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venv/lib/python3.11/site-packages/sqlalchemy/orm/dynamic.py
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venv/lib/python3.11/site-packages/sqlalchemy/orm/dynamic.py
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# orm/dynamic.py
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# Copyright (C) 2005-2025 the SQLAlchemy authors and contributors
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# <see AUTHORS file>
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#
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# This module is part of SQLAlchemy and is released under
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# the MIT License: https://www.opensource.org/licenses/mit-license.php
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"""Dynamic collection API.
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Dynamic collections act like Query() objects for read operations and support
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basic add/delete mutation.
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.. legacy:: the "dynamic" loader is a legacy feature, superseded by the
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"write_only" loader.
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"""
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from __future__ import annotations
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from typing import Any
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from typing import Iterable
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from typing import Iterator
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from typing import List
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from typing import Optional
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from typing import Tuple
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from typing import Type
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from typing import TYPE_CHECKING
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from typing import TypeVar
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from typing import Union
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from . import attributes
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from . import exc as orm_exc
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from . import relationships
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from . import util as orm_util
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from .base import PassiveFlag
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from .query import Query
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from .session import object_session
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from .writeonly import AbstractCollectionWriter
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from .writeonly import WriteOnlyAttributeImpl
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from .writeonly import WriteOnlyHistory
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from .writeonly import WriteOnlyLoader
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from .. import util
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from ..engine import result
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if TYPE_CHECKING:
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from . import QueryableAttribute
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from .mapper import Mapper
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from .relationships import _RelationshipOrderByArg
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from .session import Session
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from .state import InstanceState
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from .util import AliasedClass
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from ..event import _Dispatch
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from ..sql.elements import ColumnElement
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_T = TypeVar("_T", bound=Any)
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class DynamicCollectionHistory(WriteOnlyHistory[_T]):
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def __init__(
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self,
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attr: DynamicAttributeImpl,
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state: InstanceState[_T],
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passive: PassiveFlag,
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apply_to: Optional[DynamicCollectionHistory[_T]] = None,
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) -> None:
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if apply_to:
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coll = AppenderQuery(attr, state).autoflush(False)
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self.unchanged_items = util.OrderedIdentitySet(coll)
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self.added_items = apply_to.added_items
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self.deleted_items = apply_to.deleted_items
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self._reconcile_collection = True
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else:
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self.deleted_items = util.OrderedIdentitySet()
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self.added_items = util.OrderedIdentitySet()
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self.unchanged_items = util.OrderedIdentitySet()
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self._reconcile_collection = False
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class DynamicAttributeImpl(WriteOnlyAttributeImpl):
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_supports_dynamic_iteration = True
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collection_history_cls = DynamicCollectionHistory[Any]
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query_class: Type[AppenderMixin[Any]] # type: ignore[assignment]
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def __init__(
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self,
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class_: Union[Type[Any], AliasedClass[Any]],
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key: str,
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dispatch: _Dispatch[QueryableAttribute[Any]],
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target_mapper: Mapper[_T],
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order_by: _RelationshipOrderByArg,
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query_class: Optional[Type[AppenderMixin[_T]]] = None,
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**kw: Any,
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) -> None:
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attributes.AttributeImpl.__init__(
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self, class_, key, None, dispatch, **kw
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)
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self.target_mapper = target_mapper
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if order_by:
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self.order_by = tuple(order_by)
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if not query_class:
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self.query_class = AppenderQuery
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elif AppenderMixin in query_class.mro():
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self.query_class = query_class
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else:
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self.query_class = mixin_user_query(query_class)
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@relationships.RelationshipProperty.strategy_for(lazy="dynamic")
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class DynaLoader(WriteOnlyLoader):
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impl_class = DynamicAttributeImpl
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class AppenderMixin(AbstractCollectionWriter[_T]):
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"""A mixin that expects to be mixing in a Query class with
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AbstractAppender.
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"""
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query_class: Optional[Type[Query[_T]]] = None
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_order_by_clauses: Tuple[ColumnElement[Any], ...]
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def __init__(
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self, attr: DynamicAttributeImpl, state: InstanceState[_T]
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) -> None:
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Query.__init__(
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self, # type: ignore[arg-type]
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attr.target_mapper,
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None,
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)
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super().__init__(attr, state)
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@property
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def session(self) -> Optional[Session]:
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sess = object_session(self.instance)
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if sess is not None and sess.autoflush and self.instance in sess:
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sess.flush()
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if not orm_util.has_identity(self.instance):
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return None
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else:
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return sess
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@session.setter
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def session(self, session: Session) -> None:
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self.sess = session
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def _iter(self) -> Union[result.ScalarResult[_T], result.Result[_T]]:
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sess = self.session
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if sess is None:
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state = attributes.instance_state(self.instance)
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if state.detached:
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util.warn(
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"Instance %s is detached, dynamic relationship cannot "
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"return a correct result. This warning will become "
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"a DetachedInstanceError in a future release."
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% (orm_util.state_str(state))
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)
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return result.IteratorResult(
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result.SimpleResultMetaData([self.attr.class_.__name__]),
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iter(
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self.attr._get_collection_history(
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attributes.instance_state(self.instance),
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PassiveFlag.PASSIVE_NO_INITIALIZE,
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).added_items
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),
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_source_supports_scalars=True,
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).scalars()
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else:
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return self._generate(sess)._iter()
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if TYPE_CHECKING:
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def __iter__(self) -> Iterator[_T]: ...
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def __getitem__(self, index: Any) -> Union[_T, List[_T]]:
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sess = self.session
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if sess is None:
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return self.attr._get_collection_history(
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attributes.instance_state(self.instance),
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PassiveFlag.PASSIVE_NO_INITIALIZE,
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).indexed(index)
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else:
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return self._generate(sess).__getitem__(index) # type: ignore[no-any-return] # noqa: E501
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def count(self) -> int:
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sess = self.session
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if sess is None:
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return len(
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self.attr._get_collection_history(
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attributes.instance_state(self.instance),
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PassiveFlag.PASSIVE_NO_INITIALIZE,
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).added_items
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)
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else:
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return self._generate(sess).count()
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def _generate(
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self,
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sess: Optional[Session] = None,
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) -> Query[_T]:
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# note we're returning an entirely new Query class instance
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# here without any assignment capabilities; the class of this
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# query is determined by the session.
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instance = self.instance
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if sess is None:
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sess = object_session(instance)
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if sess is None:
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raise orm_exc.DetachedInstanceError(
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"Parent instance %s is not bound to a Session, and no "
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"contextual session is established; lazy load operation "
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"of attribute '%s' cannot proceed"
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% (orm_util.instance_str(instance), self.attr.key)
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)
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if self.query_class:
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query = self.query_class(self.attr.target_mapper, session=sess)
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else:
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query = sess.query(self.attr.target_mapper)
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query._where_criteria = self._where_criteria
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query._from_obj = self._from_obj
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query._order_by_clauses = self._order_by_clauses
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return query
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def add_all(self, iterator: Iterable[_T]) -> None:
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"""Add an iterable of items to this :class:`_orm.AppenderQuery`.
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The given items will be persisted to the database in terms of
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the parent instance's collection on the next flush.
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This method is provided to assist in delivering forwards-compatibility
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with the :class:`_orm.WriteOnlyCollection` collection class.
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.. versionadded:: 2.0
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"""
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self._add_all_impl(iterator)
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def add(self, item: _T) -> None:
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"""Add an item to this :class:`_orm.AppenderQuery`.
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The given item will be persisted to the database in terms of
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the parent instance's collection on the next flush.
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This method is provided to assist in delivering forwards-compatibility
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with the :class:`_orm.WriteOnlyCollection` collection class.
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.. versionadded:: 2.0
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"""
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self._add_all_impl([item])
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def extend(self, iterator: Iterable[_T]) -> None:
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"""Add an iterable of items to this :class:`_orm.AppenderQuery`.
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The given items will be persisted to the database in terms of
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the parent instance's collection on the next flush.
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"""
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self._add_all_impl(iterator)
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def append(self, item: _T) -> None:
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"""Append an item to this :class:`_orm.AppenderQuery`.
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The given item will be persisted to the database in terms of
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the parent instance's collection on the next flush.
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"""
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self._add_all_impl([item])
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def remove(self, item: _T) -> None:
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"""Remove an item from this :class:`_orm.AppenderQuery`.
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The given item will be removed from the parent instance's collection on
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the next flush.
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"""
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self._remove_impl(item)
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class AppenderQuery(AppenderMixin[_T], Query[_T]): # type: ignore[misc]
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"""A dynamic query that supports basic collection storage operations.
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Methods on :class:`.AppenderQuery` include all methods of
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:class:`_orm.Query`, plus additional methods used for collection
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persistence.
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"""
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def mixin_user_query(cls: Any) -> type[AppenderMixin[Any]]:
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"""Return a new class with AppenderQuery functionality layered over."""
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name = "Appender" + cls.__name__
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return type(name, (AppenderMixin, cls), {"query_class": cls})
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