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# orm/mapped_collection.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
from __future__ import annotations
import operator
from typing import Any
from typing import Callable
from typing import Dict
from typing import Generic
from typing import List
from typing import Optional
from typing import Sequence
from typing import Tuple
from typing import Type
from typing import TYPE_CHECKING
from typing import TypeVar
from typing import Union
from . import base
from .collections import collection
from .collections import collection_adapter
from .. import exc as sa_exc
from .. import util
from ..sql import coercions
from ..sql import expression
from ..sql import roles
from ..util.langhelpers import Missing
from ..util.langhelpers import MissingOr
from ..util.typing import Literal
if TYPE_CHECKING:
from . import AttributeEventToken
from . import Mapper
from .collections import CollectionAdapter
from ..sql.elements import ColumnElement
_KT = TypeVar("_KT", bound=Any)
_VT = TypeVar("_VT", bound=Any)
class _PlainColumnGetter(Generic[_KT]):
"""Plain column getter, stores collection of Column objects
directly.
Serializes to a :class:`._SerializableColumnGetterV2`
which has more expensive __call__() performance
and some rare caveats.
"""
__slots__ = ("cols", "composite")
def __init__(self, cols: Sequence[ColumnElement[_KT]]) -> None:
self.cols = cols
self.composite = len(cols) > 1
def __reduce__(
self,
) -> Tuple[
Type[_SerializableColumnGetterV2[_KT]],
Tuple[Sequence[Tuple[Optional[str], Optional[str]]]],
]:
return _SerializableColumnGetterV2._reduce_from_cols(self.cols)
def _cols(self, mapper: Mapper[_KT]) -> Sequence[ColumnElement[_KT]]:
return self.cols
def __call__(self, value: _KT) -> MissingOr[Union[_KT, Tuple[_KT, ...]]]:
state = base.instance_state(value)
m = base._state_mapper(state)
key: List[_KT] = [
m._get_state_attr_by_column(state, state.dict, col)
for col in self._cols(m)
]
if self.composite:
return tuple(key)
else:
obj = key[0]
if obj is None:
return Missing
else:
return obj
class _SerializableColumnGetterV2(_PlainColumnGetter[_KT]):
"""Updated serializable getter which deals with
multi-table mapped classes.
Two extremely unusual cases are not supported.
Mappings which have tables across multiple metadata
objects, or which are mapped to non-Table selectables
linked across inheriting mappers may fail to function
here.
"""
__slots__ = ("colkeys",)
def __init__(
self, colkeys: Sequence[Tuple[Optional[str], Optional[str]]]
) -> None:
self.colkeys = colkeys
self.composite = len(colkeys) > 1
def __reduce__(
self,
) -> Tuple[
Type[_SerializableColumnGetterV2[_KT]],
Tuple[Sequence[Tuple[Optional[str], Optional[str]]]],
]:
return self.__class__, (self.colkeys,)
@classmethod
def _reduce_from_cols(cls, cols: Sequence[ColumnElement[_KT]]) -> Tuple[
Type[_SerializableColumnGetterV2[_KT]],
Tuple[Sequence[Tuple[Optional[str], Optional[str]]]],
]:
def _table_key(c: ColumnElement[_KT]) -> Optional[str]:
if not isinstance(c.table, expression.TableClause):
return None
else:
return c.table.key # type: ignore
colkeys = [(c.key, _table_key(c)) for c in cols]
return _SerializableColumnGetterV2, (colkeys,)
def _cols(self, mapper: Mapper[_KT]) -> Sequence[ColumnElement[_KT]]:
cols: List[ColumnElement[_KT]] = []
metadata = getattr(mapper.local_table, "metadata", None)
for ckey, tkey in self.colkeys:
if tkey is None or metadata is None or tkey not in metadata:
cols.append(mapper.local_table.c[ckey]) # type: ignore
else:
cols.append(metadata.tables[tkey].c[ckey])
return cols
def column_keyed_dict(
mapping_spec: Union[Type[_KT], Callable[[_KT], _VT]],
*,
ignore_unpopulated_attribute: bool = False,
) -> Type[KeyFuncDict[_KT, _KT]]:
"""A dictionary-based collection type with column-based keying.
.. versionchanged:: 2.0 Renamed :data:`.column_mapped_collection` to
:class:`.column_keyed_dict`.
Returns a :class:`.KeyFuncDict` factory which will produce new
dictionary keys based on the value of a particular :class:`.Column`-mapped
attribute on ORM mapped instances to be added to the dictionary.
.. note:: the value of the target attribute must be assigned with its
value at the time that the object is being added to the
dictionary collection. Additionally, changes to the key attribute
are **not tracked**, which means the key in the dictionary is not
automatically synchronized with the key value on the target object
itself. See :ref:`key_collections_mutations` for further details.
.. seealso::
:ref:`orm_dictionary_collection` - background on use
:param mapping_spec: a :class:`_schema.Column` object that is expected
to be mapped by the target mapper to a particular attribute on the
mapped class, the value of which on a particular instance is to be used
as the key for a new dictionary entry for that instance.
:param ignore_unpopulated_attribute: if True, and the mapped attribute
indicated by the given :class:`_schema.Column` target attribute
on an object is not populated at all, the operation will be silently
skipped. By default, an error is raised.
.. versionadded:: 2.0 an error is raised by default if the attribute
being used for the dictionary key is determined that it was never
populated with any value. The
:paramref:`_orm.column_keyed_dict.ignore_unpopulated_attribute`
parameter may be set which will instead indicate that this condition
should be ignored, and the append operation silently skipped.
This is in contrast to the behavior of the 1.x series which would
erroneously populate the value in the dictionary with an arbitrary key
value of ``None``.
"""
cols = [
coercions.expect(roles.ColumnArgumentRole, q, argname="mapping_spec")
for q in util.to_list(mapping_spec)
]
keyfunc = _PlainColumnGetter(cols)
return _mapped_collection_cls(
keyfunc,
ignore_unpopulated_attribute=ignore_unpopulated_attribute,
)
class _AttrGetter:
__slots__ = ("attr_name", "getter")
def __init__(self, attr_name: str):
self.attr_name = attr_name
self.getter = operator.attrgetter(attr_name)
def __call__(self, mapped_object: Any) -> Any:
obj = self.getter(mapped_object)
if obj is None:
state = base.instance_state(mapped_object)
mp = state.mapper
if self.attr_name in mp.attrs:
dict_ = state.dict
obj = dict_.get(self.attr_name, base.NO_VALUE)
if obj is None:
return Missing
else:
return Missing
return obj
def __reduce__(self) -> Tuple[Type[_AttrGetter], Tuple[str]]:
return _AttrGetter, (self.attr_name,)
def attribute_keyed_dict(
attr_name: str, *, ignore_unpopulated_attribute: bool = False
) -> Type[KeyFuncDict[Any, Any]]:
"""A dictionary-based collection type with attribute-based keying.
.. versionchanged:: 2.0 Renamed :data:`.attribute_mapped_collection` to
:func:`.attribute_keyed_dict`.
Returns a :class:`.KeyFuncDict` factory which will produce new
dictionary keys based on the value of a particular named attribute on
ORM mapped instances to be added to the dictionary.
.. note:: the value of the target attribute must be assigned with its
value at the time that the object is being added to the
dictionary collection. Additionally, changes to the key attribute
are **not tracked**, which means the key in the dictionary is not
automatically synchronized with the key value on the target object
itself. See :ref:`key_collections_mutations` for further details.
.. seealso::
:ref:`orm_dictionary_collection` - background on use
:param attr_name: string name of an ORM-mapped attribute
on the mapped class, the value of which on a particular instance
is to be used as the key for a new dictionary entry for that instance.
:param ignore_unpopulated_attribute: if True, and the target attribute
on an object is not populated at all, the operation will be silently
skipped. By default, an error is raised.
.. versionadded:: 2.0 an error is raised by default if the attribute
being used for the dictionary key is determined that it was never
populated with any value. The
:paramref:`_orm.attribute_keyed_dict.ignore_unpopulated_attribute`
parameter may be set which will instead indicate that this condition
should be ignored, and the append operation silently skipped.
This is in contrast to the behavior of the 1.x series which would
erroneously populate the value in the dictionary with an arbitrary key
value of ``None``.
"""
return _mapped_collection_cls(
_AttrGetter(attr_name),
ignore_unpopulated_attribute=ignore_unpopulated_attribute,
)
def keyfunc_mapping(
keyfunc: Callable[[Any], Any],
*,
ignore_unpopulated_attribute: bool = False,
) -> Type[KeyFuncDict[_KT, Any]]:
"""A dictionary-based collection type with arbitrary keying.
.. versionchanged:: 2.0 Renamed :data:`.mapped_collection` to
:func:`.keyfunc_mapping`.
Returns a :class:`.KeyFuncDict` factory with a keying function
generated from keyfunc, a callable that takes an entity and returns a
key value.
.. note:: the given keyfunc is called only once at the time that the
target object is being added to the collection. Changes to the
effective value returned by the function are not tracked.
.. seealso::
:ref:`orm_dictionary_collection` - background on use
:param keyfunc: a callable that will be passed the ORM-mapped instance
which should then generate a new key to use in the dictionary.
If the value returned is :attr:`.LoaderCallableStatus.NO_VALUE`, an error
is raised.
:param ignore_unpopulated_attribute: if True, and the callable returns
:attr:`.LoaderCallableStatus.NO_VALUE` for a particular instance, the
operation will be silently skipped. By default, an error is raised.
.. versionadded:: 2.0 an error is raised by default if the callable
being used for the dictionary key returns
:attr:`.LoaderCallableStatus.NO_VALUE`, which in an ORM attribute
context indicates an attribute that was never populated with any value.
The :paramref:`_orm.mapped_collection.ignore_unpopulated_attribute`
parameter may be set which will instead indicate that this condition
should be ignored, and the append operation silently skipped. This is
in contrast to the behavior of the 1.x series which would erroneously
populate the value in the dictionary with an arbitrary key value of
``None``.
"""
return _mapped_collection_cls(
keyfunc, ignore_unpopulated_attribute=ignore_unpopulated_attribute
)
class KeyFuncDict(Dict[_KT, _VT]):
"""Base for ORM mapped dictionary classes.
Extends the ``dict`` type with additional methods needed by SQLAlchemy ORM
collection classes. Use of :class:`_orm.KeyFuncDict` is most directly
by using the :func:`.attribute_keyed_dict` or
:func:`.column_keyed_dict` class factories.
:class:`_orm.KeyFuncDict` may also serve as the base for user-defined
custom dictionary classes.
.. versionchanged:: 2.0 Renamed :class:`.MappedCollection` to
:class:`.KeyFuncDict`.
.. seealso::
:func:`_orm.attribute_keyed_dict`
:func:`_orm.column_keyed_dict`
:ref:`orm_dictionary_collection`
:ref:`orm_custom_collection`
"""
def __init__(
self,
keyfunc: Callable[[Any], Any],
*dict_args: Any,
ignore_unpopulated_attribute: bool = False,
) -> None:
"""Create a new collection with keying provided by keyfunc.
keyfunc may be any callable that takes an object and returns an object
for use as a dictionary key.
The keyfunc will be called every time the ORM needs to add a member by
value-only (such as when loading instances from the database) or
remove a member. The usual cautions about dictionary keying apply-
``keyfunc(object)`` should return the same output for the life of the
collection. Keying based on mutable properties can result in
unreachable instances "lost" in the collection.
"""
self.keyfunc = keyfunc
self.ignore_unpopulated_attribute = ignore_unpopulated_attribute
super().__init__(*dict_args)
@classmethod
def _unreduce(
cls,
keyfunc: Callable[[Any], Any],
values: Dict[_KT, _KT],
adapter: Optional[CollectionAdapter] = None,
) -> "KeyFuncDict[_KT, _KT]":
mp: KeyFuncDict[_KT, _KT] = KeyFuncDict(keyfunc)
mp.update(values)
# note that the adapter sets itself up onto this collection
# when its `__setstate__` method is called
return mp
def __reduce__(
self,
) -> Tuple[
Callable[[_KT, _KT], KeyFuncDict[_KT, _KT]],
Tuple[Any, Union[Dict[_KT, _KT], Dict[_KT, _KT]], CollectionAdapter],
]:
return (
KeyFuncDict._unreduce,
(
self.keyfunc,
dict(self),
collection_adapter(self),
),
)
@util.preload_module("sqlalchemy.orm.attributes")
def _raise_for_unpopulated(
self,
value: _KT,
initiator: Union[AttributeEventToken, Literal[None, False]] = None,
*,
warn_only: bool,
) -> None:
mapper = base.instance_state(value).mapper
attributes = util.preloaded.orm_attributes
if not isinstance(initiator, attributes.AttributeEventToken):
relationship = "unknown relationship"
elif initiator.key in mapper.attrs:
relationship = f"{mapper.attrs[initiator.key]}"
else:
relationship = initiator.key
if warn_only:
util.warn(
f"Attribute keyed dictionary value for "
f"attribute '{relationship}' was None; this will raise "
"in a future release. "
f"To skip this assignment entirely, "
f'Set the "ignore_unpopulated_attribute=True" '
f"parameter on the mapped collection factory."
)
else:
raise sa_exc.InvalidRequestError(
"In event triggered from population of "
f"attribute '{relationship}' "
"(potentially from a backref), "
f"can't populate value in KeyFuncDict; "
"dictionary key "
f"derived from {base.instance_str(value)} is not "
f"populated. Ensure appropriate state is set up on "
f"the {base.instance_str(value)} object "
f"before assigning to the {relationship} attribute. "
f"To skip this assignment entirely, "
f'Set the "ignore_unpopulated_attribute=True" '
f"parameter on the mapped collection factory."
)
@collection.appender # type: ignore[misc]
@collection.internally_instrumented # type: ignore[misc]
def set(
self,
value: _KT,
_sa_initiator: Union[AttributeEventToken, Literal[None, False]] = None,
) -> None:
"""Add an item by value, consulting the keyfunc for the key."""
key = self.keyfunc(value)
if key is base.NO_VALUE:
if not self.ignore_unpopulated_attribute:
self._raise_for_unpopulated(
value, _sa_initiator, warn_only=False
)
else:
return
elif key is Missing:
if not self.ignore_unpopulated_attribute:
self._raise_for_unpopulated(
value, _sa_initiator, warn_only=True
)
key = None
else:
return
self.__setitem__(key, value, _sa_initiator) # type: ignore[call-arg]
@collection.remover # type: ignore[misc]
@collection.internally_instrumented # type: ignore[misc]
def remove(
self,
value: _KT,
_sa_initiator: Union[AttributeEventToken, Literal[None, False]] = None,
) -> None:
"""Remove an item by value, consulting the keyfunc for the key."""
key = self.keyfunc(value)
if key is base.NO_VALUE:
if not self.ignore_unpopulated_attribute:
self._raise_for_unpopulated(
value, _sa_initiator, warn_only=False
)
return
elif key is Missing:
if not self.ignore_unpopulated_attribute:
self._raise_for_unpopulated(
value, _sa_initiator, warn_only=True
)
key = None
else:
return
# Let self[key] raise if key is not in this collection
# testlib.pragma exempt:__ne__
if self[key] != value:
raise sa_exc.InvalidRequestError(
"Can not remove '%s': collection holds '%s' for key '%s'. "
"Possible cause: is the KeyFuncDict key function "
"based on mutable properties or properties that only obtain "
"values after flush?" % (value, self[key], key)
)
self.__delitem__(key, _sa_initiator) # type: ignore[call-arg]
def _mapped_collection_cls(
keyfunc: Callable[[Any], Any], ignore_unpopulated_attribute: bool
) -> Type[KeyFuncDict[_KT, _KT]]:
class _MKeyfuncMapped(KeyFuncDict[_KT, _KT]):
def __init__(self, *dict_args: Any) -> None:
super().__init__(
keyfunc,
*dict_args,
ignore_unpopulated_attribute=ignore_unpopulated_attribute,
)
return _MKeyfuncMapped
MappedCollection = KeyFuncDict
"""A synonym for :class:`.KeyFuncDict`.
.. versionchanged:: 2.0 Renamed :class:`.MappedCollection` to
:class:`.KeyFuncDict`.
"""
mapped_collection = keyfunc_mapping
"""A synonym for :func:`_orm.keyfunc_mapping`.
.. versionchanged:: 2.0 Renamed :data:`.mapped_collection` to
:func:`_orm.keyfunc_mapping`
"""
attribute_mapped_collection = attribute_keyed_dict
"""A synonym for :func:`_orm.attribute_keyed_dict`.
.. versionchanged:: 2.0 Renamed :data:`.attribute_mapped_collection` to
:func:`_orm.attribute_keyed_dict`
"""
column_mapped_collection = column_keyed_dict
"""A synonym for :func:`_orm.column_keyed_dict.
.. versionchanged:: 2.0 Renamed :func:`.column_mapped_collection` to
:func:`_orm.column_keyed_dict`
"""
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