name : strategy_options.py # Copyright (C) 2005-2021 the SQLAlchemy authors and contributors # <see AUTHORS file> # # This module is part of SQLAlchemy and is released under # the MIT License: http://www.opensource.org/licenses/mit-license.php """ """ from . import util as orm_util from .attributes import QueryableAttribute from .base import _class_to_mapper from .base import _is_aliased_class from .base import _is_mapped_class from .base import InspectionAttr from .interfaces import MapperOption from .interfaces import MapperProperty from .interfaces import PropComparator from .path_registry import _DEFAULT_TOKEN from .path_registry import _WILDCARD_TOKEN from .path_registry import PathRegistry from .path_registry import TokenRegistry from .util import _orm_full_deannotate from .. import exc as sa_exc from .. import inspect from .. import util from ..sql import expression as sql_expr from ..sql.base import _generative from ..sql.base import Generative class Load(Generative, MapperOption): """Represents loader options which modify the state of a :class:`_query.Query` in order to affect how various mapped attributes are loaded. The :class:`_orm.Load` object is in most cases used implicitly behind the scenes when one makes use of a query option like :func:`_orm.joinedload`, :func:`.defer`, or similar. However, the :class:`_orm.Load` object can also be used directly, and in some cases can be useful. To use :class:`_orm.Load` directly, instantiate it with the target mapped class as the argument. This style of usage is useful when dealing with a :class:`_query.Query` that has multiple entities:: myopt = Load(MyClass).joinedload("widgets") The above ``myopt`` can now be used with :meth:`_query.Query.options`, where it will only take effect for the ``MyClass`` entity:: session.query(MyClass, MyOtherClass).options(myopt) One case where :class:`_orm.Load` is useful as public API is when specifying "wildcard" options that only take effect for a certain class:: session.query(Order).options(Load(Order).lazyload('*')) Above, all relationships on ``Order`` will be lazy-loaded, but other attributes on those descendant objects will load using their normal loader strategy. .. seealso:: :ref:`deferred_options` :ref:`deferred_loading_w_multiple` :ref:`relationship_loader_options` """ def __init__(self, entity): insp = inspect(entity) self.path = insp._path_registry # note that this .context is shared among all descendant # Load objects self.context = util.OrderedDict() self.local_opts = {} self.is_class_strategy = False @classmethod def for_existing_path(cls, path): load = cls.__new__(cls) load.path = path load.context = {} load.local_opts = {} load._of_type = None return load def _generate_cache_key(self, path): if path.path[0].is_aliased_class: return False serialized = [] for (key, loader_path), obj in self.context.items(): if key != "loader": continue for local_elem, obj_elem in zip(self.path.path, loader_path): if local_elem is not obj_elem: break else: endpoint = obj._of_type or obj.path.path[-1] chopped = self._chop_path(loader_path, path) if ( # means loader_path and path are unrelated, # this does not need to be part of a cache key chopped is None ) or ( # means no additional path with loader_path + path # and the endpoint isn't using of_type so isn't modified # into an alias or other unsafe entity not chopped and not obj._of_type ): continue serialized_path = [] for token in chopped: if isinstance(token, util.string_types): serialized_path.append(token) elif token.is_aliased_class: return False elif token.is_property: serialized_path.append(token.key) else: assert token.is_mapper serialized_path.append(token.class_) if not serialized_path or endpoint != serialized_path[-1]: if endpoint.is_mapper: serialized_path.append(endpoint.class_) elif endpoint.is_aliased_class: return False serialized.append( ( tuple(serialized_path) + (obj.strategy or ()) + ( tuple( [ (key, obj.local_opts[key]) for key in sorted(obj.local_opts) ] ) if obj.local_opts else () ) ) ) if not serialized: return None else: return tuple(serialized) def _generate(self): cloned = super(Load, self)._generate() cloned.local_opts = {} return cloned is_opts_only = False is_class_strategy = False strategy = None propagate_to_loaders = False _of_type = None def process_query(self, query): self._process(query, True) def process_query_conditionally(self, query): self._process(query, False) def _process(self, query, raiseerr): current_path = query._current_path if current_path: for (token, start_path), loader in self.context.items(): chopped_start_path = self._chop_path(start_path, current_path) if chopped_start_path is not None: query._attributes[(token, chopped_start_path)] = loader else: query._attributes.update(self.context) def _generate_path( self, path, attr, for_strategy, wildcard_key, raiseerr=True ): existing_of_type = self._of_type self._of_type = None if raiseerr and not path.has_entity: if isinstance(path, TokenRegistry): raise sa_exc.ArgumentError( "Wildcard token cannot be followed by another entity" ) else: raise sa_exc.ArgumentError( "Mapped attribute '%s' does not " "refer to a mapped entity" % (path.prop,) ) if isinstance(attr, util.string_types): default_token = attr.endswith(_DEFAULT_TOKEN) attr_str_name = attr if attr.endswith(_WILDCARD_TOKEN) or default_token: if default_token: self.propagate_to_loaders = False if wildcard_key: attr = "%s:%s" % (wildcard_key, attr) # TODO: AliasedInsp inside the path for of_type is not # working for a with_polymorphic entity because the # relationship loaders don't render the with_poly into the # path. See #4469 which will try to improve this if existing_of_type and not existing_of_type.is_aliased_class: path = path.parent[existing_of_type] path = path.token(attr) self.path = path return path if existing_of_type: ent = inspect(existing_of_type) else: ent = path.entity try: # use getattr on the class to work around # synonyms, hybrids, etc. attr = getattr(ent.class_, attr) except AttributeError as err: if raiseerr: util.raise_( sa_exc.ArgumentError( 'Can\'t find property named "%s" on ' "%s in this Query." % (attr, ent) ), replace_context=err, ) else: return None else: try: attr = found_property = attr.property except AttributeError as ae: if not isinstance(attr, MapperProperty): util.raise_( sa_exc.ArgumentError( 'Expected attribute "%s" on %s to be a ' "mapped attribute; " "instead got %s object." % (attr_str_name, ent, type(attr)) ), replace_context=ae, ) else: raise path = path[attr] elif _is_mapped_class(attr): # TODO: this does not appear to be a valid codepath. "attr" # would never be a mapper. This block is present in 1.2 # as well however does not seem to be accessed in any tests. if not orm_util._entity_corresponds_to_use_path_impl( attr.parent, path[-1] ): if raiseerr: raise sa_exc.ArgumentError( "Attribute '%s' does not " "link from element '%s'" % (attr, path.entity) ) else: return None else: prop = found_property = attr.property if not orm_util._entity_corresponds_to_use_path_impl( attr.parent, path[-1] ): if raiseerr: raise sa_exc.ArgumentError( 'Attribute "%s" does not ' 'link from element "%s".%s' % ( attr, path.entity, ( " Did you mean to use " "%s.of_type(%s)?" % (path[-2], attr.class_.__name__) if len(path) > 1 and path.entity.is_mapper and attr.parent.is_aliased_class else "" ), ) ) else: return None if getattr(attr, "_of_type", None): ac = attr._of_type ext_info = of_type_info = inspect(ac) existing = path.entity_path[prop].get( self.context, "path_with_polymorphic" ) if not ext_info.is_aliased_class: ac = orm_util.with_polymorphic( ext_info.mapper.base_mapper, ext_info.mapper, aliased=True, _use_mapper_path=True, _existing_alias=inspect(existing) if existing is not None else None, ) ext_info = inspect(ac) path.entity_path[prop].set( self.context, "path_with_polymorphic", ac ) path = path[prop][ext_info] self._of_type = of_type_info else: path = path[prop] if for_strategy is not None: found_property._get_strategy(for_strategy) if path.has_entity: path = path.entity_path self.path = path return path def __str__(self): return "Load(strategy=%r)" % (self.strategy,) def _coerce_strat(self, strategy): if strategy is not None: strategy = tuple(sorted(strategy.items())) return strategy def _apply_to_parent(self, parent, applied, bound): raise NotImplementedError( "Only 'unbound' loader options may be used with the " "Load.options() method" ) @_generative def options(self, *opts): r"""Apply a series of options as sub-options to this :class:`_orm.Load` object. E.g.:: query = session.query(Author) query = query.options( joinedload(Author.book).options( load_only("summary", "excerpt"), joinedload(Book.citations).options( joinedload(Citation.author) ) ) ) :param \*opts: A series of loader option objects (ultimately :class:`_orm.Load` objects) which should be applied to the path specified by this :class:`_orm.Load` object. .. versionadded:: 1.3.6 .. seealso:: :func:`.defaultload` :ref:`relationship_loader_options` :ref:`deferred_loading_w_multiple` """ apply_cache = {} bound = not isinstance(self, _UnboundLoad) if bound: raise NotImplementedError( "The options() method is currently only supported " "for 'unbound' loader options" ) for opt in opts: opt._apply_to_parent(self, apply_cache, bound) @_generative def set_relationship_strategy( self, attr, strategy, propagate_to_loaders=True ): strategy = self._coerce_strat(strategy) self.propagate_to_loaders = propagate_to_loaders cloned = self._clone_for_bind_strategy(attr, strategy, "relationship") self.path = cloned.path self._of_type = cloned._of_type cloned.is_class_strategy = self.is_class_strategy = False self.propagate_to_loaders = cloned.propagate_to_loaders @_generative def set_column_strategy(self, attrs, strategy, opts=None, opts_only=False): strategy = self._coerce_strat(strategy) self.is_class_strategy = False for attr in attrs: cloned = self._clone_for_bind_strategy( attr, strategy, "column", opts_only=opts_only, opts=opts ) cloned.propagate_to_loaders = True @_generative def set_generic_strategy(self, attrs, strategy): strategy = self._coerce_strat(strategy) for attr in attrs: cloned = self._clone_for_bind_strategy(attr, strategy, None) cloned.propagate_to_loaders = True @_generative def set_class_strategy(self, strategy, opts): strategy = self._coerce_strat(strategy) cloned = self._clone_for_bind_strategy(None, strategy, None) cloned.is_class_strategy = True cloned.propagate_to_loaders = True cloned.local_opts.update(opts) def _clone_for_bind_strategy( self, attr, strategy, wildcard_key, opts_only=False, opts=None ): """Create an anonymous clone of the Load/_UnboundLoad that is suitable to be placed in the context / _to_bind collection of this Load object. The clone will then lose references to context/_to_bind in order to not create reference cycles. """ cloned = self._generate() cloned._generate_path(self.path, attr, strategy, wildcard_key) cloned.strategy = strategy cloned.local_opts = self.local_opts if opts: cloned.local_opts.update(opts) if opts_only: cloned.is_opts_only = True if strategy or cloned.is_opts_only: cloned._set_path_strategy() return cloned def _set_for_path(self, context, path, replace=True, merge_opts=False): if merge_opts or not replace: existing = path.get(self.context, "loader") if existing: if merge_opts: existing.local_opts.update(self.local_opts) else: path.set(context, "loader", self) else: existing = path.get(self.context, "loader") path.set(context, "loader", self) if existing and existing.is_opts_only: self.local_opts.update(existing.local_opts) def _set_path_strategy(self): if not self.is_class_strategy and self.path.has_entity: effective_path = self.path.parent else: effective_path = self.path if effective_path.is_token: for path in effective_path.generate_for_superclasses(): self._set_for_path( self.context, path, replace=True, merge_opts=self.is_opts_only, ) else: self._set_for_path( self.context, effective_path, replace=True, merge_opts=self.is_opts_only, ) # remove cycles; _set_path_strategy is always invoked on an # anonymous clone of the Load / UnboundLoad object since #5056 self.context = None def __getstate__(self): d = self.__dict__.copy() if d["context"] is not None: d["context"] = PathRegistry.serialize_context_dict( d["context"], ("loader",) ) d["path"] = self.path.serialize() return d def __setstate__(self, state): self.__dict__.update(state) self.path = PathRegistry.deserialize(self.path) if self.context is not None: self.context = PathRegistry.deserialize_context_dict(self.context) def _chop_path(self, to_chop, path): i = -1 for i, (c_token, p_token) in enumerate(zip(to_chop, path.path)): if isinstance(c_token, util.string_types): # TODO: this is approximated from the _UnboundLoad # version and probably has issues, not fully covered. if i == 0 and c_token.endswith(":" + _DEFAULT_TOKEN): return to_chop elif ( c_token != "relationship:%s" % (_WILDCARD_TOKEN,) and c_token != p_token.key ): return None if c_token is p_token: continue elif ( isinstance(c_token, InspectionAttr) and c_token.is_mapper and p_token.is_mapper and c_token.isa(p_token) ): continue else: return None return to_chop[i + 1 :] class _UnboundLoad(Load): """Represent a loader option that isn't tied to a root entity. The loader option will produce an entity-linked :class:`_orm.Load` object when it is passed :meth:`_query.Query.options`. This provides compatibility with the traditional system of freestanding options, e.g. ``joinedload('x.y.z')``. """ def __init__(self): self.path = () self._to_bind = [] self.local_opts = {} _is_chain_link = False def _generate_cache_key(self, path): serialized = () for val in self._to_bind: for local_elem, val_elem in zip(self.path, val.path): if local_elem is not val_elem: break else: opt = val._bind_loader([path.path[0]], None, None, False) if opt: c_key = opt._generate_cache_key(path) if c_key is False: return False elif c_key: serialized += c_key if not serialized: return None else: return serialized def _set_path_strategy(self): self._to_bind.append(self) # remove cycles; _set_path_strategy is always invoked on an # anonymous clone of the Load / UnboundLoad object since #5056 self._to_bind = None def _apply_to_parent(self, parent, applied, bound, to_bind=None): if self in applied: return applied[self] if to_bind is None: to_bind = self._to_bind cloned = self._generate() applied[self] = cloned cloned.strategy = self.strategy if self.path: attr = self.path[-1] if isinstance(attr, util.string_types) and attr.endswith( _DEFAULT_TOKEN ): attr = attr.split(":")[0] + ":" + _WILDCARD_TOKEN cloned._generate_path( parent.path + self.path[0:-1], attr, self.strategy, None ) # these assertions can go away once the "sub options" API is # mature assert cloned.propagate_to_loaders == self.propagate_to_loaders assert cloned.is_class_strategy == self.is_class_strategy assert cloned.is_opts_only == self.is_opts_only new_to_bind = { elem._apply_to_parent(parent, applied, bound, to_bind) for elem in to_bind } cloned._to_bind = parent._to_bind cloned._to_bind.extend(new_to_bind) cloned.local_opts.update(self.local_opts) return cloned def _generate_path(self, path, attr, for_strategy, wildcard_key): if ( wildcard_key and isinstance(attr, util.string_types) and attr in (_WILDCARD_TOKEN, _DEFAULT_TOKEN) ): if attr == _DEFAULT_TOKEN: self.propagate_to_loaders = False attr = "%s:%s" % (wildcard_key, attr) if path and _is_mapped_class(path[-1]) and not self.is_class_strategy: path = path[0:-1] if attr: path = path + (attr,) self.path = path return path def __getstate__(self): d = self.__dict__.copy() d["path"] = self._serialize_path(self.path, filter_aliased_class=True) return d def __setstate__(self, state): ret = [] for key in state["path"]: if isinstance(key, tuple): if len(key) == 2: # support legacy cls, propkey = key of_type = None else: cls, propkey, of_type = key prop = getattr(cls, propkey) if of_type: prop = prop.of_type(of_type) ret.append(prop) else: ret.append(key) state["path"] = tuple(ret) self.__dict__ = state def _process(self, query, raiseerr): dedupes = query._attributes["_unbound_load_dedupes"] for val in self._to_bind: if val not in dedupes: dedupes.add(val) val._bind_loader( [ent.entity_zero for ent in query._mapper_entities], query._current_path, query._attributes, raiseerr, ) @classmethod def _from_keys(cls, meth, keys, chained, kw): opt = _UnboundLoad() def _split_key(key): if isinstance(key, util.string_types): # coerce fooload('*') into "default loader strategy" if key == _WILDCARD_TOKEN: return (_DEFAULT_TOKEN,) # coerce fooload(".*") into "wildcard on default entity" elif key.startswith("." + _WILDCARD_TOKEN): key = key[1:] return key.split(".") else: return (key,) all_tokens = [token for key in keys for token in _split_key(key)] for token in all_tokens[0:-1]: # set _is_chain_link first so that clones of the # object also inherit this flag opt._is_chain_link = True if chained: opt = meth(opt, token, **kw) else: opt = opt.defaultload(token) opt = meth(opt, all_tokens[-1], **kw) opt._is_chain_link = False return opt def _chop_path(self, to_chop, path): i = -1 for i, (c_token, (p_entity, p_prop)) in enumerate( zip(to_chop, path.pairs()) ): if isinstance(c_token, util.string_types): if i == 0 and c_token.endswith(":" + _DEFAULT_TOKEN): return to_chop elif ( c_token != "relationship:%s" % (_WILDCARD_TOKEN,) and c_token != p_prop.key ): return None elif isinstance(c_token, PropComparator): if c_token.property is not p_prop or ( c_token._parententity is not p_entity and ( not c_token._parententity.is_mapper or not c_token._parententity.isa(p_entity) ) ): return None else: i += 1 return to_chop[i:] def _serialize_path(self, path, filter_aliased_class=False): ret = [] for token in path: if isinstance(token, QueryableAttribute): if ( filter_aliased_class and token._of_type and inspect(token._of_type).is_aliased_class ): ret.append((token._parentmapper.class_, token.key, None)) else: ret.append( (token._parentmapper.class_, token.key, token._of_type) ) elif isinstance(token, PropComparator): ret.append((token._parentmapper.class_, token.key, None)) else: ret.append(token) return ret def _bind_loader(self, entities, current_path, context, raiseerr): """Convert from an _UnboundLoad() object into a Load() object. The _UnboundLoad() uses an informal "path" and does not necessarily refer to a lead entity as it may use string tokens. The Load() OTOH refers to a complete path. This method reconciles from a given Query into a Load. Example:: query = session.query(User).options( joinedload("orders").joinedload("items")) The above options will be an _UnboundLoad object along the lines of (note this is not the exact API of _UnboundLoad):: _UnboundLoad( _to_bind=[ _UnboundLoad(["orders"], {"lazy": "joined"}), _UnboundLoad(["orders", "items"], {"lazy": "joined"}), ] ) After this method, we get something more like this (again this is not exact API):: Load( User, (User, User.orders.property)) Load( User, (User, User.orders.property, Order, Order.items.property)) """ start_path = self.path if self.is_class_strategy and current_path: start_path += (entities[0],) # _current_path implies we're in a # secondary load with an existing path if current_path: start_path = self._chop_path(start_path, current_path) if not start_path: return None # look at the first token and try to locate within the Query # what entity we are referring towards. token = start_path[0] if isinstance(token, util.string_types): entity = self._find_entity_basestring(entities, token, raiseerr) elif isinstance(token, PropComparator): prop = token.property entity = self._find_entity_prop_comparator( entities, prop, token._parententity, raiseerr ) elif self.is_class_strategy and _is_mapped_class(token): entity = inspect(token) if entity not in entities: entity = None else: raise sa_exc.ArgumentError( "mapper option expects " "string key or list of attributes" ) if not entity: return path_element = entity # transfer our entity-less state into a Load() object # with a real entity path. Start with the lead entity # we just located, then go through the rest of our path # tokens and populate into the Load(). loader = Load(path_element) if context is not None: loader.context = context else: context = loader.context loader.strategy = self.strategy loader.is_opts_only = self.is_opts_only loader.is_class_strategy = self.is_class_strategy path = loader.path if not loader.is_class_strategy: for idx, token in enumerate(start_path): if not loader._generate_path( loader.path, token, self.strategy if idx == len(start_path) - 1 else None, None, raiseerr, ): return loader.local_opts.update(self.local_opts) if not loader.is_class_strategy and loader.path.has_entity: effective_path = loader.path.parent else: effective_path = loader.path # prioritize "first class" options over those # that were "links in the chain", e.g. "x" and "y" in # someload("x.y.z") versus someload("x") / someload("x.y") if effective_path.is_token: for path in effective_path.generate_for_superclasses(): loader._set_for_path( context, path, replace=not self._is_chain_link, merge_opts=self.is_opts_only, ) else: loader._set_for_path( context, effective_path, replace=not self._is_chain_link, merge_opts=self.is_opts_only, ) return loader def _find_entity_prop_comparator(self, entities, prop, mapper, raiseerr): if _is_aliased_class(mapper): searchfor = mapper else: searchfor = _class_to_mapper(mapper) for ent in entities: if orm_util._entity_corresponds_to(ent, searchfor): return ent else: if raiseerr: if not list(entities): raise sa_exc.ArgumentError( "Query has only expression-based entities, " 'which do not apply to %s "%s"' % (util.clsname_as_plain_name(type(prop)), prop) ) else: raise sa_exc.ArgumentError( 'Mapped attribute "%s" does not apply to any of the ' "root entities in this query, e.g. %s. Please " "specify the full path " "from one of the root entities to the target " "attribute. " % (prop, ", ".join(str(x) for x in entities)) ) else: return None def _find_entity_basestring(self, entities, token, raiseerr): if token.endswith(":" + _WILDCARD_TOKEN): if len(list(entities)) != 1: if raiseerr: raise sa_exc.ArgumentError( "Can't apply wildcard ('*') or load_only() " "loader option to multiple entities %s. Specify " "loader options for each entity individually, such " "as %s." % ( ", ".join(str(ent) for ent in entities), ", ".join( "Load(%s).some_option('*')" % ent for ent in entities ), ) ) elif token.endswith(_DEFAULT_TOKEN): raiseerr = False for ent in entities: # return only the first _MapperEntity when searching # based on string prop name. Ideally object # attributes are used to specify more exactly. return ent else: if raiseerr: raise sa_exc.ArgumentError( "Query has only expression-based entities - " 'can\'t find property named "%s".' % (token,) ) else: return None class loader_option(object): def __init__(self): pass def __call__(self, fn): self.name = name = fn.__name__ self.fn = fn if hasattr(Load, name): raise TypeError("Load class already has a %s method." % (name)) setattr(Load, name, fn) return self def _add_unbound_fn(self, fn): self._unbound_fn = fn fn_doc = self.fn.__doc__ self.fn.__doc__ = """Produce a new :class:`_orm.Load` object with the :func:`_orm.%(name)s` option applied. See :func:`_orm.%(name)s` for usage examples. """ % { "name": self.name } fn.__doc__ = fn_doc return self def _add_unbound_all_fn(self, fn): fn.__doc__ = """Produce a standalone "all" option for :func:`_orm.%(name)s`. .. deprecated:: 0.9 The :func:`_orm.%(name)s_all` function is deprecated, and will be removed in a future release. Please use method chaining with :func:`_orm.%(name)s` instead, as in:: session.query(MyClass).options( %(name)s("someattribute").%(name)s("anotherattribute") ) """ % { "name": self.name } fn = util.deprecated( "0.9", "The :func:`.%(name)s_all` function is deprecated, and will be " "removed in a future release. Please use method chaining with " ":func:`.%(name)s` instead" % {"name": self.name}, add_deprecation_to_docstring=False, )(fn) self._unbound_all_fn = fn return self @loader_option() def contains_eager(loadopt, attr, alias=None): r"""Indicate that the given attribute should be eagerly loaded from columns stated manually in the query. This function is part of the :class:`_orm.Load` interface and supports both method-chained and standalone operation. The option is used in conjunction with an explicit join that loads the desired rows, i.e.:: sess.query(Order).\ join(Order.user).\ options(contains_eager(Order.user)) The above query would join from the ``Order`` entity to its related ``User`` entity, and the returned ``Order`` objects would have the ``Order.user`` attribute pre-populated. It may also be used for customizing the entries in an eagerly loaded collection; queries will normally want to use the :meth:`_query.Query.populate_existing` method assuming the primary collection of parent objects may already have been loaded:: sess.query(User).\ join(User.addresses).\ filter(Address.email_address.like('%@aol.com')).\ options(contains_eager(User.addresses)).\ populate_existing() See the section :ref:`contains_eager` for complete usage details. .. seealso:: :ref:`loading_toplevel` :ref:`contains_eager` """ if alias is not None: if not isinstance(alias, str): info = inspect(alias) alias = info.selectable elif getattr(attr, "_of_type", None): ot = inspect(attr._of_type) alias = ot.selectable cloned = loadopt.set_relationship_strategy( attr, {"lazy": "joined"}, propagate_to_loaders=False ) cloned.local_opts["eager_from_alias"] = alias return cloned @contains_eager._add_unbound_fn def contains_eager(*keys, **kw): return _UnboundLoad()._from_keys( _UnboundLoad.contains_eager, keys, True, kw ) @loader_option() def load_only(loadopt, *attrs): """Indicate that for a particular entity, only the given list of column-based attribute names should be loaded; all others will be deferred. This function is part of the :class:`_orm.Load` interface and supports both method-chained and standalone operation. Example - given a class ``User``, load only the ``name`` and ``fullname`` attributes:: session.query(User).options(load_only("name", "fullname")) Example - given a relationship ``User.addresses -> Address``, specify subquery loading for the ``User.addresses`` collection, but on each ``Address`` object load only the ``email_address`` attribute:: session.query(User).options( subqueryload("addresses").load_only("email_address") ) For a :class:`_query.Query` that has multiple entities, the lead entity can be specifically referred to using the :class:`_orm.Load` constructor:: session.query(User, Address).join(User.addresses).options( Load(User).load_only("name", "fullname"), Load(Address).load_only("email_address") ) .. note:: This method will still load a :class:`_schema.Column` even if the column property is defined with ``deferred=True`` for the :func:`.column_property` function. .. versionadded:: 0.9.0 """ cloned = loadopt.set_column_strategy( attrs, {"deferred": False, "instrument": True} ) cloned.set_column_strategy( "*", {"deferred": True, "instrument": True}, {"undefer_pks": True} ) return cloned @load_only._add_unbound_fn def load_only(*attrs): return _UnboundLoad().load_only(*attrs) @loader_option() def joinedload(loadopt, attr, innerjoin=None): """Indicate that the given attribute should be loaded using joined eager loading. This function is part of the :class:`_orm.Load` interface and supports both method-chained and standalone operation. examples:: # joined-load the "orders" collection on "User" query(User).options(joinedload(User.orders)) # joined-load Order.items and then Item.keywords query(Order).options( joinedload(Order.items).joinedload(Item.keywords)) # lazily load Order.items, but when Items are loaded, # joined-load the keywords collection query(Order).options( lazyload(Order.items).joinedload(Item.keywords)) :param innerjoin: if ``True``, indicates that the joined eager load should use an inner join instead of the default of left outer join:: query(Order).options(joinedload(Order.user, innerjoin=True)) In order to chain multiple eager joins together where some may be OUTER and others INNER, right-nested joins are used to link them:: query(A).options( joinedload(A.bs, innerjoin=False). joinedload(B.cs, innerjoin=True) ) The above query, linking A.bs via "outer" join and B.cs via "inner" join would render the joins as "a LEFT OUTER JOIN (b JOIN c)". When using older versions of SQLite (< 3.7.16), this form of JOIN is translated to use full subqueries as this syntax is otherwise not directly supported. The ``innerjoin`` flag can also be stated with the term ``"unnested"``. This indicates that an INNER JOIN should be used, *unless* the join is linked to a LEFT OUTER JOIN to the left, in which case it will render as LEFT OUTER JOIN. For example, supposing ``A.bs`` is an outerjoin:: query(A).options( joinedload(A.bs). joinedload(B.cs, innerjoin="unnested") ) The above join will render as "a LEFT OUTER JOIN b LEFT OUTER JOIN c", rather than as "a LEFT OUTER JOIN (b JOIN c)". .. note:: The "unnested" flag does **not** affect the JOIN rendered from a many-to-many association table, e.g. a table configured as :paramref:`_orm.relationship.secondary`, to the target table; for correctness of results, these joins are always INNER and are therefore right-nested if linked to an OUTER join. .. versionchanged:: 1.0.0 ``innerjoin=True`` now implies ``innerjoin="nested"``, whereas in 0.9 it implied ``innerjoin="unnested"``. In order to achieve the pre-1.0 "unnested" inner join behavior, use the value ``innerjoin="unnested"``. See :ref:`migration_3008`. .. note:: The joins produced by :func:`_orm.joinedload` are **anonymously aliased**. The criteria by which the join proceeds cannot be modified, nor can the :class:`_query.Query` refer to these joins in any way, including ordering. See :ref:`zen_of_eager_loading` for further detail. To produce a specific SQL JOIN which is explicitly available, use :meth:`_query.Query.join`. To combine explicit JOINs with eager loading of collections, use :func:`_orm.contains_eager`; see :ref:`contains_eager`. .. seealso:: :ref:`loading_toplevel` :ref:`joined_eager_loading` """ loader = loadopt.set_relationship_strategy(attr, {"lazy": "joined"}) if innerjoin is not None: loader.local_opts["innerjoin"] = innerjoin return loader @joinedload._add_unbound_fn def joinedload(*keys, **kw): return _UnboundLoad._from_keys(_UnboundLoad.joinedload, keys, False, kw) @joinedload._add_unbound_all_fn def joinedload_all(*keys, **kw): return _UnboundLoad._from_keys(_UnboundLoad.joinedload, keys, True, kw) @loader_option() def subqueryload(loadopt, attr): """Indicate that the given attribute should be loaded using subquery eager loading. This function is part of the :class:`_orm.Load` interface and supports both method-chained and standalone operation. examples:: # subquery-load the "orders" collection on "User" query(User).options(subqueryload(User.orders)) # subquery-load Order.items and then Item.keywords query(Order).options( subqueryload(Order.items).subqueryload(Item.keywords)) # lazily load Order.items, but when Items are loaded, # subquery-load the keywords collection query(Order).options( lazyload(Order.items).subqueryload(Item.keywords)) .. seealso:: :ref:`loading_toplevel` :ref:`subquery_eager_loading` """ return loadopt.set_relationship_strategy(attr, {"lazy": "subquery"}) @subqueryload._add_unbound_fn def subqueryload(*keys): return _UnboundLoad._from_keys(_UnboundLoad.subqueryload, keys, False, {}) @subqueryload._add_unbound_all_fn def subqueryload_all(*keys): return _UnboundLoad._from_keys(_UnboundLoad.subqueryload, keys, True, {}) @loader_option() def selectinload(loadopt, attr): """Indicate that the given attribute should be loaded using SELECT IN eager loading. This function is part of the :class:`_orm.Load` interface and supports both method-chained and standalone operation. examples:: # selectin-load the "orders" collection on "User" query(User).options(selectinload(User.orders)) # selectin-load Order.items and then Item.keywords query(Order).options( selectinload(Order.items).selectinload(Item.keywords)) # lazily load Order.items, but when Items are loaded, # selectin-load the keywords collection query(Order).options( lazyload(Order.items).selectinload(Item.keywords)) .. versionadded:: 1.2 .. seealso:: :ref:`loading_toplevel` :ref:`selectin_eager_loading` """ return loadopt.set_relationship_strategy(attr, {"lazy": "selectin"}) @selectinload._add_unbound_fn def selectinload(*keys): return _UnboundLoad._from_keys(_UnboundLoad.selectinload, keys, False, {}) @selectinload._add_unbound_all_fn def selectinload_all(*keys): return _UnboundLoad._from_keys(_UnboundLoad.selectinload, keys, True, {}) @loader_option() def lazyload(loadopt, attr): """Indicate that the given attribute should be loaded using "lazy" loading. This function is part of the :class:`_orm.Load` interface and supports both method-chained and standalone operation. .. seealso:: :ref:`loading_toplevel` :ref:`lazy_loading` """ return loadopt.set_relationship_strategy(attr, {"lazy": "select"}) @lazyload._add_unbound_fn def lazyload(*keys): return _UnboundLoad._from_keys(_UnboundLoad.lazyload, keys, False, {}) @lazyload._add_unbound_all_fn def lazyload_all(*keys): return _UnboundLoad._from_keys(_UnboundLoad.lazyload, keys, True, {}) @loader_option() def immediateload(loadopt, attr): """Indicate that the given attribute should be loaded using an immediate load with a per-attribute SELECT statement. The :func:`.immediateload` option is superseded in general by the :func:`.selectinload` option, which performs the same task more efficiently by emitting a SELECT for all loaded objects. This function is part of the :class:`_orm.Load` interface and supports both method-chained and standalone operation. .. seealso:: :ref:`loading_toplevel` :ref:`selectin_eager_loading` """ loader = loadopt.set_relationship_strategy(attr, {"lazy": "immediate"}) return loader @immediateload._add_unbound_fn def immediateload(*keys): return _UnboundLoad._from_keys(_UnboundLoad.immediateload, keys, False, {}) @loader_option() def noload(loadopt, attr): """Indicate that the given relationship attribute should remain unloaded. This function is part of the :class:`_orm.Load` interface and supports both method-chained and standalone operation. :func:`_orm.noload` applies to :func:`_orm.relationship` attributes; for column-based attributes, see :func:`_orm.defer`. .. seealso:: :ref:`loading_toplevel` """ return loadopt.set_relationship_strategy(attr, {"lazy": "noload"}) @noload._add_unbound_fn def noload(*keys): return _UnboundLoad._from_keys(_UnboundLoad.noload, keys, False, {}) @loader_option() def raiseload(loadopt, attr, sql_only=False): """Indicate that the given relationship attribute should disallow lazy loads. A relationship attribute configured with :func:`_orm.raiseload` will raise an :exc:`~sqlalchemy.exc.InvalidRequestError` upon access. The typical way this is useful is when an application is attempting to ensure that all relationship attributes that are accessed in a particular context would have been already loaded via eager loading. Instead of having to read through SQL logs to ensure lazy loads aren't occurring, this strategy will cause them to raise immediately. :param sql_only: if True, raise only if the lazy load would emit SQL, but not if it is only checking the identity map, or determining that the related value should just be None due to missing keys. When False, the strategy will raise for all varieties of lazyload. This function is part of the :class:`_orm.Load` interface and supports both method-chained and standalone operation. :func:`_orm.raiseload` applies to :func:`_orm.relationship` attributes only. .. versionadded:: 1.1 .. seealso:: :ref:`loading_toplevel` :ref:`prevent_lazy_with_raiseload` """ return loadopt.set_relationship_strategy( attr, {"lazy": "raise_on_sql" if sql_only else "raise"} ) @raiseload._add_unbound_fn def raiseload(*keys, **kw): return _UnboundLoad._from_keys(_UnboundLoad.raiseload, keys, False, kw) @loader_option() def defaultload(loadopt, attr): """Indicate an attribute should load using its default loader style. This method is used to link to other loader options further into a chain of attributes without altering the loader style of the links along the chain. For example, to set joined eager loading for an element of an element:: session.query(MyClass).options( defaultload(MyClass.someattribute). joinedload(MyOtherClass.someotherattribute) ) :func:`.defaultload` is also useful for setting column-level options on a related class, namely that of :func:`.defer` and :func:`.undefer`:: session.query(MyClass).options( defaultload(MyClass.someattribute). defer("some_column"). undefer("some_other_column") ) .. seealso:: :meth:`_orm.Load.options` - allows for complex hierarchical loader option structures with less verbosity than with individual :func:`.defaultload` directives. :ref:`relationship_loader_options` :ref:`deferred_loading_w_multiple` """ return loadopt.set_relationship_strategy(attr, None) @defaultload._add_unbound_fn def defaultload(*keys): return _UnboundLoad._from_keys(_UnboundLoad.defaultload, keys, False, {}) @loader_option() def defer(loadopt, key): r"""Indicate that the given column-oriented attribute should be deferred, e.g. not loaded until accessed. This function is part of the :class:`_orm.Load` interface and supports both method-chained and standalone operation. e.g.:: from sqlalchemy.orm import defer session.query(MyClass).options( defer("attribute_one"), defer("attribute_two")) session.query(MyClass).options( defer(MyClass.attribute_one), defer(MyClass.attribute_two)) To specify a deferred load of an attribute on a related class, the path can be specified one token at a time, specifying the loading style for each link along the chain. To leave the loading style for a link unchanged, use :func:`_orm.defaultload`:: session.query(MyClass).options(defaultload("someattr").defer("some_column")) A :class:`_orm.Load` object that is present on a certain path can have :meth:`_orm.Load.defer` called multiple times, each will operate on the same parent entity:: session.query(MyClass).options( defaultload("someattr"). defer("some_column"). defer("some_other_column"). defer("another_column") ) :param key: Attribute to be deferred. :param \*addl_attrs: This option supports the old 0.8 style of specifying a path as a series of attributes, which is now superseded by the method-chained style. .. deprecated:: 0.9 The \*addl_attrs on :func:`_orm.defer` is deprecated and will be removed in a future release. Please use method chaining in conjunction with defaultload() to indicate a path. .. seealso:: :ref:`deferred` :func:`_orm.undefer` """ return loadopt.set_column_strategy( (key,), {"deferred": True, "instrument": True} ) @defer._add_unbound_fn def defer(key, *addl_attrs): if addl_attrs: util.warn_deprecated( "The *addl_attrs on orm.defer is deprecated. Please use " "method chaining in conjunction with defaultload() to " "indicate a path." ) return _UnboundLoad._from_keys( _UnboundLoad.defer, (key,) + addl_attrs, False, {} ) @loader_option() def undefer(loadopt, key): r"""Indicate that the given column-oriented attribute should be undeferred, e.g. specified within the SELECT statement of the entity as a whole. The column being undeferred is typically set up on the mapping as a :func:`.deferred` attribute. This function is part of the :class:`_orm.Load` interface and supports both method-chained and standalone operation. Examples:: # undefer two columns session.query(MyClass).options(undefer("col1"), undefer("col2")) # undefer all columns specific to a single class using Load + * session.query(MyClass, MyOtherClass).options( Load(MyClass).undefer("*")) # undefer a column on a related object session.query(MyClass).options( defaultload(MyClass.items).undefer('text')) :param key: Attribute to be undeferred. :param \*addl_attrs: This option supports the old 0.8 style of specifying a path as a series of attributes, which is now superseded by the method-chained style. .. deprecated:: 0.9 The \*addl_attrs on :func:`_orm.undefer` is deprecated and will be removed in a future release. Please use method chaining in conjunction with defaultload() to indicate a path. .. seealso:: :ref:`deferred` :func:`_orm.defer` :func:`_orm.undefer_group` """ return loadopt.set_column_strategy( (key,), {"deferred": False, "instrument": True} ) @undefer._add_unbound_fn def undefer(key, *addl_attrs): if addl_attrs: util.warn_deprecated( "The *addl_attrs on orm.undefer is deprecated. Please use " "method chaining in conjunction with defaultload() to " "indicate a path." ) return _UnboundLoad._from_keys( _UnboundLoad.undefer, (key,) + addl_attrs, False, {} ) @loader_option() def undefer_group(loadopt, name): """Indicate that columns within the given deferred group name should be undeferred. The columns being undeferred are set up on the mapping as :func:`.deferred` attributes and include a "group" name. E.g:: session.query(MyClass).options(undefer_group("large_attrs")) To undefer a group of attributes on a related entity, the path can be spelled out using relationship loader options, such as :func:`_orm.defaultload`:: session.query(MyClass).options( defaultload("someattr").undefer_group("large_attrs")) .. versionchanged:: 0.9.0 :func:`_orm.undefer_group` is now specific to a particular entity load path. .. seealso:: :ref:`deferred` :func:`_orm.defer` :func:`_orm.undefer` """ return loadopt.set_column_strategy( "*", None, {"undefer_group_%s" % name: True}, opts_only=True ) @undefer_group._add_unbound_fn def undefer_group(name): return _UnboundLoad().undefer_group(name) @loader_option() def with_expression(loadopt, key, expression): r"""Apply an ad-hoc SQL expression to a "deferred expression" attribute. This option is used in conjunction with the :func:`_orm.query_expression` mapper-level construct that indicates an attribute which should be the target of an ad-hoc SQL expression. E.g.:: sess.query(SomeClass).options( with_expression(SomeClass.x_y_expr, SomeClass.x + SomeClass.y) ) .. versionadded:: 1.2 :param key: Attribute to be undeferred. :param expr: SQL expression to be applied to the attribute. .. note:: the target attribute is populated only if the target object is **not currently loaded** in the current :class:`_orm.Session` unless the :meth:`_query.Query.populate_existing` method is used. Please refer to :ref:`mapper_querytime_expression` for complete usage details. .. seealso:: :ref:`mapper_querytime_expression` """ expression = sql_expr._labeled(_orm_full_deannotate(expression)) return loadopt.set_column_strategy( (key,), {"query_expression": True}, opts={"expression": expression} ) @with_expression._add_unbound_fn def with_expression(key, expression): return _UnboundLoad._from_keys( _UnboundLoad.with_expression, (key,), False, {"expression": expression} ) @loader_option() def selectin_polymorphic(loadopt, classes): """Indicate an eager load should take place for all attributes specific to a subclass. This uses an additional SELECT with IN against all matched primary key values, and is the per-query analogue to the ``"selectin"`` setting on the :paramref:`.mapper.polymorphic_load` parameter. .. versionadded:: 1.2 .. seealso:: :ref:`polymorphic_selectin` """ loadopt.set_class_strategy( {"selectinload_polymorphic": True}, opts={ "entities": tuple( sorted((inspect(cls) for cls in classes), key=id) ) }, ) return loadopt @selectin_polymorphic._add_unbound_fn def selectin_polymorphic(base_cls, classes): ul = _UnboundLoad() ul.is_class_strategy = True ul.path = (inspect(base_cls),) ul.selectin_polymorphic(classes) return ul