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bazarr/libs/sqlalchemy/orm/base.py

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# orm/base.py
# Copyright (C) 2005-2023 the SQLAlchemy authors and contributors
# <see AUTHORS file>
#
# This module is part of SQLAlchemy and is released under
# the MIT License: https://www.opensource.org/licenses/mit-license.php
"""Constants and rudimental functions used throughout the ORM.
"""
from __future__ import annotations
from enum import Enum
import operator
import typing
from typing import Any
from typing import Callable
from typing import Dict
from typing import Generic
from typing import no_type_check
from typing import Optional
from typing import overload
from typing import Type
from typing import TYPE_CHECKING
from typing import TypeVar
from typing import Union
from . import exc
from ._typing import insp_is_mapper
from .. import exc as sa_exc
from .. import inspection
from .. import util
from ..sql import roles
from ..sql.elements import SQLColumnExpression
from ..sql.elements import SQLCoreOperations
from ..util import FastIntFlag
from ..util.langhelpers import TypingOnly
from ..util.typing import Literal
if typing.TYPE_CHECKING:
from ._typing import _EntityType
from ._typing import _ExternalEntityType
from ._typing import _InternalEntityType
from .attributes import InstrumentedAttribute
from .dynamic import AppenderQuery
from .instrumentation import ClassManager
from .interfaces import PropComparator
from .mapper import Mapper
from .state import InstanceState
from .util import AliasedClass
from .writeonly import WriteOnlyCollection
from ..sql._typing import _ColumnExpressionArgument
from ..sql._typing import _InfoType
from ..sql.elements import ColumnElement
from ..sql.operators import OperatorType
_T = TypeVar("_T", bound=Any)
_O = TypeVar("_O", bound=object)
class LoaderCallableStatus(Enum):
PASSIVE_NO_RESULT = 0
"""Symbol returned by a loader callable or other attribute/history
retrieval operation when a value could not be determined, based
on loader callable flags.
"""
PASSIVE_CLASS_MISMATCH = 1
"""Symbol indicating that an object is locally present for a given
primary key identity but it is not of the requested class. The
return value is therefore None and no SQL should be emitted."""
ATTR_WAS_SET = 2
"""Symbol returned by a loader callable to indicate the
retrieved value, or values, were assigned to their attributes
on the target object.
"""
ATTR_EMPTY = 3
"""Symbol used internally to indicate an attribute had no callable."""
NO_VALUE = 4
"""Symbol which may be placed as the 'previous' value of an attribute,
indicating no value was loaded for an attribute when it was modified,
and flags indicated we were not to load it.
"""
NEVER_SET = NO_VALUE
"""
Synonymous with NO_VALUE
.. versionchanged:: 1.4 NEVER_SET was merged with NO_VALUE
"""
(
PASSIVE_NO_RESULT,
PASSIVE_CLASS_MISMATCH,
ATTR_WAS_SET,
ATTR_EMPTY,
NO_VALUE,
) = tuple(LoaderCallableStatus)
NEVER_SET = NO_VALUE
class PassiveFlag(FastIntFlag):
"""Bitflag interface that passes options onto loader callables"""
NO_CHANGE = 0
"""No callables or SQL should be emitted on attribute access
and no state should change
"""
CALLABLES_OK = 1
"""Loader callables can be fired off if a value
is not present.
"""
SQL_OK = 2
"""Loader callables can emit SQL at least on scalar value attributes."""
RELATED_OBJECT_OK = 4
"""Callables can use SQL to load related objects as well
as scalar value attributes.
"""
INIT_OK = 8
"""Attributes should be initialized with a blank
value (None or an empty collection) upon get, if no other
value can be obtained.
"""
NON_PERSISTENT_OK = 16
"""Callables can be emitted if the parent is not persistent."""
LOAD_AGAINST_COMMITTED = 32
"""Callables should use committed values as primary/foreign keys during a
load.
"""
NO_AUTOFLUSH = 64
"""Loader callables should disable autoflush.""",
NO_RAISE = 128
"""Loader callables should not raise any assertions"""
DEFERRED_HISTORY_LOAD = 256
"""indicates special load of the previous value of an attribute"""
# pre-packaged sets of flags used as inputs
PASSIVE_OFF = (
RELATED_OBJECT_OK | NON_PERSISTENT_OK | INIT_OK | CALLABLES_OK | SQL_OK
)
"Callables can be emitted in all cases."
PASSIVE_RETURN_NO_VALUE = PASSIVE_OFF ^ INIT_OK
"""PASSIVE_OFF ^ INIT_OK"""
PASSIVE_NO_INITIALIZE = PASSIVE_RETURN_NO_VALUE ^ CALLABLES_OK
"PASSIVE_RETURN_NO_VALUE ^ CALLABLES_OK"
PASSIVE_NO_FETCH = PASSIVE_OFF ^ SQL_OK
"PASSIVE_OFF ^ SQL_OK"
PASSIVE_NO_FETCH_RELATED = PASSIVE_OFF ^ RELATED_OBJECT_OK
"PASSIVE_OFF ^ RELATED_OBJECT_OK"
PASSIVE_ONLY_PERSISTENT = PASSIVE_OFF ^ NON_PERSISTENT_OK
"PASSIVE_OFF ^ NON_PERSISTENT_OK"
PASSIVE_MERGE = PASSIVE_OFF | NO_RAISE
"""PASSIVE_OFF | NO_RAISE
Symbol used specifically for session.merge() and similar cases
"""
(
NO_CHANGE,
CALLABLES_OK,
SQL_OK,
RELATED_OBJECT_OK,
INIT_OK,
NON_PERSISTENT_OK,
LOAD_AGAINST_COMMITTED,
NO_AUTOFLUSH,
NO_RAISE,
DEFERRED_HISTORY_LOAD,
PASSIVE_OFF,
PASSIVE_RETURN_NO_VALUE,
PASSIVE_NO_INITIALIZE,
PASSIVE_NO_FETCH,
PASSIVE_NO_FETCH_RELATED,
PASSIVE_ONLY_PERSISTENT,
PASSIVE_MERGE,
) = PassiveFlag.__members__.values()
DEFAULT_MANAGER_ATTR = "_sa_class_manager"
DEFAULT_STATE_ATTR = "_sa_instance_state"
class EventConstants(Enum):
EXT_CONTINUE = 1
EXT_STOP = 2
EXT_SKIP = 3
NO_KEY = 4
"""indicates an :class:`.AttributeEvent` event that did not have any
key argument.
.. versionadded:: 2.0
"""
EXT_CONTINUE, EXT_STOP, EXT_SKIP, NO_KEY = tuple(EventConstants)
class RelationshipDirection(Enum):
"""enumeration which indicates the 'direction' of a
:class:`_orm.RelationshipProperty`.
:class:`.RelationshipDirection` is accessible from the
:attr:`_orm.Relationship.direction` attribute of
:class:`_orm.RelationshipProperty`.
"""
ONETOMANY = 1
"""Indicates the one-to-many direction for a :func:`_orm.relationship`.
This symbol is typically used by the internals but may be exposed within
certain API features.
"""
MANYTOONE = 2
"""Indicates the many-to-one direction for a :func:`_orm.relationship`.
This symbol is typically used by the internals but may be exposed within
certain API features.
"""
MANYTOMANY = 3
"""Indicates the many-to-many direction for a :func:`_orm.relationship`.
This symbol is typically used by the internals but may be exposed within
certain API features.
"""
ONETOMANY, MANYTOONE, MANYTOMANY = tuple(RelationshipDirection)
class InspectionAttrExtensionType(Enum):
"""Symbols indicating the type of extension that a
:class:`.InspectionAttr` is part of."""
class NotExtension(InspectionAttrExtensionType):
NOT_EXTENSION = "not_extension"
"""Symbol indicating an :class:`InspectionAttr` that's
not part of sqlalchemy.ext.
Is assigned to the :attr:`.InspectionAttr.extension_type`
attribute.
"""
_never_set = frozenset([NEVER_SET])
_none_set = frozenset([None, NEVER_SET, PASSIVE_NO_RESULT])
_SET_DEFERRED_EXPIRED = util.symbol("SET_DEFERRED_EXPIRED")
_DEFER_FOR_STATE = util.symbol("DEFER_FOR_STATE")
_RAISE_FOR_STATE = util.symbol("RAISE_FOR_STATE")
_F = TypeVar("_F", bound=Callable[..., Any])
_Self = TypeVar("_Self")
def _assertions(
*assertions: Any,
) -> Callable[[_F], _F]:
@util.decorator
def generate(fn: _F, self: _Self, *args: Any, **kw: Any) -> _Self:
for assertion in assertions:
assertion(self, fn.__name__)
fn(self, *args, **kw)
return self
return generate
if TYPE_CHECKING:
def manager_of_class(cls: Type[_O]) -> ClassManager[_O]:
...
@overload
def opt_manager_of_class(cls: AliasedClass[Any]) -> None:
...
@overload
def opt_manager_of_class(
cls: _ExternalEntityType[_O],
) -> Optional[ClassManager[_O]]:
...
def opt_manager_of_class(
cls: _ExternalEntityType[_O],
) -> Optional[ClassManager[_O]]:
...
def instance_state(instance: _O) -> InstanceState[_O]:
...
def instance_dict(instance: object) -> Dict[str, Any]:
...
else:
# these can be replaced by sqlalchemy.ext.instrumentation
# if augmented class instrumentation is enabled.
def manager_of_class(cls):
try:
return cls.__dict__[DEFAULT_MANAGER_ATTR]
except KeyError as ke:
raise exc.UnmappedClassError(
cls, f"Can't locate an instrumentation manager for class {cls}"
) from ke
def opt_manager_of_class(cls):
return cls.__dict__.get(DEFAULT_MANAGER_ATTR)
instance_state = operator.attrgetter(DEFAULT_STATE_ATTR)
instance_dict = operator.attrgetter("__dict__")
def instance_str(instance: object) -> str:
"""Return a string describing an instance."""
return state_str(instance_state(instance))
def state_str(state: InstanceState[Any]) -> str:
"""Return a string describing an instance via its InstanceState."""
if state is None:
return "None"
else:
return "<%s at 0x%x>" % (state.class_.__name__, id(state.obj()))
def state_class_str(state: InstanceState[Any]) -> str:
"""Return a string describing an instance's class via its
InstanceState.
"""
if state is None:
return "None"
else:
return "<%s>" % (state.class_.__name__,)
def attribute_str(instance: object, attribute: str) -> str:
return instance_str(instance) + "." + attribute
def state_attribute_str(state: InstanceState[Any], attribute: str) -> str:
return state_str(state) + "." + attribute
def object_mapper(instance: _T) -> Mapper[_T]:
"""Given an object, return the primary Mapper associated with the object
instance.
Raises :class:`sqlalchemy.orm.exc.UnmappedInstanceError`
if no mapping is configured.
This function is available via the inspection system as::
inspect(instance).mapper
Using the inspection system will raise
:class:`sqlalchemy.exc.NoInspectionAvailable` if the instance is
not part of a mapping.
"""
return object_state(instance).mapper
def object_state(instance: _T) -> InstanceState[_T]:
"""Given an object, return the :class:`.InstanceState`
associated with the object.
Raises :class:`sqlalchemy.orm.exc.UnmappedInstanceError`
if no mapping is configured.
Equivalent functionality is available via the :func:`_sa.inspect`
function as::
inspect(instance)
Using the inspection system will raise
:class:`sqlalchemy.exc.NoInspectionAvailable` if the instance is
not part of a mapping.
"""
state = _inspect_mapped_object(instance)
if state is None:
raise exc.UnmappedInstanceError(instance)
else:
return state
@inspection._inspects(object)
def _inspect_mapped_object(instance: _T) -> Optional[InstanceState[_T]]:
try:
return instance_state(instance)
except (exc.UnmappedClassError,) + exc.NO_STATE:
return None
def _class_to_mapper(
class_or_mapper: Union[Mapper[_T], Type[_T]]
) -> Mapper[_T]:
# can't get mypy to see an overload for this
insp = inspection.inspect(class_or_mapper, False)
if insp is not None:
return insp.mapper # type: ignore
else:
assert isinstance(class_or_mapper, type)
raise exc.UnmappedClassError(class_or_mapper)
def _mapper_or_none(
entity: Union[Type[_T], _InternalEntityType[_T]]
) -> Optional[Mapper[_T]]:
"""Return the :class:`_orm.Mapper` for the given class or None if the
class is not mapped.
"""
# can't get mypy to see an overload for this
insp = inspection.inspect(entity, False)
if insp is not None:
return insp.mapper # type: ignore
else:
return None
def _is_mapped_class(entity: Any) -> bool:
"""Return True if the given object is a mapped class,
:class:`_orm.Mapper`, or :class:`.AliasedClass`.
"""
insp = inspection.inspect(entity, False)
return (
insp is not None
and not insp.is_clause_element
and (insp.is_mapper or insp.is_aliased_class)
)
def _is_aliased_class(entity: Any) -> bool:
insp = inspection.inspect(entity, False)
return insp is not None and getattr(insp, "is_aliased_class", False)
@no_type_check
def _entity_descriptor(entity: _EntityType[Any], key: str) -> Any:
"""Return a class attribute given an entity and string name.
May return :class:`.InstrumentedAttribute` or user-defined
attribute.
"""
insp = inspection.inspect(entity)
if insp.is_selectable:
description = entity
entity = insp.c
elif insp.is_aliased_class:
entity = insp.entity
description = entity
elif hasattr(insp, "mapper"):
description = entity = insp.mapper.class_
else:
description = entity
try:
return getattr(entity, key)
except AttributeError as err:
raise sa_exc.InvalidRequestError(
"Entity '%s' has no property '%s'" % (description, key)
) from err
if TYPE_CHECKING:
def _state_mapper(state: InstanceState[_O]) -> Mapper[_O]:
...
else:
_state_mapper = util.dottedgetter("manager.mapper")
def _inspect_mapped_class(
class_: Type[_O], configure: bool = False
) -> Optional[Mapper[_O]]:
try:
class_manager = opt_manager_of_class(class_)
if class_manager is None or not class_manager.is_mapped:
return None
mapper = class_manager.mapper
except exc.NO_STATE:
return None
else:
if configure:
mapper._check_configure()
return mapper
def _parse_mapper_argument(arg: Union[Mapper[_O], Type[_O]]) -> Mapper[_O]:
insp = inspection.inspect(arg, raiseerr=False)
if insp_is_mapper(insp):
return insp
raise sa_exc.ArgumentError(f"Mapper or mapped class expected, got {arg!r}")
def class_mapper(class_: Type[_O], configure: bool = True) -> Mapper[_O]:
"""Given a class, return the primary :class:`_orm.Mapper` associated
with the key.
Raises :exc:`.UnmappedClassError` if no mapping is configured
on the given class, or :exc:`.ArgumentError` if a non-class
object is passed.
Equivalent functionality is available via the :func:`_sa.inspect`
function as::
inspect(some_mapped_class)
Using the inspection system will raise
:class:`sqlalchemy.exc.NoInspectionAvailable` if the class is not mapped.
"""
mapper = _inspect_mapped_class(class_, configure=configure)
if mapper is None:
if not isinstance(class_, type):
raise sa_exc.ArgumentError(
"Class object expected, got '%r'." % (class_,)
)
raise exc.UnmappedClassError(class_)
else:
return mapper
class InspectionAttr:
"""A base class applied to all ORM objects and attributes that are
related to things that can be returned by the :func:`_sa.inspect` function.
The attributes defined here allow the usage of simple boolean
checks to test basic facts about the object returned.
While the boolean checks here are basically the same as using
the Python isinstance() function, the flags here can be used without
the need to import all of these classes, and also such that
the SQLAlchemy class system can change while leaving the flags
here intact for forwards-compatibility.
"""
__slots__ = ()
is_selectable = False
"""Return True if this object is an instance of
:class:`_expression.Selectable`."""
is_aliased_class = False
"""True if this object is an instance of :class:`.AliasedClass`."""
is_instance = False
"""True if this object is an instance of :class:`.InstanceState`."""
is_mapper = False
"""True if this object is an instance of :class:`_orm.Mapper`."""
is_bundle = False
"""True if this object is an instance of :class:`.Bundle`."""
is_property = False
"""True if this object is an instance of :class:`.MapperProperty`."""
is_attribute = False
"""True if this object is a Python :term:`descriptor`.
This can refer to one of many types. Usually a
:class:`.QueryableAttribute` which handles attributes events on behalf
of a :class:`.MapperProperty`. But can also be an extension type
such as :class:`.AssociationProxy` or :class:`.hybrid_property`.
The :attr:`.InspectionAttr.extension_type` will refer to a constant
identifying the specific subtype.
.. seealso::
:attr:`_orm.Mapper.all_orm_descriptors`
"""
_is_internal_proxy = False
"""True if this object is an internal proxy object.
.. versionadded:: 1.2.12
"""
is_clause_element = False
"""True if this object is an instance of
:class:`_expression.ClauseElement`."""
extension_type: InspectionAttrExtensionType = NotExtension.NOT_EXTENSION
"""The extension type, if any.
Defaults to :attr:`.interfaces.NotExtension.NOT_EXTENSION`
.. seealso::
:class:`.HybridExtensionType`
:class:`.AssociationProxyExtensionType`
"""
class InspectionAttrInfo(InspectionAttr):
"""Adds the ``.info`` attribute to :class:`.InspectionAttr`.
The rationale for :class:`.InspectionAttr` vs. :class:`.InspectionAttrInfo`
is that the former is compatible as a mixin for classes that specify
``__slots__``; this is essentially an implementation artifact.
"""
__slots__ = ()
@util.ro_memoized_property
def info(self) -> _InfoType:
"""Info dictionary associated with the object, allowing user-defined
data to be associated with this :class:`.InspectionAttr`.
The dictionary is generated when first accessed. Alternatively,
it can be specified as a constructor argument to the
:func:`.column_property`, :func:`_orm.relationship`, or
:func:`.composite`
functions.
.. versionchanged:: 1.0.0 :attr:`.MapperProperty.info` is also
available on extension types via the
:attr:`.InspectionAttrInfo.info` attribute, so that it can apply
to a wider variety of ORM and extension constructs.
.. seealso::
:attr:`.QueryableAttribute.info`
:attr:`.SchemaItem.info`
"""
return {}
class SQLORMOperations(SQLCoreOperations[_T], TypingOnly):
__slots__ = ()
if typing.TYPE_CHECKING:
def of_type(self, class_: _EntityType[Any]) -> PropComparator[_T]:
...
def and_(
self, *criteria: _ColumnExpressionArgument[bool]
) -> PropComparator[bool]:
...
def any( # noqa: A001
self,
criterion: Optional[_ColumnExpressionArgument[bool]] = None,
**kwargs: Any,
) -> ColumnElement[bool]:
...
def has(
self,
criterion: Optional[_ColumnExpressionArgument[bool]] = None,
**kwargs: Any,
) -> ColumnElement[bool]:
...
class ORMDescriptor(Generic[_T], TypingOnly):
"""Represent any Python descriptor that provides a SQL expression
construct at the class level."""
__slots__ = ()
if typing.TYPE_CHECKING:
@overload
def __get__(
self, instance: Any, owner: Literal[None]
) -> ORMDescriptor[_T]:
...
@overload
def __get__(
self, instance: Literal[None], owner: Any
) -> SQLCoreOperations[_T]:
...
@overload
def __get__(self, instance: object, owner: Any) -> _T:
...
def __get__(
self, instance: object, owner: Any
) -> Union[ORMDescriptor[_T], SQLCoreOperations[_T], _T]:
...
class _MappedAnnotationBase(Generic[_T], TypingOnly):
"""common class for Mapped and similar ORM container classes.
these are classes that can appear on the left side of an ORM declarative
mapping, containing a mapped class or in some cases a collection
surrounding a mapped class.
"""
__slots__ = ()
class SQLORMExpression(
SQLORMOperations[_T], SQLColumnExpression[_T], TypingOnly
):
"""A type that may be used to indicate any ORM-level attribute or
object that acts in place of one, in the context of SQL expression
construction.
:class:`.SQLORMExpression` extends from the Core
:class:`.SQLColumnExpression` to add additional SQL methods that are ORM
specific, such as :meth:`.PropComparator.of_type`, and is part of the bases
for :class:`.InstrumentedAttribute`. It may be used in :pep:`484` typing to
indicate arguments or return values that should behave as ORM-level
attribute expressions.
.. versionadded:: 2.0.0b4
"""
__slots__ = ()
class Mapped(
SQLORMExpression[_T],
ORMDescriptor[_T],
_MappedAnnotationBase[_T],
roles.DDLConstraintColumnRole,
):
"""Represent an ORM mapped attribute on a mapped class.
This class represents the complete descriptor interface for any class
attribute that will have been :term:`instrumented` by the ORM
:class:`_orm.Mapper` class. Provides appropriate information to type
checkers such as pylance and mypy so that ORM-mapped attributes
are correctly typed.
The most prominent use of :class:`_orm.Mapped` is in
the :ref:`Declarative Mapping <orm_explicit_declarative_base>` form
of :class:`_orm.Mapper` configuration, where used explicitly it drives
the configuration of ORM attributes such as :func:`_orm.mapped_class`
and :func:`_orm.relationship`.
.. seealso::
:ref:`orm_explicit_declarative_base`
:ref:`orm_declarative_table`
.. tip::
The :class:`_orm.Mapped` class represents attributes that are handled
directly by the :class:`_orm.Mapper` class. It does not include other
Python descriptor classes that are provided as extensions, including
:ref:`hybrids_toplevel` and the :ref:`associationproxy_toplevel`.
While these systems still make use of ORM-specific superclasses
and structures, they are not :term:`instrumented` by the
:class:`_orm.Mapper` and instead provide their own functionality
when they are accessed on a class.
.. versionadded:: 1.4
"""
__slots__ = ()
if typing.TYPE_CHECKING:
@overload
def __get__(
self, instance: None, owner: Any
) -> InstrumentedAttribute[_T]:
...
@overload
def __get__(self, instance: object, owner: Any) -> _T:
...
def __get__(
self, instance: Optional[object], owner: Any
) -> Union[InstrumentedAttribute[_T], _T]:
...
@classmethod
def _empty_constructor(cls, arg1: Any) -> Mapped[_T]:
...
def __set__(
self, instance: Any, value: Union[SQLCoreOperations[_T], _T]
) -> None:
...
def __delete__(self, instance: Any) -> None:
...
class _MappedAttribute(Generic[_T], TypingOnly):
"""Mixin for attributes which should be replaced by mapper-assigned
attributes.
"""
__slots__ = ()
class _DeclarativeMapped(Mapped[_T], _MappedAttribute[_T]):
"""Mixin for :class:`.MapperProperty` subclasses that allows them to
be compatible with ORM-annotated declarative mappings.
"""
__slots__ = ()
# MappedSQLExpression, Relationship, Composite etc. dont actually do
# SQL expression behavior. yet there is code that compares them with
# __eq__(), __ne__(), etc. Since #8847 made Mapped even more full
# featured including ColumnOperators, we need to have those methods
# be no-ops for these objects, so return NotImplemented to fall back
# to normal comparison behavior.
def operate(self, op: OperatorType, *other: Any, **kwargs: Any) -> Any:
return NotImplemented
__sa_operate__ = operate
def reverse_operate(
self, op: OperatorType, other: Any, **kwargs: Any
) -> Any:
return NotImplemented
class DynamicMapped(_MappedAnnotationBase[_T]):
"""Represent the ORM mapped attribute type for a "dynamic" relationship.
The :class:`_orm.DynamicMapped` type annotation may be used in an
:ref:`Annotated Declarative Table <orm_declarative_mapped_column>` mapping
to indicate that the ``lazy="dynamic"`` loader strategy should be used
for a particular :func:`_orm.relationship`.
.. legacy:: The "dynamic" lazy loader strategy is the legacy form of what
is now the "write_only" strategy described in the section
:ref:`write_only_relationship`.
E.g.::
class User(Base):
__tablename__ = "user"
id: Mapped[int] = mapped_column(primary_key=True)
addresses: DynamicMapped[Address] = relationship(
cascade="all,delete-orphan"
)
See the section :ref:`dynamic_relationship` for background.
.. versionadded:: 2.0
.. seealso::
:ref:`dynamic_relationship` - complete background
:class:`.WriteOnlyMapped` - fully 2.0 style version
"""
__slots__ = ()
if TYPE_CHECKING:
def __get__(
self, instance: Optional[object], owner: Any
) -> AppenderQuery[_T]:
...
def __set__(self, instance: Any, value: typing.Collection[_T]) -> None:
...
class WriteOnlyMapped(_MappedAnnotationBase[_T]):
"""Represent the ORM mapped attribute type for a "write only" relationship.
The :class:`_orm.WriteOnlyMapped` type annotation may be used in an
:ref:`Annotated Declarative Table <orm_declarative_mapped_column>` mapping
to indicate that the ``lazy="write_only"`` loader strategy should be used
for a particular :func:`_orm.relationship`.
E.g.::
class User(Base):
__tablename__ = "user"
id: Mapped[int] = mapped_column(primary_key=True)
addresses: WriteOnlyMapped[Address] = relationship(
cascade="all,delete-orphan"
)
See the section :ref:`write_only_relationship` for background.
.. versionadded:: 2.0
.. seealso::
:ref:`write_only_relationship` - complete background
:class:`.DynamicMapped` - includes legacy :class:`_orm.Query` support
"""
__slots__ = ()
if TYPE_CHECKING:
def __get__(
self, instance: Optional[object], owner: Any
) -> WriteOnlyCollection[_T]:
...
def __set__(self, instance: Any, value: typing.Collection[_T]) -> None:
...
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