, context, entity, path, adapter, column_collection=None, parentmapper=None, **kwargs):
607	"""Add a left outer join to the statement thats being constructed."""
608
609	if not context.enable_eagerloads:
610	return
611
612	path = path + (self.key,)
613
614	# check for user-defined eager alias
615	if ("user_defined_eager_row_processor", path) in context.attributes:
616	clauses = context.attributes[("user_defined_eager_row_processor", path)]
617
618	adapter = entity._get_entity_clauses(context.query, context)
619	if adapter and clauses:
620	context.attributes[("user_defined_eager_row_processor", path)] = clauses = clauses.wrap(adapter)
621	elif adapter:
622	context.attributes[("user_defined_eager_row_processor", path)] = clauses = adapter
623
624	add_to_collection = context.primary_columns
625
626	else:
627	clauses = self._create_eager_join(context, entity, path, adapter, parentmapper)
628	if not clauses:
629	return
630
631	context.attributes[("eager_row_processor", path)] = clauses
632
633	add_to_collection = context.secondary_columns
634
635	for value in self.mapper._iterate_polymorphic_properties():
636	value.setup(context, entity, path + (self.mapper.base_mapper,), clauses, parentmapper=self.mapper, column_collection=add_to_collection)
637
638	def _create_eager_join(self, context, entity, path, adapter, parentmapper):
639	# check for join_depth or basic recursion,
640	# if the current path was not explicitly stated as
641	# a desired "loaderstrategy" (i.e. via query.options())
642	if ("loaderstrategy", path) not in context.attributes:
643	if self.join_depth:
644	if len(path) / 2 > self.join_depth:
645	return
646	else:
647	if self.mapper.base_mapper in path:
648	return
649
650	if parentmapper is None:
651	localparent = entity.mapper
652	else:
653	localparent = parentmapper
654
655	# whether or not the Query will wrap the selectable in a subquery,
656	# and then attach eager load joins to that (i.e., in the case of LIMIT/OFFSET etc.)
657	should_nest_selectable = context.query._should_nest_selectable
658
659	if entity in context.eager_joins:
660	entity_key, default_towrap = entity, entity.selectable
661
662	elif should_nest_selectable or not context.from_clause:
663	# if no from_clause, or a subquery is going to be generated,
664	# store eager joins per _MappedEntity; Query._compile_context will
665	# add them as separate selectables to the select(), or splice them together
666	# after the subquery is generated
667	entity_key, default_towrap = entity, entity.selectable
668	else:
669	index, clause = sql_util.find_join_source(context.from_clause, entity.selectable)
670	if clause:
671	# join to an existing FROM clause on the query.
672	# key it to its list index in the eager_joins dict.
673	# Query._compile_context will adapt as needed and append to the
674	# FROM clause of the select().
675	entity_key, default_towrap = index, clause
676	else:
677	# if no from_clause to join to,
678	# store eager joins per _MappedEntity
679	entity_key, default_towrap = entity, entity.selectable
680
681	towrap = context.eager_joins.setdefault(entity_key, default_towrap)
682
683	# create AliasedClauses object to build up the eager query.
684	clauses = mapperutil.ORMAdapter(mapperutil.AliasedClass(self.mapper),
685	equivalents=self.mapper._equivalent_columns, adapt_required=True)
686
687	join_to_left = False
688	if adapter:
689	if getattr(adapter, 'aliased_class', None):
690	onclause = getattr(adapter.aliased_class, self.key, self.parent_property)
691	else:
692	onclause = getattr(mapperutil.AliasedClass(self.parent, adapter.selectable), self.key, self.parent_property)
693
694	if onclause is self.parent_property:
695	# TODO: this is a temporary hack to account for polymorphic eager loads where
696	# the eagerload is referencing via of_type().
697	join_to_left = True
698	else:
699	onclause = self.parent_property
700
701	context.eager_joins[entity_key] = eagerjoin = mapperutil.outerjoin(towrap, clauses.aliased_class, onclause, join_to_left=join_to_left)
702
703	# send a hint to the Query as to where it may "splice" this join
704	eagerjoin.stop_on = entity.selectable
705
706	if not self.parent_property.secondary and context.query._should_nest_selectable and not parentmapper:
707	# for parentclause that is the non-eager end of the join,
708	# ensure all the parent cols in the primaryjoin are actually in the
709	# columns clause (i.e. are not deferred), so that aliasing applied by the Query propagates
710	# those columns outward. This has the effect of "undefering" those columns.
711	for col in sql_util.find_columns(self.parent_property.primaryjoin):
712	if localparent.mapped_table.c.contains_column(col):
713	if adapter:
714	col = adapter.columns[col]
715	context.primary_columns.append(col)
716
717	if self.parent_property.order_by:
718	context.eager_order_by += eagerjoin._target_adapter.copy_and_process(util.to_list(self.parent_property.order_by))
719
720	return clauses
721
722	def _create_eager_adapter(self, context, row, adapter, path):
723	if ("user_defined_eager_row_processor", path) in context.attributes:
724	decorator = context.attributes[("user_defined_eager_row_processor", path)]
725	# user defined eagerloads are part of the "primary" portion of the load.
726	# the adapters applied to the Query should be honored.
727	if context.adapter and decorator:
728	decorator = decorator.wrap(context.adapter)
729	elif context.adapter:
730	decorator = context.adapter
731	elif ("eager_row_processor", path) in context.attributes:
732	decorator = context.attributes[("eager_row_processor", path)]
733	else:
734	if self._should_log_debug:
735	self.logger.debug("Could not locate aliased clauses for key: " + str(path))
736	return False
737
738	try:
739	identity_key = self.mapper.identity_key_from_row(row, decorator)
740	return decorator
741	except KeyError, k:
742	# no identity key - dont return a row processor, will cause a degrade to lazy
743	if self._should_log_debug:
744	self.logger.debug("could not locate identity key from row; missing column '%s'" % k)
745	return False
746
747	def create_row_processor(self, context, path, mapper, row, adapter):
748	path = path + (self.key,)
749
750	eager_adapter = self._create_eager_adapter(context, row, adapter, path)
751
752	if eager_adapter is not False:
753	key = self.key
754	_instance = self.mapper._instance_processor(context, path + (self.mapper.base_mapper,), eager_adapter)
755
756	if not self.uselist:
757	def execute(state, dict_, row, isnew, **flags):
758	if isnew:
759	# set a scalar object instance directly on the
760	# parent object, bypassing InstrumentedAttribute
761	# event handlers.
762	dict_[key] = _instance(row, None)
763	else:
764	# call _instance on the row, even though the object has been created,
765	# so that we further descend into properties
766	_instance(row, None)
767	else:
768	def execute(state, dict_, row, isnew, **flags):
769	if isnew or (state, key) not in context.attributes:
770	# appender_key can be absent from context.attributes with isnew=False
771	# when self-referential eager loading is used; the same instance may be present
772	# in two distinct sets of result columns
773
774	collection = attributes.init_state_collection(state, dict_, key)
775	appender = util.UniqueAppender(collection, 'append_without_event')
776
777	context.attributes[(state, key)] = appender
778
779	result_list = context.attributes[(state, key)]
780
781	_instance(row, result_list)
782
783	if self._should_log_debug:
784	execute = self.debug_callable(execute, self.logger,
785	"%s returning eager instance loader" % self,
786	lambda state, dict_, row, isnew, **flags: "%s eagerload %s" % \
787	(self,
788	self.uselist and "scalar attribute"
789	or "collection")
790	)
791
792	return (execute, execute)
793	else:
794	if self._should_log_debug:
795	self.logger.debug("%s degrading to lazy loader" % self)
796	return self.parent_property._get_strategy(LazyLoader).create_row_processor(context, path, mapper, row, adapter)
797
798	log.class_logger(EagerLoader)
799
800	class EagerLazyOption(StrategizedOption):
801
802	def __init__(self, key, lazy=True, chained=False, mapper=None, propagate_to_loaders=True):
803	super(EagerLazyOption, self).__init__(key, mapper)
804	self.lazy = lazy
805	self.chained = chained
806	self.propagate_to_loaders = propagate_to_loaders
807
808	def is_chained(self):
809	return not self.lazy and self.chained
810
811	def get_strategy_class(self):
812	if self.lazy:
813	return LazyLoader
814	elif self.lazy is False:
815	return EagerLoader
816	elif self.lazy is None:
817	return NoLoader
818
819	class LoadEagerFromAliasOption(PropertyOption):
820
821	def __init__(self, key, alias=None):
822	super(LoadEagerFromAliasOption, self).__init__(key)
823	if alias:
824	if not isinstance(alias, basestring):
825	m, alias, is_aliased_class = mapperutil._entity_info(alias)
826	self.alias = alias
827
828	def process_query_property(self, query, paths, mappers):
829	if self.alias:
830	if isinstance(self.alias, basestring):
831	mapper = mappers[-1]
832	(root_mapper, propname) = paths[-1][-2:]
833	prop = mapper.get_property(propname, resolve_synonyms=True)
834	self.alias = prop.target.alias(self.alias)
835	query._attributes[("user_defined_eager_row_processor", paths[-1])] = sql_util.ColumnAdapter(self.alias)
836	else:
837	(root_mapper, propname) = paths[-1][-2:]
838	mapper = mappers[-1]
839	prop = mapper.get_property(propname, resolve_synonyms=True)
840	adapter = query._polymorphic_adapters.get(prop.mapper, None)
841	query._attributes[("user_defined_eager_row_processor", paths[-1])] = adapter
842
843	class _SingleParentValidator(interfaces.AttributeExtension):
844	def __init__(self, prop):
845	self.prop = prop
846
847	def _do_check(self, state, value, oldvalue, initiator):
848	if value is not None:
849	hasparent = initiator.hasparent(attributes.instance_state(value))
850	if hasparent and oldvalue is not value:
851	raise sa_exc.InvalidRequestError("Instance %s is already associated with an instance "
852	"of %s via its %s attribute, and is only allowed a single parent." %
853	(mapperutil.instance_str(value), state.class_, self.prop)
854	)
855	return value
856
857	def append(self, state, value, initiator):
858	return self._do_check(state, value, None, initiator)
859
860	def set(self, state, value, oldvalue, initiator):
861	return self._do_check(state, value, oldvalue, initiator)
862
863

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