Mini Shell
# 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
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