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+# orm/interfaces.py
+# Copyright (C) 2005-2024 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
+
+"""
+
+Contains various base classes used throughout the ORM.
+
+Defines some key base classes prominent within the internals.
+
+This module and the classes within are mostly private, though some attributes
+are exposed when inspecting mappings.
+
+"""
+
+from __future__ import annotations
+
+import collections
+import dataclasses
+import typing
+from typing import Any
+from typing import Callable
+from typing import cast
+from typing import ClassVar
+from typing import Dict
+from typing import Generic
+from typing import Iterator
+from typing import List
+from typing import NamedTuple
+from typing import NoReturn
+from typing import Optional
+from typing import Sequence
+from typing import Set
+from typing import Tuple
+from typing import Type
+from typing import TYPE_CHECKING
+from typing import TypeVar
+from typing import Union
+
+from . import exc as orm_exc
+from . import path_registry
+from .base import _MappedAttribute as _MappedAttribute
+from .base import EXT_CONTINUE as EXT_CONTINUE  # noqa: F401
+from .base import EXT_SKIP as EXT_SKIP  # noqa: F401
+from .base import EXT_STOP as EXT_STOP  # noqa: F401
+from .base import InspectionAttr as InspectionAttr  # noqa: F401
+from .base import InspectionAttrInfo as InspectionAttrInfo
+from .base import MANYTOMANY as MANYTOMANY  # noqa: F401
+from .base import MANYTOONE as MANYTOONE  # noqa: F401
+from .base import NO_KEY as NO_KEY  # noqa: F401
+from .base import NO_VALUE as NO_VALUE  # noqa: F401
+from .base import NotExtension as NotExtension  # noqa: F401
+from .base import ONETOMANY as ONETOMANY  # noqa: F401
+from .base import RelationshipDirection as RelationshipDirection  # noqa: F401
+from .base import SQLORMOperations
+from .. import ColumnElement
+from .. import exc as sa_exc
+from .. import inspection
+from .. import util
+from ..sql import operators
+from ..sql import roles
+from ..sql import visitors
+from ..sql.base import _NoArg
+from ..sql.base import ExecutableOption
+from ..sql.cache_key import HasCacheKey
+from ..sql.operators import ColumnOperators
+from ..sql.schema import Column
+from ..sql.type_api import TypeEngine
+from ..util import warn_deprecated
+from ..util.typing import RODescriptorReference
+from ..util.typing import TypedDict
+
+if typing.TYPE_CHECKING:
+    from ._typing import _EntityType
+    from ._typing import _IdentityKeyType
+    from ._typing import _InstanceDict
+    from ._typing import _InternalEntityType
+    from ._typing import _ORMAdapterProto
+    from .attributes import InstrumentedAttribute
+    from .base import Mapped
+    from .context import _MapperEntity
+    from .context import ORMCompileState
+    from .context import QueryContext
+    from .decl_api import RegistryType
+    from .decl_base import _ClassScanMapperConfig
+    from .loading import _PopulatorDict
+    from .mapper import Mapper
+    from .path_registry import AbstractEntityRegistry
+    from .query import Query
+    from .session import Session
+    from .state import InstanceState
+    from .strategy_options import _LoadElement
+    from .util import AliasedInsp
+    from .util import ORMAdapter
+    from ..engine.result import Result
+    from ..sql._typing import _ColumnExpressionArgument
+    from ..sql._typing import _ColumnsClauseArgument
+    from ..sql._typing import _DMLColumnArgument
+    from ..sql._typing import _InfoType
+    from ..sql.operators import OperatorType
+    from ..sql.visitors import _TraverseInternalsType
+    from ..util.typing import _AnnotationScanType
+
+_StrategyKey = Tuple[Any, ...]
+
+_T = TypeVar("_T", bound=Any)
+_T_co = TypeVar("_T_co", bound=Any, covariant=True)
+
+_TLS = TypeVar("_TLS", bound="Type[LoaderStrategy]")
+
+
+class ORMStatementRole(roles.StatementRole):
+    __slots__ = ()
+    _role_name = (
+        "Executable SQL or text() construct, including ORM aware objects"
+    )
+
+
+class ORMColumnsClauseRole(
+    roles.ColumnsClauseRole, roles.TypedColumnsClauseRole[_T]
+):
+    __slots__ = ()
+    _role_name = "ORM mapped entity, aliased entity, or Column expression"
+
+
+class ORMEntityColumnsClauseRole(ORMColumnsClauseRole[_T]):
+    __slots__ = ()
+    _role_name = "ORM mapped or aliased entity"
+
+
+class ORMFromClauseRole(roles.StrictFromClauseRole):
+    __slots__ = ()
+    _role_name = "ORM mapped entity, aliased entity, or FROM expression"
+
+
+class ORMColumnDescription(TypedDict):
+    name: str
+    # TODO: add python_type and sql_type here; combining them
+    # into "type" is a bad idea
+    type: Union[Type[Any], TypeEngine[Any]]
+    aliased: bool
+    expr: _ColumnsClauseArgument[Any]
+    entity: Optional[_ColumnsClauseArgument[Any]]
+
+
+class _IntrospectsAnnotations:
+    __slots__ = ()
+
+    @classmethod
+    def _mapper_property_name(cls) -> str:
+        return cls.__name__
+
+    def found_in_pep593_annotated(self) -> Any:
+        """return a copy of this object to use in declarative when the
+        object is found inside of an Annotated object."""
+
+        raise NotImplementedError(
+            f"Use of the {self._mapper_property_name()!r} "
+            "construct inside of an Annotated object is not yet supported."
+        )
+
+    def declarative_scan(
+        self,
+        decl_scan: _ClassScanMapperConfig,
+        registry: RegistryType,
+        cls: Type[Any],
+        originating_module: Optional[str],
+        key: str,
+        mapped_container: Optional[Type[Mapped[Any]]],
+        annotation: Optional[_AnnotationScanType],
+        extracted_mapped_annotation: Optional[_AnnotationScanType],
+        is_dataclass_field: bool,
+    ) -> None:
+        """Perform class-specific initializaton at early declarative scanning
+        time.
+
+        .. versionadded:: 2.0
+
+        """
+
+    def _raise_for_required(self, key: str, cls: Type[Any]) -> NoReturn:
+        raise sa_exc.ArgumentError(
+            f"Python typing annotation is required for attribute "
+            f'"{cls.__name__}.{key}" when primary argument(s) for '
+            f'"{self._mapper_property_name()}" '
+            "construct are None or not present"
+        )
+
+
+class _AttributeOptions(NamedTuple):
+    """define Python-local attribute behavior options common to all
+    :class:`.MapperProperty` objects.
+
+    Currently this includes dataclass-generation arguments.
+
+    .. versionadded:: 2.0
+
+    """
+
+    dataclasses_init: Union[_NoArg, bool]
+    dataclasses_repr: Union[_NoArg, bool]
+    dataclasses_default: Union[_NoArg, Any]
+    dataclasses_default_factory: Union[_NoArg, Callable[[], Any]]
+    dataclasses_compare: Union[_NoArg, bool]
+    dataclasses_kw_only: Union[_NoArg, bool]
+
+    def _as_dataclass_field(self, key: str) -> Any:
+        """Return a ``dataclasses.Field`` object given these arguments."""
+
+        kw: Dict[str, Any] = {}
+        if self.dataclasses_default_factory is not _NoArg.NO_ARG:
+            kw["default_factory"] = self.dataclasses_default_factory
+        if self.dataclasses_default is not _NoArg.NO_ARG:
+            kw["default"] = self.dataclasses_default
+        if self.dataclasses_init is not _NoArg.NO_ARG:
+            kw["init"] = self.dataclasses_init
+        if self.dataclasses_repr is not _NoArg.NO_ARG:
+            kw["repr"] = self.dataclasses_repr
+        if self.dataclasses_compare is not _NoArg.NO_ARG:
+            kw["compare"] = self.dataclasses_compare
+        if self.dataclasses_kw_only is not _NoArg.NO_ARG:
+            kw["kw_only"] = self.dataclasses_kw_only
+
+        if "default" in kw and callable(kw["default"]):
+            # callable defaults are ambiguous. deprecate them in favour of
+            # insert_default or default_factory. #9936
+            warn_deprecated(
+                f"Callable object passed to the ``default`` parameter for "
+                f"attribute {key!r} in a ORM-mapped Dataclasses context is "
+                "ambiguous, "
+                "and this use will raise an error in a future release.  "
+                "If this callable is intended to produce Core level INSERT "
+                "default values for an underlying ``Column``, use "
+                "the ``mapped_column.insert_default`` parameter instead.  "
+                "To establish this callable as providing a default value "
+                "for instances of the dataclass itself, use the "
+                "``default_factory`` dataclasses parameter.",
+                "2.0",
+            )
+
+        if (
+            "init" in kw
+            and not kw["init"]
+            and "default" in kw
+            and not callable(kw["default"])  # ignore callable defaults. #9936
+            and "default_factory" not in kw  # illegal but let dc.field raise
+        ):
+            # fix for #9879
+            default = kw.pop("default")
+            kw["default_factory"] = lambda: default
+
+        return dataclasses.field(**kw)
+
+    @classmethod
+    def _get_arguments_for_make_dataclass(
+        cls,
+        key: str,
+        annotation: _AnnotationScanType,
+        mapped_container: Optional[Any],
+        elem: _T,
+    ) -> Union[
+        Tuple[str, _AnnotationScanType],
+        Tuple[str, _AnnotationScanType, dataclasses.Field[Any]],
+    ]:
+        """given attribute key, annotation, and value from a class, return
+        the argument tuple we would pass to dataclasses.make_dataclass()
+        for this attribute.
+
+        """
+        if isinstance(elem, _DCAttributeOptions):
+            dc_field = elem._attribute_options._as_dataclass_field(key)
+
+            return (key, annotation, dc_field)
+        elif elem is not _NoArg.NO_ARG:
+            # why is typing not erroring on this?
+            return (key, annotation, elem)
+        elif mapped_container is not None:
+            # it's Mapped[], but there's no "element", which means declarative
+            # did not actually do anything for this field.  this shouldn't
+            # happen.
+            # previously, this would occur because _scan_attributes would
+            # skip a field that's on an already mapped superclass, but it
+            # would still include it in the annotations, leading
+            # to issue #8718
+
+            assert False, "Mapped[] received without a mapping declaration"
+
+        else:
+            # plain dataclass field, not mapped.  Is only possible
+            # if __allow_unmapped__ is set up.  I can see this mode causing
+            # problems...
+            return (key, annotation)
+
+
+_DEFAULT_ATTRIBUTE_OPTIONS = _AttributeOptions(
+    _NoArg.NO_ARG,
+    _NoArg.NO_ARG,
+    _NoArg.NO_ARG,
+    _NoArg.NO_ARG,
+    _NoArg.NO_ARG,
+    _NoArg.NO_ARG,
+)
+
+_DEFAULT_READONLY_ATTRIBUTE_OPTIONS = _AttributeOptions(
+    False,
+    _NoArg.NO_ARG,
+    _NoArg.NO_ARG,
+    _NoArg.NO_ARG,
+    _NoArg.NO_ARG,
+    _NoArg.NO_ARG,
+)
+
+
+class _DCAttributeOptions:
+    """mixin for descriptors or configurational objects that include dataclass
+    field options.
+
+    This includes :class:`.MapperProperty`, :class:`._MapsColumn` within
+    the ORM, but also includes :class:`.AssociationProxy` within ext.
+    Can in theory be used for other descriptors that serve a similar role
+    as association proxy.   (*maybe* hybrids, not sure yet.)
+
+    """
+
+    __slots__ = ()
+
+    _attribute_options: _AttributeOptions
+    """behavioral options for ORM-enabled Python attributes
+
+    .. versionadded:: 2.0
+
+    """
+
+    _has_dataclass_arguments: bool
+
+
+class _MapsColumns(_DCAttributeOptions, _MappedAttribute[_T]):
+    """interface for declarative-capable construct that delivers one or more
+    Column objects to the declarative process to be part of a Table.
+    """
+
+    __slots__ = ()
+
+    @property
+    def mapper_property_to_assign(self) -> Optional[MapperProperty[_T]]:
+        """return a MapperProperty to be assigned to the declarative mapping"""
+        raise NotImplementedError()
+
+    @property
+    def columns_to_assign(self) -> List[Tuple[Column[_T], int]]:
+        """A list of Column objects that should be declaratively added to the
+        new Table object.
+
+        """
+        raise NotImplementedError()
+
+
+# NOTE: MapperProperty needs to extend _MappedAttribute so that declarative
+# typing works, i.e. "Mapped[A] = relationship()".   This introduces an
+# inconvenience which is that all the MapperProperty objects are treated
+# as descriptors by typing tools, which are misled by this as assignment /
+# access to a descriptor attribute wants to move through __get__.
+# Therefore, references to MapperProperty as an instance variable, such
+# as in PropComparator, may have some special typing workarounds such as the
+# use of sqlalchemy.util.typing.DescriptorReference to avoid mis-interpretation
+# by typing tools
+@inspection._self_inspects
+class MapperProperty(
+    HasCacheKey,
+    _DCAttributeOptions,
+    _MappedAttribute[_T],
+    InspectionAttrInfo,
+    util.MemoizedSlots,
+):
+    """Represent a particular class attribute mapped by :class:`_orm.Mapper`.
+
+    The most common occurrences of :class:`.MapperProperty` are the
+    mapped :class:`_schema.Column`, which is represented in a mapping as
+    an instance of :class:`.ColumnProperty`,
+    and a reference to another class produced by :func:`_orm.relationship`,
+    represented in the mapping as an instance of
+    :class:`.Relationship`.
+
+    """
+
+    __slots__ = (
+        "_configure_started",
+        "_configure_finished",
+        "_attribute_options",
+        "_has_dataclass_arguments",
+        "parent",
+        "key",
+        "info",
+        "doc",
+    )
+
+    _cache_key_traversal: _TraverseInternalsType = [
+        ("parent", visitors.ExtendedInternalTraversal.dp_has_cache_key),
+        ("key", visitors.ExtendedInternalTraversal.dp_string),
+    ]
+
+    if not TYPE_CHECKING:
+        cascade = None
+
+    is_property = True
+    """Part of the InspectionAttr interface; states this object is a
+    mapper property.
+
+    """
+
+    comparator: PropComparator[_T]
+    """The :class:`_orm.PropComparator` instance that implements SQL
+    expression construction on behalf of this mapped attribute."""
+
+    key: str
+    """name of class attribute"""
+
+    parent: Mapper[Any]
+    """the :class:`.Mapper` managing this property."""
+
+    _is_relationship = False
+
+    _links_to_entity: bool
+    """True if this MapperProperty refers to a mapped entity.
+
+    Should only be True for Relationship, False for all others.
+
+    """
+
+    doc: Optional[str]
+    """optional documentation string"""
+
+    info: _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.
+
+    .. seealso::
+
+        :attr:`.QueryableAttribute.info`
+
+        :attr:`.SchemaItem.info`
+
+    """
+
+    def _memoized_attr_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.
+
+        .. seealso::
+
+            :attr:`.QueryableAttribute.info`
+
+            :attr:`.SchemaItem.info`
+
+        """
+        return {}
+
+    def setup(
+        self,
+        context: ORMCompileState,
+        query_entity: _MapperEntity,
+        path: AbstractEntityRegistry,
+        adapter: Optional[ORMAdapter],
+        **kwargs: Any,
+    ) -> None:
+        """Called by Query for the purposes of constructing a SQL statement.
+
+        Each MapperProperty associated with the target mapper processes the
+        statement referenced by the query context, adding columns and/or
+        criterion as appropriate.
+
+        """
+
+    def create_row_processor(
+        self,
+        context: ORMCompileState,
+        query_entity: _MapperEntity,
+        path: AbstractEntityRegistry,
+        mapper: Mapper[Any],
+        result: Result[Any],
+        adapter: Optional[ORMAdapter],
+        populators: _PopulatorDict,
+    ) -> None:
+        """Produce row processing functions and append to the given
+        set of populators lists.
+
+        """
+
+    def cascade_iterator(
+        self,
+        type_: str,
+        state: InstanceState[Any],
+        dict_: _InstanceDict,
+        visited_states: Set[InstanceState[Any]],
+        halt_on: Optional[Callable[[InstanceState[Any]], bool]] = None,
+    ) -> Iterator[
+        Tuple[object, Mapper[Any], InstanceState[Any], _InstanceDict]
+    ]:
+        """Iterate through instances related to the given instance for
+        a particular 'cascade', starting with this MapperProperty.
+
+        Return an iterator3-tuples (instance, mapper, state).
+
+        Note that the 'cascade' collection on this MapperProperty is
+        checked first for the given type before cascade_iterator is called.
+
+        This method typically only applies to Relationship.
+
+        """
+
+        return iter(())
+
+    def set_parent(self, parent: Mapper[Any], init: bool) -> None:
+        """Set the parent mapper that references this MapperProperty.
+
+        This method is overridden by some subclasses to perform extra
+        setup when the mapper is first known.
+
+        """
+        self.parent = parent
+
+    def instrument_class(self, mapper: Mapper[Any]) -> None:
+        """Hook called by the Mapper to the property to initiate
+        instrumentation of the class attribute managed by this
+        MapperProperty.
+
+        The MapperProperty here will typically call out to the
+        attributes module to set up an InstrumentedAttribute.
+
+        This step is the first of two steps to set up an InstrumentedAttribute,
+        and is called early in the mapper setup process.
+
+        The second step is typically the init_class_attribute step,
+        called from StrategizedProperty via the post_instrument_class()
+        hook.  This step assigns additional state to the InstrumentedAttribute
+        (specifically the "impl") which has been determined after the
+        MapperProperty has determined what kind of persistence
+        management it needs to do (e.g. scalar, object, collection, etc).
+
+        """
+
+    def __init__(
+        self,
+        attribute_options: Optional[_AttributeOptions] = None,
+        _assume_readonly_dc_attributes: bool = False,
+    ) -> None:
+        self._configure_started = False
+        self._configure_finished = False
+
+        if _assume_readonly_dc_attributes:
+            default_attrs = _DEFAULT_READONLY_ATTRIBUTE_OPTIONS
+        else:
+            default_attrs = _DEFAULT_ATTRIBUTE_OPTIONS
+
+        if attribute_options and attribute_options != default_attrs:
+            self._has_dataclass_arguments = True
+            self._attribute_options = attribute_options
+        else:
+            self._has_dataclass_arguments = False
+            self._attribute_options = default_attrs
+
+    def init(self) -> None:
+        """Called after all mappers are created to assemble
+        relationships between mappers and perform other post-mapper-creation
+        initialization steps.
+
+
+        """
+        self._configure_started = True
+        self.do_init()
+        self._configure_finished = True
+
+    @property
+    def class_attribute(self) -> InstrumentedAttribute[_T]:
+        """Return the class-bound descriptor corresponding to this
+        :class:`.MapperProperty`.
+
+        This is basically a ``getattr()`` call::
+
+            return getattr(self.parent.class_, self.key)
+
+        I.e. if this :class:`.MapperProperty` were named ``addresses``,
+        and the class to which it is mapped is ``User``, this sequence
+        is possible::
+
+            >>> from sqlalchemy import inspect
+            >>> mapper = inspect(User)
+            >>> addresses_property = mapper.attrs.addresses
+            >>> addresses_property.class_attribute is User.addresses
+            True
+            >>> User.addresses.property is addresses_property
+            True
+
+
+        """
+
+        return getattr(self.parent.class_, self.key)  # type: ignore
+
+    def do_init(self) -> None:
+        """Perform subclass-specific initialization post-mapper-creation
+        steps.
+
+        This is a template method called by the ``MapperProperty``
+        object's init() method.
+
+        """
+
+    def post_instrument_class(self, mapper: Mapper[Any]) -> None:
+        """Perform instrumentation adjustments that need to occur
+        after init() has completed.
+
+        The given Mapper is the Mapper invoking the operation, which
+        may not be the same Mapper as self.parent in an inheritance
+        scenario; however, Mapper will always at least be a sub-mapper of
+        self.parent.
+
+        This method is typically used by StrategizedProperty, which delegates
+        it to LoaderStrategy.init_class_attribute() to perform final setup
+        on the class-bound InstrumentedAttribute.
+
+        """
+
+    def merge(
+        self,
+        session: Session,
+        source_state: InstanceState[Any],
+        source_dict: _InstanceDict,
+        dest_state: InstanceState[Any],
+        dest_dict: _InstanceDict,
+        load: bool,
+        _recursive: Dict[Any, object],
+        _resolve_conflict_map: Dict[_IdentityKeyType[Any], object],
+    ) -> None:
+        """Merge the attribute represented by this ``MapperProperty``
+        from source to destination object.
+
+        """
+
+    def __repr__(self) -> str:
+        return "<%s at 0x%x; %s>" % (
+            self.__class__.__name__,
+            id(self),
+            getattr(self, "key", "no key"),
+        )
+
+
+@inspection._self_inspects
+class PropComparator(SQLORMOperations[_T_co], Generic[_T_co], ColumnOperators):
+    r"""Defines SQL operations for ORM mapped attributes.
+
+    SQLAlchemy allows for operators to
+    be redefined at both the Core and ORM level.  :class:`.PropComparator`
+    is the base class of operator redefinition for ORM-level operations,
+    including those of :class:`.ColumnProperty`,
+    :class:`.Relationship`, and :class:`.Composite`.
+
+    User-defined subclasses of :class:`.PropComparator` may be created. The
+    built-in Python comparison and math operator methods, such as
+    :meth:`.operators.ColumnOperators.__eq__`,
+    :meth:`.operators.ColumnOperators.__lt__`, and
+    :meth:`.operators.ColumnOperators.__add__`, can be overridden to provide
+    new operator behavior. The custom :class:`.PropComparator` is passed to
+    the :class:`.MapperProperty` instance via the ``comparator_factory``
+    argument. In each case,
+    the appropriate subclass of :class:`.PropComparator` should be used::
+
+        # definition of custom PropComparator subclasses
+
+        from sqlalchemy.orm.properties import \
+                                ColumnProperty,\
+                                Composite,\
+                                Relationship
+
+        class MyColumnComparator(ColumnProperty.Comparator):
+            def __eq__(self, other):
+                return self.__clause_element__() == other
+
+        class MyRelationshipComparator(Relationship.Comparator):
+            def any(self, expression):
+                "define the 'any' operation"
+                # ...
+
+        class MyCompositeComparator(Composite.Comparator):
+            def __gt__(self, other):
+                "redefine the 'greater than' operation"
+
+                return sql.and_(*[a>b for a, b in
+                                  zip(self.__clause_element__().clauses,
+                                      other.__composite_values__())])
+
+
+        # application of custom PropComparator subclasses
+
+        from sqlalchemy.orm import column_property, relationship, composite
+        from sqlalchemy import Column, String
+
+        class SomeMappedClass(Base):
+            some_column = column_property(Column("some_column", String),
+                                comparator_factory=MyColumnComparator)
+
+            some_relationship = relationship(SomeOtherClass,
+                                comparator_factory=MyRelationshipComparator)
+
+            some_composite = composite(
+                    Column("a", String), Column("b", String),
+                    comparator_factory=MyCompositeComparator
+                )
+
+    Note that for column-level operator redefinition, it's usually
+    simpler to define the operators at the Core level, using the
+    :attr:`.TypeEngine.comparator_factory` attribute.  See
+    :ref:`types_operators` for more detail.
+
+    .. seealso::
+
+        :class:`.ColumnProperty.Comparator`
+
+        :class:`.Relationship.Comparator`
+
+        :class:`.Composite.Comparator`
+
+        :class:`.ColumnOperators`
+
+        :ref:`types_operators`
+
+        :attr:`.TypeEngine.comparator_factory`
+
+    """
+
+    __slots__ = "prop", "_parententity", "_adapt_to_entity"
+
+    __visit_name__ = "orm_prop_comparator"
+
+    _parententity: _InternalEntityType[Any]
+    _adapt_to_entity: Optional[AliasedInsp[Any]]
+    prop: RODescriptorReference[MapperProperty[_T_co]]
+
+    def __init__(
+        self,
+        prop: MapperProperty[_T],
+        parentmapper: _InternalEntityType[Any],
+        adapt_to_entity: Optional[AliasedInsp[Any]] = None,
+    ):
+        self.prop = prop
+        self._parententity = adapt_to_entity or parentmapper
+        self._adapt_to_entity = adapt_to_entity
+
+    @util.non_memoized_property
+    def property(self) -> MapperProperty[_T_co]:
+        """Return the :class:`.MapperProperty` associated with this
+        :class:`.PropComparator`.
+
+
+        Return values here will commonly be instances of
+        :class:`.ColumnProperty` or :class:`.Relationship`.
+
+
+        """
+        return self.prop
+
+    def __clause_element__(self) -> roles.ColumnsClauseRole:
+        raise NotImplementedError("%r" % self)
+
+    def _bulk_update_tuples(
+        self, value: Any
+    ) -> Sequence[Tuple[_DMLColumnArgument, Any]]:
+        """Receive a SQL expression that represents a value in the SET
+        clause of an UPDATE statement.
+
+        Return a tuple that can be passed to a :class:`_expression.Update`
+        construct.
+
+        """
+
+        return [(cast("_DMLColumnArgument", self.__clause_element__()), value)]
+
+    def adapt_to_entity(
+        self, adapt_to_entity: AliasedInsp[Any]
+    ) -> PropComparator[_T_co]:
+        """Return a copy of this PropComparator which will use the given
+        :class:`.AliasedInsp` to produce corresponding expressions.
+        """
+        return self.__class__(self.prop, self._parententity, adapt_to_entity)
+
+    @util.ro_non_memoized_property
+    def _parentmapper(self) -> Mapper[Any]:
+        """legacy; this is renamed to _parententity to be
+        compatible with QueryableAttribute."""
+        return self._parententity.mapper
+
+    def _criterion_exists(
+        self,
+        criterion: Optional[_ColumnExpressionArgument[bool]] = None,
+        **kwargs: Any,
+    ) -> ColumnElement[Any]:
+        return self.prop.comparator._criterion_exists(criterion, **kwargs)
+
+    @util.ro_non_memoized_property
+    def adapter(self) -> Optional[_ORMAdapterProto]:
+        """Produce a callable that adapts column expressions
+        to suit an aliased version of this comparator.
+
+        """
+        if self._adapt_to_entity is None:
+            return None
+        else:
+            return self._adapt_to_entity._orm_adapt_element
+
+    @util.ro_non_memoized_property
+    def info(self) -> _InfoType:
+        return self.prop.info
+
+    @staticmethod
+    def _any_op(a: Any, b: Any, **kwargs: Any) -> Any:
+        return a.any(b, **kwargs)
+
+    @staticmethod
+    def _has_op(left: Any, other: Any, **kwargs: Any) -> Any:
+        return left.has(other, **kwargs)
+
+    @staticmethod
+    def _of_type_op(a: Any, class_: Any) -> Any:
+        return a.of_type(class_)
+
+    any_op = cast(operators.OperatorType, _any_op)
+    has_op = cast(operators.OperatorType, _has_op)
+    of_type_op = cast(operators.OperatorType, _of_type_op)
+
+    if typing.TYPE_CHECKING:
+
+        def operate(
+            self, op: OperatorType, *other: Any, **kwargs: Any
+        ) -> ColumnElement[Any]: ...
+
+        def reverse_operate(
+            self, op: OperatorType, other: Any, **kwargs: Any
+        ) -> ColumnElement[Any]: ...
+
+    def of_type(self, class_: _EntityType[Any]) -> PropComparator[_T_co]:
+        r"""Redefine this object in terms of a polymorphic subclass,
+        :func:`_orm.with_polymorphic` construct, or :func:`_orm.aliased`
+        construct.
+
+        Returns a new PropComparator from which further criterion can be
+        evaluated.
+
+        e.g.::
+
+            query.join(Company.employees.of_type(Engineer)).\
+               filter(Engineer.name=='foo')
+
+        :param \class_: a class or mapper indicating that criterion will be
+            against this specific subclass.
+
+        .. seealso::
+
+            :ref:`orm_queryguide_joining_relationships_aliased` - in the
+            :ref:`queryguide_toplevel`
+
+            :ref:`inheritance_of_type`
+
+        """
+
+        return self.operate(PropComparator.of_type_op, class_)  # type: ignore
+
+    def and_(
+        self, *criteria: _ColumnExpressionArgument[bool]
+    ) -> PropComparator[bool]:
+        """Add additional criteria to the ON clause that's represented by this
+        relationship attribute.
+
+        E.g.::
+
+
+            stmt = select(User).join(
+                User.addresses.and_(Address.email_address != 'foo')
+            )
+
+            stmt = select(User).options(
+                joinedload(User.addresses.and_(Address.email_address != 'foo'))
+            )
+
+        .. versionadded:: 1.4
+
+        .. seealso::
+
+            :ref:`orm_queryguide_join_on_augmented`
+
+            :ref:`loader_option_criteria`
+
+            :func:`.with_loader_criteria`
+
+        """
+        return self.operate(operators.and_, *criteria)  # type: ignore
+
+    def any(
+        self,
+        criterion: Optional[_ColumnExpressionArgument[bool]] = None,
+        **kwargs: Any,
+    ) -> ColumnElement[bool]:
+        r"""Return a SQL expression representing true if this element
+        references a member which meets the given criterion.
+
+        The usual implementation of ``any()`` is
+        :meth:`.Relationship.Comparator.any`.
+
+        :param criterion: an optional ClauseElement formulated against the
+          member class' table or attributes.
+
+        :param \**kwargs: key/value pairs corresponding to member class
+          attribute names which will be compared via equality to the
+          corresponding values.
+
+        """
+
+        return self.operate(PropComparator.any_op, criterion, **kwargs)
+
+    def has(
+        self,
+        criterion: Optional[_ColumnExpressionArgument[bool]] = None,
+        **kwargs: Any,
+    ) -> ColumnElement[bool]:
+        r"""Return a SQL expression representing true if this element
+        references a member which meets the given criterion.
+
+        The usual implementation of ``has()`` is
+        :meth:`.Relationship.Comparator.has`.
+
+        :param criterion: an optional ClauseElement formulated against the
+          member class' table or attributes.
+
+        :param \**kwargs: key/value pairs corresponding to member class
+          attribute names which will be compared via equality to the
+          corresponding values.
+
+        """
+
+        return self.operate(PropComparator.has_op, criterion, **kwargs)
+
+
+class StrategizedProperty(MapperProperty[_T]):
+    """A MapperProperty which uses selectable strategies to affect
+    loading behavior.
+
+    There is a single strategy selected by default.  Alternate
+    strategies can be selected at Query time through the usage of
+    ``StrategizedOption`` objects via the Query.options() method.
+
+    The mechanics of StrategizedProperty are used for every Query
+    invocation for every mapped attribute participating in that Query,
+    to determine first how the attribute will be rendered in SQL
+    and secondly how the attribute will retrieve a value from a result
+    row and apply it to a mapped object.  The routines here are very
+    performance-critical.
+
+    """
+
+    __slots__ = (
+        "_strategies",
+        "strategy",
+        "_wildcard_token",
+        "_default_path_loader_key",
+        "strategy_key",
+    )
+    inherit_cache = True
+    strategy_wildcard_key: ClassVar[str]
+
+    strategy_key: _StrategyKey
+
+    _strategies: Dict[_StrategyKey, LoaderStrategy]
+
+    def _memoized_attr__wildcard_token(self) -> Tuple[str]:
+        return (
+            f"{self.strategy_wildcard_key}:{path_registry._WILDCARD_TOKEN}",
+        )
+
+    def _memoized_attr__default_path_loader_key(
+        self,
+    ) -> Tuple[str, Tuple[str]]:
+        return (
+            "loader",
+            (f"{self.strategy_wildcard_key}:{path_registry._DEFAULT_TOKEN}",),
+        )
+
+    def _get_context_loader(
+        self, context: ORMCompileState, path: AbstractEntityRegistry
+    ) -> Optional[_LoadElement]:
+        load: Optional[_LoadElement] = None
+
+        search_path = path[self]
+
+        # search among: exact match, "attr.*", "default" strategy
+        # if any.
+        for path_key in (
+            search_path._loader_key,
+            search_path._wildcard_path_loader_key,
+            search_path._default_path_loader_key,
+        ):
+            if path_key in context.attributes:
+                load = context.attributes[path_key]
+                break
+
+                # note that if strategy_options.Load is placing non-actionable
+                # objects in the context like defaultload(), we would
+                # need to continue the loop here if we got such an
+                # option as below.
+                # if load.strategy or load.local_opts:
+                #    break
+
+        return load
+
+    def _get_strategy(self, key: _StrategyKey) -> LoaderStrategy:
+        try:
+            return self._strategies[key]
+        except KeyError:
+            pass
+
+        # run outside to prevent transfer of exception context
+        cls = self._strategy_lookup(self, *key)
+        # this previously was setting self._strategies[cls], that's
+        # a bad idea; should use strategy key at all times because every
+        # strategy has multiple keys at this point
+        self._strategies[key] = strategy = cls(self, key)
+        return strategy
+
+    def setup(
+        self,
+        context: ORMCompileState,
+        query_entity: _MapperEntity,
+        path: AbstractEntityRegistry,
+        adapter: Optional[ORMAdapter],
+        **kwargs: Any,
+    ) -> None:
+        loader = self._get_context_loader(context, path)
+        if loader and loader.strategy:
+            strat = self._get_strategy(loader.strategy)
+        else:
+            strat = self.strategy
+        strat.setup_query(
+            context, query_entity, path, loader, adapter, **kwargs
+        )
+
+    def create_row_processor(
+        self,
+        context: ORMCompileState,
+        query_entity: _MapperEntity,
+        path: AbstractEntityRegistry,
+        mapper: Mapper[Any],
+        result: Result[Any],
+        adapter: Optional[ORMAdapter],
+        populators: _PopulatorDict,
+    ) -> None:
+        loader = self._get_context_loader(context, path)
+        if loader and loader.strategy:
+            strat = self._get_strategy(loader.strategy)
+        else:
+            strat = self.strategy
+        strat.create_row_processor(
+            context,
+            query_entity,
+            path,
+            loader,
+            mapper,
+            result,
+            adapter,
+            populators,
+        )
+
+    def do_init(self) -> None:
+        self._strategies = {}
+        self.strategy = self._get_strategy(self.strategy_key)
+
+    def post_instrument_class(self, mapper: Mapper[Any]) -> None:
+        if (
+            not self.parent.non_primary
+            and not mapper.class_manager._attr_has_impl(self.key)
+        ):
+            self.strategy.init_class_attribute(mapper)
+
+    _all_strategies: collections.defaultdict[
+        Type[MapperProperty[Any]], Dict[_StrategyKey, Type[LoaderStrategy]]
+    ] = collections.defaultdict(dict)
+
+    @classmethod
+    def strategy_for(cls, **kw: Any) -> Callable[[_TLS], _TLS]:
+        def decorate(dec_cls: _TLS) -> _TLS:
+            # ensure each subclass of the strategy has its
+            # own _strategy_keys collection
+            if "_strategy_keys" not in dec_cls.__dict__:
+                dec_cls._strategy_keys = []
+            key = tuple(sorted(kw.items()))
+            cls._all_strategies[cls][key] = dec_cls
+            dec_cls._strategy_keys.append(key)
+            return dec_cls
+
+        return decorate
+
+    @classmethod
+    def _strategy_lookup(
+        cls, requesting_property: MapperProperty[Any], *key: Any
+    ) -> Type[LoaderStrategy]:
+        requesting_property.parent._with_polymorphic_mappers
+
+        for prop_cls in cls.__mro__:
+            if prop_cls in cls._all_strategies:
+                if TYPE_CHECKING:
+                    assert issubclass(prop_cls, MapperProperty)
+                strategies = cls._all_strategies[prop_cls]
+                try:
+                    return strategies[key]
+                except KeyError:
+                    pass
+
+        for property_type, strats in cls._all_strategies.items():
+            if key in strats:
+                intended_property_type = property_type
+                actual_strategy = strats[key]
+                break
+        else:
+            intended_property_type = None
+            actual_strategy = None
+
+        raise orm_exc.LoaderStrategyException(
+            cls,
+            requesting_property,
+            intended_property_type,
+            actual_strategy,
+            key,
+        )
+
+
+class ORMOption(ExecutableOption):
+    """Base class for option objects that are passed to ORM queries.
+
+    These options may be consumed by :meth:`.Query.options`,
+    :meth:`.Select.options`, or in a more general sense by any
+    :meth:`.Executable.options` method.   They are interpreted at
+    statement compile time or execution time in modern use.  The
+    deprecated :class:`.MapperOption` is consumed at ORM query construction
+    time.
+
+    .. versionadded:: 1.4
+
+    """
+
+    __slots__ = ()
+
+    _is_legacy_option = False
+
+    propagate_to_loaders = False
+    """if True, indicate this option should be carried along
+    to "secondary" SELECT statements that occur for relationship
+    lazy loaders as well as attribute load / refresh operations.
+
+    """
+
+    _is_core = False
+
+    _is_user_defined = False
+
+    _is_compile_state = False
+
+    _is_criteria_option = False
+
+    _is_strategy_option = False
+
+    def _adapt_cached_option_to_uncached_option(
+        self, context: QueryContext, uncached_opt: ORMOption
+    ) -> ORMOption:
+        """adapt this option to the "uncached" version of itself in a
+        loader strategy context.
+
+        given "self" which is an option from a cached query, as well as the
+        corresponding option from the uncached version of the same query,
+        return the option we should use in a new query, in the context of a
+        loader strategy being asked to load related rows on behalf of that
+        cached query, which is assumed to be building a new query based on
+        entities passed to us from the cached query.
+
+        Currently this routine chooses between "self" and "uncached" without
+        manufacturing anything new. If the option is itself a loader strategy
+        option which has a path, that path needs to match to the entities being
+        passed to us by the cached query, so the :class:`_orm.Load` subclass
+        overrides this to return "self". For all other options, we return the
+        uncached form which may have changing state, such as a
+        with_loader_criteria() option which will very often have new state.
+
+        This routine could in the future involve
+        generating a new option based on both inputs if use cases arise,
+        such as if with_loader_criteria() needed to match up to
+        ``AliasedClass`` instances given in the parent query.
+
+        However, longer term it might be better to restructure things such that
+        ``AliasedClass`` entities are always matched up on their cache key,
+        instead of identity, in things like paths and such, so that this whole
+        issue of "the uncached option does not match the entities" goes away.
+        However this would make ``PathRegistry`` more complicated and difficult
+        to debug as well as potentially less performant in that it would be
+        hashing enormous cache keys rather than a simple AliasedInsp. UNLESS,
+        we could get cache keys overall to be reliably hashed into something
+        like an md5 key.
+
+        .. versionadded:: 1.4.41
+
+        """
+        if uncached_opt is not None:
+            return uncached_opt
+        else:
+            return self
+
+
+class CompileStateOption(HasCacheKey, ORMOption):
+    """base for :class:`.ORMOption` classes that affect the compilation of
+    a SQL query and therefore need to be part of the cache key.
+
+    .. note::  :class:`.CompileStateOption` is generally non-public and
+       should not be used as a base class for user-defined options; instead,
+       use :class:`.UserDefinedOption`, which is easier to use as it does not
+       interact with ORM compilation internals or caching.
+
+    :class:`.CompileStateOption` defines an internal attribute
+    ``_is_compile_state=True`` which has the effect of the ORM compilation
+    routines for SELECT and other statements will call upon these options when
+    a SQL string is being compiled. As such, these classes implement
+    :class:`.HasCacheKey` and need to provide robust ``_cache_key_traversal``
+    structures.
+
+    The :class:`.CompileStateOption` class is used to implement the ORM
+    :class:`.LoaderOption` and :class:`.CriteriaOption` classes.
+
+    .. versionadded:: 1.4.28
+
+
+    """
+
+    __slots__ = ()
+
+    _is_compile_state = True
+
+    def process_compile_state(self, compile_state: ORMCompileState) -> None:
+        """Apply a modification to a given :class:`.ORMCompileState`.
+
+        This method is part of the implementation of a particular
+        :class:`.CompileStateOption` and is only invoked internally
+        when an ORM query is compiled.
+
+        """
+
+    def process_compile_state_replaced_entities(
+        self,
+        compile_state: ORMCompileState,
+        mapper_entities: Sequence[_MapperEntity],
+    ) -> None:
+        """Apply a modification to a given :class:`.ORMCompileState`,
+        given entities that were replaced by with_only_columns() or
+        with_entities().
+
+        This method is part of the implementation of a particular
+        :class:`.CompileStateOption` and is only invoked internally
+        when an ORM query is compiled.
+
+        .. versionadded:: 1.4.19
+
+        """
+
+
+class LoaderOption(CompileStateOption):
+    """Describe a loader modification to an ORM statement at compilation time.
+
+    .. versionadded:: 1.4
+
+    """
+
+    __slots__ = ()
+
+    def process_compile_state_replaced_entities(
+        self,
+        compile_state: ORMCompileState,
+        mapper_entities: Sequence[_MapperEntity],
+    ) -> None:
+        self.process_compile_state(compile_state)
+
+
+class CriteriaOption(CompileStateOption):
+    """Describe a WHERE criteria modification to an ORM statement at
+    compilation time.
+
+    .. versionadded:: 1.4
+
+    """
+
+    __slots__ = ()
+
+    _is_criteria_option = True
+
+    def get_global_criteria(self, attributes: Dict[str, Any]) -> None:
+        """update additional entity criteria options in the given
+        attributes dictionary.
+
+        """
+
+
+class UserDefinedOption(ORMOption):
+    """Base class for a user-defined option that can be consumed from the
+    :meth:`.SessionEvents.do_orm_execute` event hook.
+
+    """
+
+    __slots__ = ("payload",)
+
+    _is_legacy_option = False
+
+    _is_user_defined = True
+
+    propagate_to_loaders = False
+    """if True, indicate this option should be carried along
+    to "secondary" Query objects produced during lazy loads
+    or refresh operations.
+
+    """
+
+    def __init__(self, payload: Optional[Any] = None):
+        self.payload = payload
+
+
+@util.deprecated_cls(
+    "1.4",
+    "The :class:`.MapperOption class is deprecated and will be removed "
+    "in a future release.   For "
+    "modifications to queries on a per-execution basis, use the "
+    ":class:`.UserDefinedOption` class to establish state within a "
+    ":class:`.Query` or other Core statement, then use the "
+    ":meth:`.SessionEvents.before_orm_execute` hook to consume them.",
+    constructor=None,
+)
+class MapperOption(ORMOption):
+    """Describe a modification to a Query"""
+
+    __slots__ = ()
+
+    _is_legacy_option = True
+
+    propagate_to_loaders = False
+    """if True, indicate this option should be carried along
+    to "secondary" Query objects produced during lazy loads
+    or refresh operations.
+
+    """
+
+    def process_query(self, query: Query[Any]) -> None:
+        """Apply a modification to the given :class:`_query.Query`."""
+
+    def process_query_conditionally(self, query: Query[Any]) -> None:
+        """same as process_query(), except that this option may not
+        apply to the given query.
+
+        This is typically applied during a lazy load or scalar refresh
+        operation to propagate options stated in the original Query to the
+        new Query being used for the load.  It occurs for those options that
+        specify propagate_to_loaders=True.
+
+        """
+
+        self.process_query(query)
+
+
+class LoaderStrategy:
+    """Describe the loading behavior of a StrategizedProperty object.
+
+    The ``LoaderStrategy`` interacts with the querying process in three
+    ways:
+
+    * it controls the configuration of the ``InstrumentedAttribute``
+      placed on a class to handle the behavior of the attribute.  this
+      may involve setting up class-level callable functions to fire
+      off a select operation when the attribute is first accessed
+      (i.e. a lazy load)
+
+    * it processes the ``QueryContext`` at statement construction time,
+      where it can modify the SQL statement that is being produced.
+      For example, simple column attributes will add their represented
+      column to the list of selected columns, a joined eager loader
+      may establish join clauses to add to the statement.
+
+    * It produces "row processor" functions at result fetching time.
+      These "row processor" functions populate a particular attribute
+      on a particular mapped instance.
+
+    """
+
+    __slots__ = (
+        "parent_property",
+        "is_class_level",
+        "parent",
+        "key",
+        "strategy_key",
+        "strategy_opts",
+    )
+
+    _strategy_keys: ClassVar[List[_StrategyKey]]
+
+    def __init__(
+        self, parent: MapperProperty[Any], strategy_key: _StrategyKey
+    ):
+        self.parent_property = parent
+        self.is_class_level = False
+        self.parent = self.parent_property.parent
+        self.key = self.parent_property.key
+        self.strategy_key = strategy_key
+        self.strategy_opts = dict(strategy_key)
+
+    def init_class_attribute(self, mapper: Mapper[Any]) -> None:
+        pass
+
+    def setup_query(
+        self,
+        compile_state: ORMCompileState,
+        query_entity: _MapperEntity,
+        path: AbstractEntityRegistry,
+        loadopt: Optional[_LoadElement],
+        adapter: Optional[ORMAdapter],
+        **kwargs: Any,
+    ) -> None:
+        """Establish column and other state for a given QueryContext.
+
+        This method fulfills the contract specified by MapperProperty.setup().
+
+        StrategizedProperty delegates its setup() method
+        directly to this method.
+
+        """
+
+    def create_row_processor(
+        self,
+        context: ORMCompileState,
+        query_entity: _MapperEntity,
+        path: AbstractEntityRegistry,
+        loadopt: Optional[_LoadElement],
+        mapper: Mapper[Any],
+        result: Result[Any],
+        adapter: Optional[ORMAdapter],
+        populators: _PopulatorDict,
+    ) -> None:
+        """Establish row processing functions for a given QueryContext.
+
+        This method fulfills the contract specified by
+        MapperProperty.create_row_processor().
+
+        StrategizedProperty delegates its create_row_processor() method
+        directly to this method.
+
+        """
+
+    def __str__(self) -> str:
+        return str(self.parent_property)