JezK
Edit File: relationships.py
# orm/relationships.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 """Heuristics related to join conditions as used in :func:`_orm.relationship`. Provides the :class:`.JoinCondition` object, which encapsulates SQL annotation and aliasing behavior focused on the `primaryjoin` and `secondaryjoin` aspects of :func:`_orm.relationship`. """ from __future__ import absolute_import import collections import re import weakref from . import attributes from .base import _is_mapped_class from .base import PASSIVE_MERGE from .base import state_str from .interfaces import MANYTOMANY from .interfaces import MANYTOONE from .interfaces import ONETOMANY from .interfaces import PropComparator from .interfaces import StrategizedProperty from .util import _orm_annotate from .util import _orm_deannotate from .util import CascadeOptions from .. import exc as sa_exc from .. import log from .. import schema from .. import sql from .. import util from ..inspection import inspect from ..sql import coercions from ..sql import expression from ..sql import operators from ..sql import roles from ..sql import visitors from ..sql.util import _deep_deannotate from ..sql.util import _shallow_annotate from ..sql.util import adapt_criterion_to_null from ..sql.util import ClauseAdapter from ..sql.util import join_condition from ..sql.util import selectables_overlap from ..sql.util import visit_binary_product def remote(expr): """Annotate a portion of a primaryjoin expression with a 'remote' annotation. See the section :ref:`relationship_custom_foreign` for a description of use. .. seealso:: :ref:`relationship_custom_foreign` :func:`.foreign` """ return _annotate_columns( coercions.expect(roles.ColumnArgumentRole, expr), {"remote": True} ) def foreign(expr): """Annotate a portion of a primaryjoin expression with a 'foreign' annotation. See the section :ref:`relationship_custom_foreign` for a description of use. .. seealso:: :ref:`relationship_custom_foreign` :func:`.remote` """ return _annotate_columns( coercions.expect(roles.ColumnArgumentRole, expr), {"foreign": True} ) @log.class_logger class RelationshipProperty(StrategizedProperty): """Describes an object property that holds a single item or list of items that correspond to a related database table. Public constructor is the :func:`_orm.relationship` function. .. seealso:: :ref:`relationship_config_toplevel` """ strategy_wildcard_key = "relationship" inherit_cache = True _links_to_entity = True _persistence_only = dict( passive_deletes=False, passive_updates=True, enable_typechecks=True, active_history=False, cascade_backrefs=True, ) _dependency_processor = None def __init__( self, argument, secondary=None, primaryjoin=None, secondaryjoin=None, foreign_keys=None, uselist=None, order_by=False, backref=None, back_populates=None, overlaps=None, post_update=False, cascade=False, viewonly=False, lazy="select", collection_class=None, passive_deletes=_persistence_only["passive_deletes"], passive_updates=_persistence_only["passive_updates"], remote_side=None, enable_typechecks=_persistence_only["enable_typechecks"], join_depth=None, comparator_factory=None, single_parent=False, innerjoin=False, distinct_target_key=None, doc=None, active_history=_persistence_only["active_history"], cascade_backrefs=_persistence_only["cascade_backrefs"], load_on_pending=False, bake_queries=True, _local_remote_pairs=None, query_class=None, info=None, omit_join=None, sync_backref=None, _legacy_inactive_history_style=False, ): """Provide a relationship between two mapped classes. This corresponds to a parent-child or associative table relationship. The constructed class is an instance of :class:`.RelationshipProperty`. A typical :func:`_orm.relationship`, used in a classical mapping:: mapper(Parent, properties={ 'children': relationship(Child) }) Some arguments accepted by :func:`_orm.relationship` optionally accept a callable function, which when called produces the desired value. The callable is invoked by the parent :class:`_orm.Mapper` at "mapper initialization" time, which happens only when mappers are first used, and is assumed to be after all mappings have been constructed. This can be used to resolve order-of-declaration and other dependency issues, such as if ``Child`` is declared below ``Parent`` in the same file:: mapper(Parent, properties={ "children":relationship(lambda: Child, order_by=lambda: Child.id) }) When using the :ref:`declarative_toplevel` extension, the Declarative initializer allows string arguments to be passed to :func:`_orm.relationship`. These string arguments are converted into callables that evaluate the string as Python code, using the Declarative class-registry as a namespace. This allows the lookup of related classes to be automatic via their string name, and removes the need for related classes to be imported into the local module space before the dependent classes have been declared. It is still required that the modules in which these related classes appear are imported anywhere in the application at some point before the related mappings are actually used, else a lookup error will be raised when the :func:`_orm.relationship` attempts to resolve the string reference to the related class. An example of a string- resolved class is as follows:: from sqlalchemy.ext.declarative import declarative_base Base = declarative_base() class Parent(Base): __tablename__ = 'parent' id = Column(Integer, primary_key=True) children = relationship("Child", order_by="Child.id") .. seealso:: :ref:`relationship_config_toplevel` - Full introductory and reference documentation for :func:`_orm.relationship`. :ref:`tutorial_orm_related_objects` - ORM tutorial introduction. :param argument: A mapped class, or actual :class:`_orm.Mapper` instance, representing the target of the relationship. :paramref:`_orm.relationship.argument` may also be passed as a callable function which is evaluated at mapper initialization time, and may be passed as a string name when using Declarative. .. warning:: Prior to SQLAlchemy 1.3.16, this value is interpreted using Python's ``eval()`` function. **DO NOT PASS UNTRUSTED INPUT TO THIS STRING**. See :ref:`declarative_relationship_eval` for details on declarative evaluation of :func:`_orm.relationship` arguments. .. versionchanged 1.3.16:: The string evaluation of the main "argument" no longer accepts an open ended Python expression, instead only accepting a string class name or dotted package-qualified name. .. seealso:: :ref:`declarative_configuring_relationships` - further detail on relationship configuration when using Declarative. :param secondary: For a many-to-many relationship, specifies the intermediary table, and is typically an instance of :class:`_schema.Table`. In less common circumstances, the argument may also be specified as an :class:`_expression.Alias` construct, or even a :class:`_expression.Join` construct. :paramref:`_orm.relationship.secondary` may also be passed as a callable function which is evaluated at mapper initialization time. When using Declarative, it may also be a string argument noting the name of a :class:`_schema.Table` that is present in the :class:`_schema.MetaData` collection associated with the parent-mapped :class:`_schema.Table`. .. warning:: When passed as a Python-evaluable string, the argument is interpreted using Python's ``eval()`` function. **DO NOT PASS UNTRUSTED INPUT TO THIS STRING**. See :ref:`declarative_relationship_eval` for details on declarative evaluation of :func:`_orm.relationship` arguments. The :paramref:`_orm.relationship.secondary` keyword argument is typically applied in the case where the intermediary :class:`_schema.Table` is not otherwise expressed in any direct class mapping. If the "secondary" table is also explicitly mapped elsewhere (e.g. as in :ref:`association_pattern`), one should consider applying the :paramref:`_orm.relationship.viewonly` flag so that this :func:`_orm.relationship` is not used for persistence operations which may conflict with those of the association object pattern. .. seealso:: :ref:`relationships_many_to_many` - Reference example of "many to many". :ref:`self_referential_many_to_many` - Specifics on using many-to-many in a self-referential case. :ref:`declarative_many_to_many` - Additional options when using Declarative. :ref:`association_pattern` - an alternative to :paramref:`_orm.relationship.secondary` when composing association table relationships, allowing additional attributes to be specified on the association table. :ref:`composite_secondary_join` - a lesser-used pattern which in some cases can enable complex :func:`_orm.relationship` SQL conditions to be used. .. versionadded:: 0.9.2 :paramref:`_orm.relationship.secondary` works more effectively when referring to a :class:`_expression.Join` instance. :param active_history=False: When ``True``, indicates that the "previous" value for a many-to-one reference should be loaded when replaced, if not already loaded. Normally, history tracking logic for simple many-to-ones only needs to be aware of the "new" value in order to perform a flush. This flag is available for applications that make use of :func:`.attributes.get_history` which also need to know the "previous" value of the attribute. :param backref: A reference to a string relationship name, or a :func:`_orm.backref` construct, which will be used to automatically generate a new :func:`_orm.relationship` on the related class, which then refers to this one using a bi-directional :paramref:`_orm.relationship.back_populates` configuration. In modern Python, explicit use of :func:`_orm.relationship` with :paramref:`_orm.relationship.back_populates` should be preferred, as it is more robust in terms of mapper configuration as well as more conceptually straightforward. It also integrates with new :pep:`484` typing features introduced in SQLAlchemy 2.0 which is not possible with dynamically generated attributes. .. seealso:: :ref:`relationships_backref` - notes on using :paramref:`_orm.relationship.backref` :ref:`tutorial_orm_related_objects` - in the :ref:`unified_tutorial`, presents an overview of bi-directional relationship configuration and behaviors using :paramref:`_orm.relationship.back_populates` :func:`.backref` - allows control over :func:`_orm.relationship` configuration when using :paramref:`_orm.relationship.backref`. :param back_populates: Indicates the name of a :func:`_orm.relationship` on the related class that will be synchronized with this one. It is usually expected that the :func:`_orm.relationship` on the related class also refer to this one. This allows objects on both sides of each :func:`_orm.relationship` to synchronize in-Python state changes and also provides directives to the :term:`unit of work` flush process how changes along these relationships should be persisted. .. seealso:: :ref:`tutorial_orm_related_objects` - in the :ref:`unified_tutorial`, presents an overview of bi-directional relationship configuration and behaviors. :ref:`relationship_patterns` - includes many examples of :paramref:`_orm.relationship.back_populates`. :param overlaps: A string name or comma-delimited set of names of other relationships on either this mapper, a descendant mapper, or a target mapper with which this relationship may write to the same foreign keys upon persistence. The only effect this has is to eliminate the warning that this relationship will conflict with another upon persistence. This is used for such relationships that are truly capable of conflicting with each other on write, but the application will ensure that no such conflicts occur. .. versionadded:: 1.4 .. seealso:: :ref:`error_qzyx` - usage example :param bake_queries=True: Legacy parameter, not used. .. versionchanged:: 1.4.23 the "lambda caching" system is no longer used by loader strategies and the ``bake_queries`` parameter has no effect. :param cascade: A comma-separated list of cascade rules which determines how Session operations should be "cascaded" from parent to child. This defaults to ``False``, which means the default cascade should be used - this default cascade is ``"save-update, merge"``. The available cascades are ``save-update``, ``merge``, ``expunge``, ``delete``, ``delete-orphan``, and ``refresh-expire``. An additional option, ``all`` indicates shorthand for ``"save-update, merge, refresh-expire, expunge, delete"``, and is often used as in ``"all, delete-orphan"`` to indicate that related objects should follow along with the parent object in all cases, and be deleted when de-associated. .. seealso:: :ref:`unitofwork_cascades` - Full detail on each of the available cascade options. :param cascade_backrefs=True: A boolean value indicating if the ``save-update`` cascade should operate along an assignment event intercepted by a backref. When set to ``False``, the attribute managed by this relationship will not cascade an incoming transient object into the session of a persistent parent, if the event is received via backref. .. deprecated:: 1.4 The :paramref:`_orm.relationship.cascade_backrefs` flag will default to False in all cases in SQLAlchemy 2.0. .. seealso:: :ref:`backref_cascade` - Full discussion and examples on how the :paramref:`_orm.relationship.cascade_backrefs` option is used. :param collection_class: A class or callable that returns a new list-holding object. will be used in place of a plain list for storing elements. .. seealso:: :ref:`custom_collections` - Introductory documentation and examples. :param comparator_factory: A class which extends :class:`.RelationshipProperty.Comparator` which provides custom SQL clause generation for comparison operations. .. seealso:: :class:`.PropComparator` - some detail on redefining comparators at this level. :ref:`custom_comparators` - Brief intro to this feature. :param distinct_target_key=None: Indicate if a "subquery" eager load should apply the DISTINCT keyword to the innermost SELECT statement. When left as ``None``, the DISTINCT keyword will be applied in those cases when the target columns do not comprise the full primary key of the target table. When set to ``True``, the DISTINCT keyword is applied to the innermost SELECT unconditionally. It may be desirable to set this flag to False when the DISTINCT is reducing performance of the innermost subquery beyond that of what duplicate innermost rows may be causing. .. versionchanged:: 0.9.0 - :paramref:`_orm.relationship.distinct_target_key` now defaults to ``None``, so that the feature enables itself automatically for those cases where the innermost query targets a non-unique key. .. seealso:: :ref:`loading_toplevel` - includes an introduction to subquery eager loading. :param doc: Docstring which will be applied to the resulting descriptor. :param foreign_keys: A list of columns which are to be used as "foreign key" columns, or columns which refer to the value in a remote column, within the context of this :func:`_orm.relationship` object's :paramref:`_orm.relationship.primaryjoin` condition. That is, if the :paramref:`_orm.relationship.primaryjoin` condition of this :func:`_orm.relationship` is ``a.id == b.a_id``, and the values in ``b.a_id`` are required to be present in ``a.id``, then the "foreign key" column of this :func:`_orm.relationship` is ``b.a_id``. In normal cases, the :paramref:`_orm.relationship.foreign_keys` parameter is **not required.** :func:`_orm.relationship` will automatically determine which columns in the :paramref:`_orm.relationship.primaryjoin` condition are to be considered "foreign key" columns based on those :class:`_schema.Column` objects that specify :class:`_schema.ForeignKey`, or are otherwise listed as referencing columns in a :class:`_schema.ForeignKeyConstraint` construct. :paramref:`_orm.relationship.foreign_keys` is only needed when: 1. There is more than one way to construct a join from the local table to the remote table, as there are multiple foreign key references present. Setting ``foreign_keys`` will limit the :func:`_orm.relationship` to consider just those columns specified here as "foreign". 2. The :class:`_schema.Table` being mapped does not actually have :class:`_schema.ForeignKey` or :class:`_schema.ForeignKeyConstraint` constructs present, often because the table was reflected from a database that does not support foreign key reflection (MySQL MyISAM). 3. The :paramref:`_orm.relationship.primaryjoin` argument is used to construct a non-standard join condition, which makes use of columns or expressions that do not normally refer to their "parent" column, such as a join condition expressed by a complex comparison using a SQL function. The :func:`_orm.relationship` construct will raise informative error messages that suggest the use of the :paramref:`_orm.relationship.foreign_keys` parameter when presented with an ambiguous condition. In typical cases, if :func:`_orm.relationship` doesn't raise any exceptions, the :paramref:`_orm.relationship.foreign_keys` parameter is usually not needed. :paramref:`_orm.relationship.foreign_keys` may also be passed as a callable function which is evaluated at mapper initialization time, and may be passed as a Python-evaluable string when using Declarative. .. warning:: When passed as a Python-evaluable string, the argument is interpreted using Python's ``eval()`` function. **DO NOT PASS UNTRUSTED INPUT TO THIS STRING**. See :ref:`declarative_relationship_eval` for details on declarative evaluation of :func:`_orm.relationship` arguments. .. seealso:: :ref:`relationship_foreign_keys` :ref:`relationship_custom_foreign` :func:`.foreign` - allows direct annotation of the "foreign" columns within a :paramref:`_orm.relationship.primaryjoin` condition. :param info: Optional data dictionary which will be populated into the :attr:`.MapperProperty.info` attribute of this object. :param innerjoin=False: When ``True``, joined eager loads will use an inner join to join against related tables instead of an outer join. The purpose of this option is generally one of performance, as inner joins generally perform better than outer joins. This flag can be set to ``True`` when the relationship references an object via many-to-one using local foreign keys that are not nullable, or when the reference is one-to-one or a collection that is guaranteed to have one or at least one entry. The option supports the same "nested" and "unnested" options as that of :paramref:`_orm.joinedload.innerjoin`. See that flag for details on nested / unnested behaviors. .. seealso:: :paramref:`_orm.joinedload.innerjoin` - the option as specified by loader option, including detail on nesting behavior. :ref:`what_kind_of_loading` - Discussion of some details of various loader options. :param join_depth: When non-``None``, an integer value indicating how many levels deep "eager" loaders should join on a self-referring or cyclical relationship. The number counts how many times the same Mapper shall be present in the loading condition along a particular join branch. When left at its default of ``None``, eager loaders will stop chaining when they encounter a the same target mapper which is already higher up in the chain. This option applies both to joined- and subquery- eager loaders. .. seealso:: :ref:`self_referential_eager_loading` - Introductory documentation and examples. :param lazy='select': specifies How the related items should be loaded. Default value is ``select``. Values include: * ``select`` - items should be loaded lazily when the property is first accessed, using a separate SELECT statement, or identity map fetch for simple many-to-one references. * ``immediate`` - items should be loaded as the parents are loaded, using a separate SELECT statement, or identity map fetch for simple many-to-one references. * ``joined`` - items should be loaded "eagerly" in the same query as that of the parent, using a JOIN or LEFT OUTER JOIN. Whether the join is "outer" or not is determined by the :paramref:`_orm.relationship.innerjoin` parameter. * ``subquery`` - items should be loaded "eagerly" as the parents are loaded, using one additional SQL statement, which issues a JOIN to a subquery of the original statement, for each collection requested. * ``selectin`` - items should be loaded "eagerly" as the parents are loaded, using one or more additional SQL statements, which issues a JOIN to the immediate parent object, specifying primary key identifiers using an IN clause. .. versionadded:: 1.2 * ``noload`` - no loading should occur at any time. This is to support "write-only" attributes, or attributes which are populated in some manner specific to the application. * ``raise`` - lazy loading is disallowed; accessing the attribute, if its value were not already loaded via eager loading, will raise an :exc:`~sqlalchemy.exc.InvalidRequestError`. This strategy can be used when objects are to be detached from their attached :class:`.Session` after they are loaded. .. versionadded:: 1.1 * ``raise_on_sql`` - lazy loading that emits SQL is disallowed; accessing the attribute, if its value were not already loaded via eager loading, will raise an :exc:`~sqlalchemy.exc.InvalidRequestError`, **if the lazy load needs to emit SQL**. If the lazy load can pull the related value from the identity map or determine that it should be None, the value is loaded. This strategy can be used when objects will remain associated with the attached :class:`.Session`, however additional SELECT statements should be blocked. .. versionadded:: 1.1 * ``dynamic`` - the attribute will return a pre-configured :class:`_query.Query` object for all read operations, onto which further filtering operations can be applied before iterating the results. See the section :ref:`dynamic_relationship` for more details. * True - a synonym for 'select' * False - a synonym for 'joined' * None - a synonym for 'noload' .. seealso:: :doc:`/orm/loading_relationships` - Full documentation on relationship loader configuration. :ref:`dynamic_relationship` - detail on the ``dynamic`` option. :ref:`collections_noload_raiseload` - notes on "noload" and "raise" :param load_on_pending=False: Indicates loading behavior for transient or pending parent objects. When set to ``True``, causes the lazy-loader to issue a query for a parent object that is not persistent, meaning it has never been flushed. This may take effect for a pending object when autoflush is disabled, or for a transient object that has been "attached" to a :class:`.Session` but is not part of its pending collection. The :paramref:`_orm.relationship.load_on_pending` flag does not improve behavior when the ORM is used normally - object references should be constructed at the object level, not at the foreign key level, so that they are present in an ordinary way before a flush proceeds. This flag is not not intended for general use. .. seealso:: :meth:`.Session.enable_relationship_loading` - this method establishes "load on pending" behavior for the whole object, and also allows loading on objects that remain transient or detached. :param order_by: Indicates the ordering that should be applied when loading these items. :paramref:`_orm.relationship.order_by` is expected to refer to one of the :class:`_schema.Column` objects to which the target class is mapped, or the attribute itself bound to the target class which refers to the column. :paramref:`_orm.relationship.order_by` may also be passed as a callable function which is evaluated at mapper initialization time, and may be passed as a Python-evaluable string when using Declarative. .. warning:: When passed as a Python-evaluable string, the argument is interpreted using Python's ``eval()`` function. **DO NOT PASS UNTRUSTED INPUT TO THIS STRING**. See :ref:`declarative_relationship_eval` for details on declarative evaluation of :func:`_orm.relationship` arguments. :param passive_deletes=False: Indicates loading behavior during delete operations. A value of True indicates that unloaded child items should not be loaded during a delete operation on the parent. Normally, when a parent item is deleted, all child items are loaded so that they can either be marked as deleted, or have their foreign key to the parent set to NULL. Marking this flag as True usually implies an ON DELETE <CASCADE|SET NULL> rule is in place which will handle updating/deleting child rows on the database side. Additionally, setting the flag to the string value 'all' will disable the "nulling out" of the child foreign keys, when the parent object is deleted and there is no delete or delete-orphan cascade enabled. This is typically used when a triggering or error raise scenario is in place on the database side. Note that the foreign key attributes on in-session child objects will not be changed after a flush occurs so this is a very special use-case setting. Additionally, the "nulling out" will still occur if the child object is de-associated with the parent. .. seealso:: :ref:`passive_deletes` - Introductory documentation and examples. :param passive_updates=True: Indicates the persistence behavior to take when a referenced primary key value changes in place, indicating that the referencing foreign key columns will also need their value changed. When True, it is assumed that ``ON UPDATE CASCADE`` is configured on the foreign key in the database, and that the database will handle propagation of an UPDATE from a source column to dependent rows. When False, the SQLAlchemy :func:`_orm.relationship` construct will attempt to emit its own UPDATE statements to modify related targets. However note that SQLAlchemy **cannot** emit an UPDATE for more than one level of cascade. Also, setting this flag to False is not compatible in the case where the database is in fact enforcing referential integrity, unless those constraints are explicitly "deferred", if the target backend supports it. It is highly advised that an application which is employing mutable primary keys keeps ``passive_updates`` set to True, and instead uses the referential integrity features of the database itself in order to handle the change efficiently and fully. .. seealso:: :ref:`passive_updates` - Introductory documentation and examples. :paramref:`.mapper.passive_updates` - a similar flag which takes effect for joined-table inheritance mappings. :param post_update: This indicates that the relationship should be handled by a second UPDATE statement after an INSERT or before a DELETE. Currently, it also will issue an UPDATE after the instance was UPDATEd as well, although this technically should be improved. This flag is used to handle saving bi-directional dependencies between two individual rows (i.e. each row references the other), where it would otherwise be impossible to INSERT or DELETE both rows fully since one row exists before the other. Use this flag when a particular mapping arrangement will incur two rows that are dependent on each other, such as a table that has a one-to-many relationship to a set of child rows, and also has a column that references a single child row within that list (i.e. both tables contain a foreign key to each other). If a flush operation returns an error that a "cyclical dependency" was detected, this is a cue that you might want to use :paramref:`_orm.relationship.post_update` to "break" the cycle. .. seealso:: :ref:`post_update` - Introductory documentation and examples. :param primaryjoin: A SQL expression that will be used as the primary join of the child object against the parent object, or in a many-to-many relationship the join of the parent object to the association table. By default, this value is computed based on the foreign key relationships of the parent and child tables (or association table). :paramref:`_orm.relationship.primaryjoin` may also be passed as a callable function which is evaluated at mapper initialization time, and may be passed as a Python-evaluable string when using Declarative. .. warning:: When passed as a Python-evaluable string, the argument is interpreted using Python's ``eval()`` function. **DO NOT PASS UNTRUSTED INPUT TO THIS STRING**. See :ref:`declarative_relationship_eval` for details on declarative evaluation of :func:`_orm.relationship` arguments. .. seealso:: :ref:`relationship_primaryjoin` :param remote_side: Used for self-referential relationships, indicates the column or list of columns that form the "remote side" of the relationship. :paramref:`_orm.relationship.remote_side` may also be passed as a callable function which is evaluated at mapper initialization time, and may be passed as a Python-evaluable string when using Declarative. .. warning:: When passed as a Python-evaluable string, the argument is interpreted using Python's ``eval()`` function. **DO NOT PASS UNTRUSTED INPUT TO THIS STRING**. See :ref:`declarative_relationship_eval` for details on declarative evaluation of :func:`_orm.relationship` arguments. .. seealso:: :ref:`self_referential` - in-depth explanation of how :paramref:`_orm.relationship.remote_side` is used to configure self-referential relationships. :func:`.remote` - an annotation function that accomplishes the same purpose as :paramref:`_orm.relationship.remote_side`, typically when a custom :paramref:`_orm.relationship.primaryjoin` condition is used. :param query_class: A :class:`_query.Query` subclass that will be used internally by the ``AppenderQuery`` returned by a "dynamic" relationship, that is, a relationship that specifies ``lazy="dynamic"`` or was otherwise constructed using the :func:`_orm.dynamic_loader` function. .. seealso:: :ref:`dynamic_relationship` - Introduction to "dynamic" relationship loaders. :param secondaryjoin: A SQL expression that will be used as the join of an association table to the child object. By default, this value is computed based on the foreign key relationships of the association and child tables. :paramref:`_orm.relationship.secondaryjoin` may also be passed as a callable function which is evaluated at mapper initialization time, and may be passed as a Python-evaluable string when using Declarative. .. warning:: When passed as a Python-evaluable string, the argument is interpreted using Python's ``eval()`` function. **DO NOT PASS UNTRUSTED INPUT TO THIS STRING**. See :ref:`declarative_relationship_eval` for details on declarative evaluation of :func:`_orm.relationship` arguments. .. seealso:: :ref:`relationship_primaryjoin` :param single_parent: When True, installs a validator which will prevent objects from being associated with more than one parent at a time. This is used for many-to-one or many-to-many relationships that should be treated either as one-to-one or one-to-many. Its usage is optional, except for :func:`_orm.relationship` constructs which are many-to-one or many-to-many and also specify the ``delete-orphan`` cascade option. The :func:`_orm.relationship` construct itself will raise an error instructing when this option is required. .. seealso:: :ref:`unitofwork_cascades` - includes detail on when the :paramref:`_orm.relationship.single_parent` flag may be appropriate. :param uselist: A boolean that indicates if this property should be loaded as a list or a scalar. In most cases, this value is determined automatically by :func:`_orm.relationship` at mapper configuration time, based on the type and direction of the relationship - one to many forms a list, many to one forms a scalar, many to many is a list. If a scalar is desired where normally a list would be present, such as a bi-directional one-to-one relationship, set :paramref:`_orm.relationship.uselist` to False. The :paramref:`_orm.relationship.uselist` flag is also available on an existing :func:`_orm.relationship` construct as a read-only attribute, which can be used to determine if this :func:`_orm.relationship` deals with collections or scalar attributes:: >>> User.addresses.property.uselist True .. seealso:: :ref:`relationships_one_to_one` - Introduction to the "one to one" relationship pattern, which is typically when the :paramref:`_orm.relationship.uselist` flag is needed. :param viewonly=False: When set to ``True``, the relationship is used only for loading objects, and not for any persistence operation. A :func:`_orm.relationship` which specifies :paramref:`_orm.relationship.viewonly` can work with a wider range of SQL operations within the :paramref:`_orm.relationship.primaryjoin` condition, including operations that feature the use of a variety of comparison operators as well as SQL functions such as :func:`_expression.cast`. The :paramref:`_orm.relationship.viewonly` flag is also of general use when defining any kind of :func:`_orm.relationship` that doesn't represent the full set of related objects, to prevent modifications of the collection from resulting in persistence operations. When using the :paramref:`_orm.relationship.viewonly` flag in conjunction with backrefs, the originating relationship for a particular state change will not produce state changes within the viewonly relationship. This is the behavior implied by :paramref:`_orm.relationship.sync_backref` being set to False. .. versionchanged:: 1.3.17 - the :paramref:`_orm.relationship.sync_backref` flag is set to False when using viewonly in conjunction with backrefs. .. seealso:: :paramref:`_orm.relationship.sync_backref` :param sync_backref: A boolean that enables the events used to synchronize the in-Python attributes when this relationship is target of either :paramref:`_orm.relationship.backref` or :paramref:`_orm.relationship.back_populates`. Defaults to ``None``, which indicates that an automatic value should be selected based on the value of the :paramref:`_orm.relationship.viewonly` flag. When left at its default, changes in state will be back-populated only if neither sides of a relationship is viewonly. .. versionadded:: 1.3.17 .. versionchanged:: 1.4 - A relationship that specifies :paramref:`_orm.relationship.viewonly` automatically implies that :paramref:`_orm.relationship.sync_backref` is ``False``. .. seealso:: :paramref:`_orm.relationship.viewonly` :param omit_join: Allows manual control over the "selectin" automatic join optimization. Set to ``False`` to disable the "omit join" feature added in SQLAlchemy 1.3; or leave as ``None`` to leave automatic optimization in place. .. note:: This flag may only be set to ``False``. It is not necessary to set it to ``True`` as the "omit_join" optimization is automatically detected; if it is not detected, then the optimization is not supported. .. versionchanged:: 1.3.11 setting ``omit_join`` to True will now emit a warning as this was not the intended use of this flag. .. versionadded:: 1.3 """ super(RelationshipProperty, self).__init__() self.uselist = uselist self.argument = argument self.secondary = secondary self.primaryjoin = primaryjoin self.secondaryjoin = secondaryjoin self.post_update = post_update self.direction = None self.viewonly = viewonly if viewonly: self._warn_for_persistence_only_flags( passive_deletes=passive_deletes, passive_updates=passive_updates, enable_typechecks=enable_typechecks, active_history=active_history, cascade_backrefs=cascade_backrefs, ) if viewonly and sync_backref: raise sa_exc.ArgumentError( "sync_backref and viewonly cannot both be True" ) self.sync_backref = sync_backref self.lazy = lazy self.single_parent = single_parent self._user_defined_foreign_keys = foreign_keys self.collection_class = collection_class self.passive_deletes = passive_deletes self.cascade_backrefs = cascade_backrefs self.passive_updates = passive_updates self.remote_side = remote_side self.enable_typechecks = enable_typechecks self.query_class = query_class self.innerjoin = innerjoin self.distinct_target_key = distinct_target_key self.doc = doc self.active_history = active_history self._legacy_inactive_history_style = _legacy_inactive_history_style self.join_depth = join_depth if omit_join: util.warn( "setting omit_join to True is not supported; selectin " "loading of this relationship may not work correctly if this " "flag is set explicitly. omit_join optimization is " "automatically detected for conditions under which it is " "supported." ) self.omit_join = omit_join self.local_remote_pairs = _local_remote_pairs self.bake_queries = bake_queries self.load_on_pending = load_on_pending self.comparator_factory = ( comparator_factory or RelationshipProperty.Comparator ) self.comparator = self.comparator_factory(self, None) util.set_creation_order(self) if info is not None: self.info = info self.strategy_key = (("lazy", self.lazy),) self._reverse_property = set() if overlaps: self._overlaps = set(re.split(r"\s*,\s*", overlaps)) else: self._overlaps = () if cascade is not False: self.cascade = cascade elif self.viewonly: self.cascade = "merge" else: self.cascade = "save-update, merge" self.order_by = order_by self.back_populates = back_populates if self.back_populates: if backref: raise sa_exc.ArgumentError( "backref and back_populates keyword arguments " "are mutually exclusive" ) self.backref = None else: self.backref = backref def _warn_for_persistence_only_flags(self, **kw): for k, v in kw.items(): if v != self._persistence_only[k]: # we are warning here rather than warn deprecated as this is a # configuration mistake, and Python shows regular warnings more # aggressively than deprecation warnings by default. Unlike the # case of setting viewonly with cascade, the settings being # warned about here are not actively doing the wrong thing # against viewonly=True, so it is not as urgent to have these # raise an error. util.warn( "Setting %s on relationship() while also " "setting viewonly=True does not make sense, as a " "viewonly=True relationship does not perform persistence " "operations. This configuration may raise an error " "in a future release." % (k,) ) def instrument_class(self, mapper): attributes.register_descriptor( mapper.class_, self.key, comparator=self.comparator_factory(self, mapper), parententity=mapper, doc=self.doc, ) class Comparator(PropComparator): """Produce boolean, comparison, and other operators for :class:`.RelationshipProperty` attributes. See the documentation for :class:`.PropComparator` for a brief overview of ORM level operator definition. .. seealso:: :class:`.PropComparator` :class:`.ColumnProperty.Comparator` :class:`.ColumnOperators` :ref:`types_operators` :attr:`.TypeEngine.comparator_factory` """ _of_type = None _extra_criteria = () def __init__( self, prop, parentmapper, adapt_to_entity=None, of_type=None, extra_criteria=(), ): """Construction of :class:`.RelationshipProperty.Comparator` is internal to the ORM's attribute mechanics. """ self.prop = prop self._parententity = parentmapper self._adapt_to_entity = adapt_to_entity if of_type: self._of_type = of_type self._extra_criteria = extra_criteria def adapt_to_entity(self, adapt_to_entity): return self.__class__( self.property, self._parententity, adapt_to_entity=adapt_to_entity, of_type=self._of_type, ) @util.memoized_property def entity(self): """The target entity referred to by this :class:`.RelationshipProperty.Comparator`. This is either a :class:`_orm.Mapper` or :class:`.AliasedInsp` object. This is the "target" or "remote" side of the :func:`_orm.relationship`. """ # this is a relatively recent change made for # 1.4.27 as part of #7244. # TODO: shouldn't _of_type be inspected up front when received? if self._of_type is not None: return inspect(self._of_type) else: return self.property.entity @util.memoized_property def mapper(self): """The target :class:`_orm.Mapper` referred to by this :class:`.RelationshipProperty.Comparator`. This is the "target" or "remote" side of the :func:`_orm.relationship`. """ return self.property.mapper @util.memoized_property def _parententity(self): return self.property.parent def _source_selectable(self): if self._adapt_to_entity: return self._adapt_to_entity.selectable else: return self.property.parent._with_polymorphic_selectable def __clause_element__(self): adapt_from = self._source_selectable() if self._of_type: of_type_entity = inspect(self._of_type) else: of_type_entity = None ( pj, sj, source, dest, secondary, target_adapter, ) = self.property._create_joins( source_selectable=adapt_from, source_polymorphic=True, of_type_entity=of_type_entity, alias_secondary=True, extra_criteria=self._extra_criteria, ) if sj is not None: return pj & sj else: return pj def of_type(self, cls): r"""Redefine this object in terms of a polymorphic subclass. See :meth:`.PropComparator.of_type` for an example. """ return RelationshipProperty.Comparator( self.property, self._parententity, adapt_to_entity=self._adapt_to_entity, of_type=cls, extra_criteria=self._extra_criteria, ) def and_(self, *other): """Add AND criteria. See :meth:`.PropComparator.and_` for an example. .. versionadded:: 1.4 """ return RelationshipProperty.Comparator( self.property, self._parententity, adapt_to_entity=self._adapt_to_entity, of_type=self._of_type, extra_criteria=self._extra_criteria + other, ) def in_(self, other): """Produce an IN clause - this is not implemented for :func:`_orm.relationship`-based attributes at this time. """ raise NotImplementedError( "in_() not yet supported for " "relationships. For a simple " "many-to-one, use in_() against " "the set of foreign key values." ) __hash__ = None def __eq__(self, other): """Implement the ``==`` operator. In a many-to-one context, such as:: MyClass.some_prop == <some object> this will typically produce a clause such as:: mytable.related_id == <some id> Where ``<some id>`` is the primary key of the given object. The ``==`` operator provides partial functionality for non- many-to-one comparisons: * Comparisons against collections are not supported. Use :meth:`~.RelationshipProperty.Comparator.contains`. * Compared to a scalar one-to-many, will produce a clause that compares the target columns in the parent to the given target. * Compared to a scalar many-to-many, an alias of the association table will be rendered as well, forming a natural join that is part of the main body of the query. This will not work for queries that go beyond simple AND conjunctions of comparisons, such as those which use OR. Use explicit joins, outerjoins, or :meth:`~.RelationshipProperty.Comparator.has` for more comprehensive non-many-to-one scalar membership tests. * Comparisons against ``None`` given in a one-to-many or many-to-many context produce a NOT EXISTS clause. """ if isinstance(other, (util.NoneType, expression.Null)): if self.property.direction in [ONETOMANY, MANYTOMANY]: return ~self._criterion_exists() else: return _orm_annotate( self.property._optimized_compare( None, adapt_source=self.adapter ) ) elif self.property.uselist: raise sa_exc.InvalidRequestError( "Can't compare a collection to an object or collection; " "use contains() to test for membership." ) else: return _orm_annotate( self.property._optimized_compare( other, adapt_source=self.adapter ) ) def _criterion_exists(self, criterion=None, **kwargs): if getattr(self, "_of_type", None): info = inspect(self._of_type) target_mapper, to_selectable, is_aliased_class = ( info.mapper, info.selectable, info.is_aliased_class, ) if self.property._is_self_referential and not is_aliased_class: to_selectable = to_selectable._anonymous_fromclause() single_crit = target_mapper._single_table_criterion if single_crit is not None: if criterion is not None: criterion = single_crit & criterion else: criterion = single_crit else: is_aliased_class = False to_selectable = None if self.adapter: source_selectable = self._source_selectable() else: source_selectable = None ( pj, sj, source, dest, secondary, target_adapter, ) = self.property._create_joins( dest_selectable=to_selectable, source_selectable=source_selectable, ) for k in kwargs: crit = getattr(self.property.mapper.class_, k) == kwargs[k] if criterion is None: criterion = crit else: criterion = criterion & crit # annotate the *local* side of the join condition, in the case # of pj + sj this is the full primaryjoin, in the case of just # pj its the local side of the primaryjoin. if sj is not None: j = _orm_annotate(pj) & sj else: j = _orm_annotate(pj, exclude=self.property.remote_side) if ( criterion is not None and target_adapter and not is_aliased_class ): # limit this adapter to annotated only? criterion = target_adapter.traverse(criterion) # only have the "joined left side" of what we # return be subject to Query adaption. The right # side of it is used for an exists() subquery and # should not correlate or otherwise reach out # to anything in the enclosing query. if criterion is not None: criterion = criterion._annotate( {"no_replacement_traverse": True} ) crit = j & sql.True_._ifnone(criterion) if secondary is not None: ex = ( sql.exists(1) .where(crit) .select_from(dest, secondary) .correlate_except(dest, secondary) ) else: ex = ( sql.exists(1) .where(crit) .select_from(dest) .correlate_except(dest) ) return ex def any(self, criterion=None, **kwargs): """Produce an expression that tests a collection against particular criterion, using EXISTS. An expression like:: session.query(MyClass).filter( MyClass.somereference.any(SomeRelated.x==2) ) Will produce a query like:: SELECT * FROM my_table WHERE EXISTS (SELECT 1 FROM related WHERE related.my_id=my_table.id AND related.x=2) Because :meth:`~.RelationshipProperty.Comparator.any` uses a correlated subquery, its performance is not nearly as good when compared against large target tables as that of using a join. :meth:`~.RelationshipProperty.Comparator.any` is particularly useful for testing for empty collections:: session.query(MyClass).filter( ~MyClass.somereference.any() ) will produce:: SELECT * FROM my_table WHERE NOT (EXISTS (SELECT 1 FROM related WHERE related.my_id=my_table.id)) :meth:`~.RelationshipProperty.Comparator.any` is only valid for collections, i.e. a :func:`_orm.relationship` that has ``uselist=True``. For scalar references, use :meth:`~.RelationshipProperty.Comparator.has`. """ if not self.property.uselist: raise sa_exc.InvalidRequestError( "'any()' not implemented for scalar " "attributes. Use has()." ) return self._criterion_exists(criterion, **kwargs) def has(self, criterion=None, **kwargs): """Produce an expression that tests a scalar reference against particular criterion, using EXISTS. An expression like:: session.query(MyClass).filter( MyClass.somereference.has(SomeRelated.x==2) ) Will produce a query like:: SELECT * FROM my_table WHERE EXISTS (SELECT 1 FROM related WHERE related.id==my_table.related_id AND related.x=2) Because :meth:`~.RelationshipProperty.Comparator.has` uses a correlated subquery, its performance is not nearly as good when compared against large target tables as that of using a join. :meth:`~.RelationshipProperty.Comparator.has` is only valid for scalar references, i.e. a :func:`_orm.relationship` that has ``uselist=False``. For collection references, use :meth:`~.RelationshipProperty.Comparator.any`. """ if self.property.uselist: raise sa_exc.InvalidRequestError( "'has()' not implemented for collections. " "Use any()." ) return self._criterion_exists(criterion, **kwargs) def contains(self, other, **kwargs): """Return a simple expression that tests a collection for containment of a particular item. :meth:`~.RelationshipProperty.Comparator.contains` is only valid for a collection, i.e. a :func:`_orm.relationship` that implements one-to-many or many-to-many with ``uselist=True``. When used in a simple one-to-many context, an expression like:: MyClass.contains(other) Produces a clause like:: mytable.id == <some id> Where ``<some id>`` is the value of the foreign key attribute on ``other`` which refers to the primary key of its parent object. From this it follows that :meth:`~.RelationshipProperty.Comparator.contains` is very useful when used with simple one-to-many operations. For many-to-many operations, the behavior of :meth:`~.RelationshipProperty.Comparator.contains` has more caveats. The association table will be rendered in the statement, producing an "implicit" join, that is, includes multiple tables in the FROM clause which are equated in the WHERE clause:: query(MyClass).filter(MyClass.contains(other)) Produces a query like:: SELECT * FROM my_table, my_association_table AS my_association_table_1 WHERE my_table.id = my_association_table_1.parent_id AND my_association_table_1.child_id = <some id> Where ``<some id>`` would be the primary key of ``other``. From the above, it is clear that :meth:`~.RelationshipProperty.Comparator.contains` will **not** work with many-to-many collections when used in queries that move beyond simple AND conjunctions, such as multiple :meth:`~.RelationshipProperty.Comparator.contains` expressions joined by OR. In such cases subqueries or explicit "outer joins" will need to be used instead. See :meth:`~.RelationshipProperty.Comparator.any` for a less-performant alternative using EXISTS, or refer to :meth:`_query.Query.outerjoin` as well as :ref:`orm_queryguide_joins` for more details on constructing outer joins. kwargs may be ignored by this operator but are required for API conformance. """ if not self.property.uselist: raise sa_exc.InvalidRequestError( "'contains' not implemented for scalar " "attributes. Use ==" ) clause = self.property._optimized_compare( other, adapt_source=self.adapter ) if self.property.secondaryjoin is not None: clause.negation_clause = self.__negated_contains_or_equals( other ) return clause def __negated_contains_or_equals(self, other): if self.property.direction == MANYTOONE: state = attributes.instance_state(other) def state_bindparam(local_col, state, remote_col): dict_ = state.dict return sql.bindparam( local_col.key, type_=local_col.type, unique=True, callable_=self.property._get_attr_w_warn_on_none( self.property.mapper, state, dict_, remote_col ), ) def adapt(col): if self.adapter: return self.adapter(col) else: return col if self.property._use_get: return sql.and_( *[ sql.or_( adapt(x) != state_bindparam(adapt(x), state, y), adapt(x) == None, ) for (x, y) in self.property.local_remote_pairs ] ) criterion = sql.and_( *[ x == y for (x, y) in zip( self.property.mapper.primary_key, self.property.mapper.primary_key_from_instance(other), ) ] ) return ~self._criterion_exists(criterion) def __ne__(self, other): """Implement the ``!=`` operator. In a many-to-one context, such as:: MyClass.some_prop != <some object> This will typically produce a clause such as:: mytable.related_id != <some id> Where ``<some id>`` is the primary key of the given object. The ``!=`` operator provides partial functionality for non- many-to-one comparisons: * Comparisons against collections are not supported. Use :meth:`~.RelationshipProperty.Comparator.contains` in conjunction with :func:`_expression.not_`. * Compared to a scalar one-to-many, will produce a clause that compares the target columns in the parent to the given target. * Compared to a scalar many-to-many, an alias of the association table will be rendered as well, forming a natural join that is part of the main body of the query. This will not work for queries that go beyond simple AND conjunctions of comparisons, such as those which use OR. Use explicit joins, outerjoins, or :meth:`~.RelationshipProperty.Comparator.has` in conjunction with :func:`_expression.not_` for more comprehensive non-many-to-one scalar membership tests. * Comparisons against ``None`` given in a one-to-many or many-to-many context produce an EXISTS clause. """ if isinstance(other, (util.NoneType, expression.Null)): if self.property.direction == MANYTOONE: return _orm_annotate( ~self.property._optimized_compare( None, adapt_source=self.adapter ) ) else: return self._criterion_exists() elif self.property.uselist: raise sa_exc.InvalidRequestError( "Can't compare a collection" " to an object or collection; use " "contains() to test for membership." ) else: return _orm_annotate(self.__negated_contains_or_equals(other)) @util.memoized_property def property(self): self.prop.parent._check_configure() return self.prop def _with_parent(self, instance, alias_secondary=True, from_entity=None): assert instance is not None adapt_source = None if from_entity is not None: insp = inspect(from_entity) if insp.is_aliased_class: adapt_source = insp._adapter.adapt_clause return self._optimized_compare( instance, value_is_parent=True, adapt_source=adapt_source, alias_secondary=alias_secondary, ) def _optimized_compare( self, state, value_is_parent=False, adapt_source=None, alias_secondary=True, ): if state is not None: try: state = inspect(state) except sa_exc.NoInspectionAvailable: state = None if state is None or not getattr(state, "is_instance", False): raise sa_exc.ArgumentError( "Mapped instance expected for relationship " "comparison to object. Classes, queries and other " "SQL elements are not accepted in this context; for " "comparison with a subquery, " "use %s.has(**criteria)." % self ) reverse_direction = not value_is_parent if state is None: return self._lazy_none_clause( reverse_direction, adapt_source=adapt_source ) if not reverse_direction: criterion, bind_to_col = ( self._lazy_strategy._lazywhere, self._lazy_strategy._bind_to_col, ) else: criterion, bind_to_col = ( self._lazy_strategy._rev_lazywhere, self._lazy_strategy._rev_bind_to_col, ) if reverse_direction: mapper = self.mapper else: mapper = self.parent dict_ = attributes.instance_dict(state.obj()) def visit_bindparam(bindparam): if bindparam._identifying_key in bind_to_col: bindparam.callable = self._get_attr_w_warn_on_none( mapper, state, dict_, bind_to_col[bindparam._identifying_key], ) if self.secondary is not None and alias_secondary: criterion = ClauseAdapter( self.secondary._anonymous_fromclause() ).traverse(criterion) criterion = visitors.cloned_traverse( criterion, {}, {"bindparam": visit_bindparam} ) if adapt_source: criterion = adapt_source(criterion) return criterion def _get_attr_w_warn_on_none(self, mapper, state, dict_, column): """Create the callable that is used in a many-to-one expression. E.g.:: u1 = s.query(User).get(5) expr = Address.user == u1 Above, the SQL should be "address.user_id = 5". The callable returned by this method produces the value "5" based on the identity of ``u1``. """ # in this callable, we're trying to thread the needle through # a wide variety of scenarios, including: # # * the object hasn't been flushed yet and there's no value for # the attribute as of yet # # * the object hasn't been flushed yet but it has a user-defined # value # # * the object has a value but it's expired and not locally present # # * the object has a value but it's expired and not locally present, # and the object is also detached # # * The object hadn't been flushed yet, there was no value, but # later, the object has been expired and detached, and *now* # they're trying to evaluate it # # * the object had a value, but it was changed to a new value, and # then expired # # * the object had a value, but it was changed to a new value, and # then expired, then the object was detached # # * the object has a user-set value, but it's None and we don't do # the comparison correctly for that so warn # prop = mapper.get_property_by_column(column) # by invoking this method, InstanceState will track the last known # value for this key each time the attribute is to be expired. # this feature was added explicitly for use in this method. state._track_last_known_value(prop.key) def _go(): last_known = to_return = state._last_known_values[prop.key] existing_is_available = last_known is not attributes.NO_VALUE # we support that the value may have changed. so here we # try to get the most recent value including re-fetching. # only if we can't get a value now due to detachment do we return # the last known value current_value = mapper._get_state_attr_by_column( state, dict_, column, passive=attributes.PASSIVE_OFF if state.persistent else attributes.PASSIVE_NO_FETCH ^ attributes.INIT_OK, ) if current_value is attributes.NEVER_SET: if not existing_is_available: raise sa_exc.InvalidRequestError( "Can't resolve value for column %s on object " "%s; no value has been set for this column" % (column, state_str(state)) ) elif current_value is attributes.PASSIVE_NO_RESULT: if not existing_is_available: raise sa_exc.InvalidRequestError( "Can't resolve value for column %s on object " "%s; the object is detached and the value was " "expired" % (column, state_str(state)) ) else: to_return = current_value if to_return is None: util.warn( "Got None for value of column %s; this is unsupported " "for a relationship comparison and will not " "currently produce an IS comparison " "(but may in a future release)" % column ) return to_return return _go def _lazy_none_clause(self, reverse_direction=False, adapt_source=None): if not reverse_direction: criterion, bind_to_col = ( self._lazy_strategy._lazywhere, self._lazy_strategy._bind_to_col, ) else: criterion, bind_to_col = ( self._lazy_strategy._rev_lazywhere, self._lazy_strategy._rev_bind_to_col, ) criterion = adapt_criterion_to_null(criterion, bind_to_col) if adapt_source: criterion = adapt_source(criterion) return criterion def __str__(self): return str(self.parent.class_.__name__) + "." + self.key def merge( self, session, source_state, source_dict, dest_state, dest_dict, load, _recursive, _resolve_conflict_map, ): if load: for r in self._reverse_property: if (source_state, r) in _recursive: return if "merge" not in self._cascade: return if self.key not in source_dict: return if self.uselist: impl = source_state.get_impl(self.key) instances_iterable = impl.get_collection(source_state, source_dict) # if this is a CollectionAttributeImpl, then empty should # be False, otherwise "self.key in source_dict" should not be # True assert not instances_iterable.empty if impl.collection else True if load: # for a full merge, pre-load the destination collection, # so that individual _merge of each item pulls from identity # map for those already present. # also assumes CollectionAttributeImpl behavior of loading # "old" list in any case dest_state.get_impl(self.key).get( dest_state, dest_dict, passive=PASSIVE_MERGE ) dest_list = [] for current in instances_iterable: current_state = attributes.instance_state(current) current_dict = attributes.instance_dict(current) _recursive[(current_state, self)] = True obj = session._merge( current_state, current_dict, load=load, _recursive=_recursive, _resolve_conflict_map=_resolve_conflict_map, ) if obj is not None: dest_list.append(obj) if not load: coll = attributes.init_state_collection( dest_state, dest_dict, self.key ) for c in dest_list: coll.append_without_event(c) else: dest_state.get_impl(self.key).set( dest_state, dest_dict, dest_list, _adapt=False, passive=PASSIVE_MERGE, ) else: current = source_dict[self.key] if current is not None: current_state = attributes.instance_state(current) current_dict = attributes.instance_dict(current) _recursive[(current_state, self)] = True obj = session._merge( current_state, current_dict, load=load, _recursive=_recursive, _resolve_conflict_map=_resolve_conflict_map, ) else: obj = None if not load: dest_dict[self.key] = obj else: dest_state.get_impl(self.key).set( dest_state, dest_dict, obj, None ) def _value_as_iterable( self, state, dict_, key, passive=attributes.PASSIVE_OFF ): """Return a list of tuples (state, obj) for the given key. returns an empty list if the value is None/empty/PASSIVE_NO_RESULT """ impl = state.manager[key].impl x = impl.get(state, dict_, passive=passive) if x is attributes.PASSIVE_NO_RESULT or x is None: return [] elif hasattr(impl, "get_collection"): return [ (attributes.instance_state(o), o) for o in impl.get_collection(state, dict_, x, passive=passive) ] else: return [(attributes.instance_state(x), x)] def cascade_iterator( self, type_, state, dict_, visited_states, halt_on=None ): # assert type_ in self._cascade # only actively lazy load on the 'delete' cascade if type_ != "delete" or self.passive_deletes: passive = attributes.PASSIVE_NO_INITIALIZE else: passive = attributes.PASSIVE_OFF if type_ == "save-update": tuples = state.manager[self.key].impl.get_all_pending(state, dict_) else: tuples = self._value_as_iterable( state, dict_, self.key, passive=passive ) skip_pending = ( type_ == "refresh-expire" and "delete-orphan" not in self._cascade ) for instance_state, c in tuples: if instance_state in visited_states: continue if c is None: # would like to emit a warning here, but # would not be consistent with collection.append(None) # current behavior of silently skipping. # see [ticket:2229] continue instance_dict = attributes.instance_dict(c) if halt_on and halt_on(instance_state): continue if skip_pending and not instance_state.key: continue instance_mapper = instance_state.manager.mapper if not instance_mapper.isa(self.mapper.class_manager.mapper): raise AssertionError( "Attribute '%s' on class '%s' " "doesn't handle objects " "of type '%s'" % (self.key, self.parent.class_, c.__class__) ) visited_states.add(instance_state) yield c, instance_mapper, instance_state, instance_dict @property def _effective_sync_backref(self): if self.viewonly: return False else: return self.sync_backref is not False @staticmethod def _check_sync_backref(rel_a, rel_b): if rel_a.viewonly and rel_b.sync_backref: raise sa_exc.InvalidRequestError( "Relationship %s cannot specify sync_backref=True since %s " "includes viewonly=True." % (rel_b, rel_a) ) if ( rel_a.viewonly and not rel_b.viewonly and rel_b.sync_backref is not False ): rel_b.sync_backref = False def _add_reverse_property(self, key): other = self.mapper.get_property(key, _configure_mappers=False) if not isinstance(other, RelationshipProperty): raise sa_exc.InvalidRequestError( "back_populates on relationship '%s' refers to attribute '%s' " "that is not a relationship. The back_populates parameter " "should refer to the name of a relationship on the target " "class." % (self, other) ) # viewonly and sync_backref cases # 1. self.viewonly==True and other.sync_backref==True -> error # 2. self.viewonly==True and other.viewonly==False and # other.sync_backref==None -> warn sync_backref=False, set to False self._check_sync_backref(self, other) # 3. other.viewonly==True and self.sync_backref==True -> error # 4. other.viewonly==True and self.viewonly==False and # self.sync_backref==None -> warn sync_backref=False, set to False self._check_sync_backref(other, self) self._reverse_property.add(other) other._reverse_property.add(self) if not other.mapper.common_parent(self.parent): raise sa_exc.ArgumentError( "reverse_property %r on " "relationship %s references relationship %s, which " "does not reference mapper %s" % (key, self, other, self.parent) ) if ( self.direction in (ONETOMANY, MANYTOONE) and self.direction == other.direction ): raise sa_exc.ArgumentError( "%s and back-reference %s are " "both of the same direction %r. Did you mean to " "set remote_side on the many-to-one side ?" % (other, self, self.direction) ) @util.memoized_property @util.preload_module("sqlalchemy.orm.mapper") def entity(self): """Return the target mapped entity, which is an inspect() of the class or aliased class that is referred towards. """ mapperlib = util.preloaded.orm_mapper if isinstance(self.argument, util.string_types): argument = self._clsregistry_resolve_name(self.argument)() elif callable(self.argument) and not isinstance( self.argument, (type, mapperlib.Mapper) ): argument = self.argument() else: argument = self.argument if isinstance(argument, type): return mapperlib.class_mapper(argument, configure=False) try: entity = inspect(argument) except sa_exc.NoInspectionAvailable: pass else: if hasattr(entity, "mapper"): return entity raise sa_exc.ArgumentError( "relationship '%s' expects " "a class or a mapper argument (received: %s)" % (self.key, type(argument)) ) @util.memoized_property def mapper(self): """Return the targeted :class:`_orm.Mapper` for this :class:`.RelationshipProperty`. This is a lazy-initializing static attribute. """ return self.entity.mapper def do_init(self): self._check_conflicts() self._process_dependent_arguments() self._setup_registry_dependencies() self._setup_join_conditions() self._check_cascade_settings(self._cascade) self._post_init() self._generate_backref() self._join_condition._warn_for_conflicting_sync_targets() super(RelationshipProperty, self).do_init() self._lazy_strategy = self._get_strategy((("lazy", "select"),)) def _setup_registry_dependencies(self): self.parent.mapper.registry._set_depends_on( self.entity.mapper.registry ) def _process_dependent_arguments(self): """Convert incoming configuration arguments to their proper form. Callables are resolved, ORM annotations removed. """ # accept callables for other attributes which may require # deferred initialization. This technique is used # by declarative "string configs" and some recipes. for attr in ( "order_by", "primaryjoin", "secondaryjoin", "secondary", "_user_defined_foreign_keys", "remote_side", ): attr_value = getattr(self, attr) if isinstance(attr_value, util.string_types): setattr( self, attr, self._clsregistry_resolve_arg( attr_value, favor_tables=attr == "secondary" )(), ) elif callable(attr_value) and not _is_mapped_class(attr_value): setattr(self, attr, attr_value()) # remove "annotations" which are present if mapped class # descriptors are used to create the join expression. for attr in "primaryjoin", "secondaryjoin": val = getattr(self, attr) if val is not None: setattr( self, attr, _orm_deannotate( coercions.expect( roles.ColumnArgumentRole, val, argname=attr ) ), ) if self.secondary is not None and _is_mapped_class(self.secondary): raise sa_exc.ArgumentError( "secondary argument %s passed to to relationship() %s must " "be a Table object or other FROM clause; can't send a mapped " "class directly as rows in 'secondary' are persisted " "independently of a class that is mapped " "to that same table." % (self.secondary, self) ) # ensure expressions in self.order_by, foreign_keys, # remote_side are all columns, not strings. if self.order_by is not False and self.order_by is not None: self.order_by = tuple( coercions.expect( roles.ColumnArgumentRole, x, argname="order_by" ) for x in util.to_list(self.order_by) ) self._user_defined_foreign_keys = util.column_set( coercions.expect( roles.ColumnArgumentRole, x, argname="foreign_keys" ) for x in util.to_column_set(self._user_defined_foreign_keys) ) self.remote_side = util.column_set( coercions.expect( roles.ColumnArgumentRole, x, argname="remote_side" ) for x in util.to_column_set(self.remote_side) ) self.target = self.entity.persist_selectable def _setup_join_conditions(self): self._join_condition = jc = JoinCondition( parent_persist_selectable=self.parent.persist_selectable, child_persist_selectable=self.entity.persist_selectable, parent_local_selectable=self.parent.local_table, child_local_selectable=self.entity.local_table, primaryjoin=self.primaryjoin, secondary=self.secondary, secondaryjoin=self.secondaryjoin, parent_equivalents=self.parent._equivalent_columns, child_equivalents=self.mapper._equivalent_columns, consider_as_foreign_keys=self._user_defined_foreign_keys, local_remote_pairs=self.local_remote_pairs, remote_side=self.remote_side, self_referential=self._is_self_referential, prop=self, support_sync=not self.viewonly, can_be_synced_fn=self._columns_are_mapped, ) self.primaryjoin = jc.primaryjoin self.secondaryjoin = jc.secondaryjoin self.direction = jc.direction self.local_remote_pairs = jc.local_remote_pairs self.remote_side = jc.remote_columns self.local_columns = jc.local_columns self.synchronize_pairs = jc.synchronize_pairs self._calculated_foreign_keys = jc.foreign_key_columns self.secondary_synchronize_pairs = jc.secondary_synchronize_pairs @property def _clsregistry_resolve_arg(self): return self._clsregistry_resolvers[1] @property def _clsregistry_resolve_name(self): return self._clsregistry_resolvers[0] @util.memoized_property @util.preload_module("sqlalchemy.orm.clsregistry") def _clsregistry_resolvers(self): _resolver = util.preloaded.orm_clsregistry._resolver return _resolver(self.parent.class_, self) @util.preload_module("sqlalchemy.orm.mapper") def _check_conflicts(self): """Test that this relationship is legal, warn about inheritance conflicts.""" mapperlib = util.preloaded.orm_mapper if self.parent.non_primary and not mapperlib.class_mapper( self.parent.class_, configure=False ).has_property(self.key): raise sa_exc.ArgumentError( "Attempting to assign a new " "relationship '%s' to a non-primary mapper on " "class '%s'. New relationships can only be added " "to the primary mapper, i.e. the very first mapper " "created for class '%s' " % ( self.key, self.parent.class_.__name__, self.parent.class_.__name__, ) ) @property def cascade(self): """Return the current cascade setting for this :class:`.RelationshipProperty`. """ return self._cascade @cascade.setter def cascade(self, cascade): self._set_cascade(cascade) def _set_cascade(self, cascade): cascade = CascadeOptions(cascade) if self.viewonly: non_viewonly = set(cascade).difference( CascadeOptions._viewonly_cascades ) if non_viewonly: raise sa_exc.ArgumentError( 'Cascade settings "%s" apply to persistence operations ' "and should not be combined with a viewonly=True " "relationship." % (", ".join(sorted(non_viewonly))) ) if "mapper" in self.__dict__: self._check_cascade_settings(cascade) self._cascade = cascade if self._dependency_processor: self._dependency_processor.cascade = cascade def _check_cascade_settings(self, cascade): if ( cascade.delete_orphan and not self.single_parent and (self.direction is MANYTOMANY or self.direction is MANYTOONE) ): raise sa_exc.ArgumentError( "For %(direction)s relationship %(rel)s, delete-orphan " "cascade is normally " 'configured only on the "one" side of a one-to-many ' "relationship, " 'and not on the "many" side of a many-to-one or many-to-many ' "relationship. " "To force this relationship to allow a particular " '"%(relatedcls)s" object to be referred towards by only ' 'a single "%(clsname)s" object at a time via the ' "%(rel)s relationship, which " "would allow " "delete-orphan cascade to take place in this direction, set " "the single_parent=True flag." % { "rel": self, "direction": "many-to-one" if self.direction is MANYTOONE else "many-to-many", "clsname": self.parent.class_.__name__, "relatedcls": self.mapper.class_.__name__, }, code="bbf0", ) if self.passive_deletes == "all" and ( "delete" in cascade or "delete-orphan" in cascade ): raise sa_exc.ArgumentError( "On %s, can't set passive_deletes='all' in conjunction " "with 'delete' or 'delete-orphan' cascade" % self ) if cascade.delete_orphan: self.mapper.primary_mapper()._delete_orphans.append( (self.key, self.parent.class_) ) def _persists_for(self, mapper): """Return True if this property will persist values on behalf of the given mapper. """ return ( self.key in mapper.relationships and mapper.relationships[self.key] is self ) def _columns_are_mapped(self, *cols): """Return True if all columns in the given collection are mapped by the tables referenced by this :class:`.Relationship`. """ for c in cols: if ( self.secondary is not None and self.secondary.c.contains_column(c) ): continue if not self.parent.persist_selectable.c.contains_column( c ) and not self.target.c.contains_column(c): return False return True def _generate_backref(self): """Interpret the 'backref' instruction to create a :func:`_orm.relationship` complementary to this one.""" if self.parent.non_primary: return if self.backref is not None and not self.back_populates: if isinstance(self.backref, util.string_types): backref_key, kwargs = self.backref, {} else: backref_key, kwargs = self.backref mapper = self.mapper.primary_mapper() if not mapper.concrete: check = set(mapper.iterate_to_root()).union( mapper.self_and_descendants ) for m in check: if m.has_property(backref_key) and not m.concrete: raise sa_exc.ArgumentError( "Error creating backref " "'%s' on relationship '%s': property of that " "name exists on mapper '%s'" % (backref_key, self, m) ) # determine primaryjoin/secondaryjoin for the # backref. Use the one we had, so that # a custom join doesn't have to be specified in # both directions. if self.secondary is not None: # for many to many, just switch primaryjoin/ # secondaryjoin. use the annotated # pj/sj on the _join_condition. pj = kwargs.pop( "primaryjoin", self._join_condition.secondaryjoin_minus_local, ) sj = kwargs.pop( "secondaryjoin", self._join_condition.primaryjoin_minus_local, ) else: pj = kwargs.pop( "primaryjoin", self._join_condition.primaryjoin_reverse_remote, ) sj = kwargs.pop("secondaryjoin", None) if sj: raise sa_exc.InvalidRequestError( "Can't assign 'secondaryjoin' on a backref " "against a non-secondary relationship." ) foreign_keys = kwargs.pop( "foreign_keys", self._user_defined_foreign_keys ) parent = self.parent.primary_mapper() kwargs.setdefault("viewonly", self.viewonly) kwargs.setdefault("post_update", self.post_update) kwargs.setdefault("passive_updates", self.passive_updates) kwargs.setdefault("sync_backref", self.sync_backref) self.back_populates = backref_key relationship = RelationshipProperty( parent, self.secondary, pj, sj, foreign_keys=foreign_keys, back_populates=self.key, **kwargs ) mapper._configure_property(backref_key, relationship) if self.back_populates: self._add_reverse_property(self.back_populates) @util.preload_module("sqlalchemy.orm.dependency") def _post_init(self): dependency = util.preloaded.orm_dependency if self.uselist is None: self.uselist = self.direction is not MANYTOONE if not self.viewonly: self._dependency_processor = ( dependency.DependencyProcessor.from_relationship )(self) @util.memoized_property def _use_get(self): """memoize the 'use_get' attribute of this RelationshipLoader's lazyloader.""" strategy = self._lazy_strategy return strategy.use_get @util.memoized_property def _is_self_referential(self): return self.mapper.common_parent(self.parent) def _create_joins( self, source_polymorphic=False, source_selectable=None, dest_selectable=None, of_type_entity=None, alias_secondary=False, extra_criteria=(), ): aliased = False if alias_secondary and self.secondary is not None: aliased = True if source_selectable is None: if source_polymorphic and self.parent.with_polymorphic: source_selectable = self.parent._with_polymorphic_selectable if of_type_entity: dest_mapper = of_type_entity.mapper if dest_selectable is None: dest_selectable = of_type_entity.selectable aliased = True else: dest_mapper = self.mapper if dest_selectable is None: dest_selectable = self.entity.selectable if self.mapper.with_polymorphic: aliased = True if self._is_self_referential and source_selectable is None: dest_selectable = dest_selectable._anonymous_fromclause() aliased = True elif ( dest_selectable is not self.mapper._with_polymorphic_selectable or self.mapper.with_polymorphic ): aliased = True single_crit = dest_mapper._single_table_criterion aliased = aliased or ( source_selectable is not None and ( source_selectable is not self.parent._with_polymorphic_selectable or source_selectable._is_subquery ) ) ( primaryjoin, secondaryjoin, secondary, target_adapter, dest_selectable, ) = self._join_condition.join_targets( source_selectable, dest_selectable, aliased, single_crit, extra_criteria, ) if source_selectable is None: source_selectable = self.parent.local_table if dest_selectable is None: dest_selectable = self.entity.local_table return ( primaryjoin, secondaryjoin, source_selectable, dest_selectable, secondary, target_adapter, ) def _annotate_columns(element, annotations): def clone(elem): if isinstance(elem, expression.ColumnClause): elem = elem._annotate(annotations.copy()) elem._copy_internals(clone=clone) return elem if element is not None: element = clone(element) clone = None # remove gc cycles return element class JoinCondition(object): def __init__( self, parent_persist_selectable, child_persist_selectable, parent_local_selectable, child_local_selectable, primaryjoin=None, secondary=None, secondaryjoin=None, parent_equivalents=None, child_equivalents=None, consider_as_foreign_keys=None, local_remote_pairs=None, remote_side=None, self_referential=False, prop=None, support_sync=True, can_be_synced_fn=lambda *c: True, ): self.parent_persist_selectable = parent_persist_selectable self.parent_local_selectable = parent_local_selectable self.child_persist_selectable = child_persist_selectable self.child_local_selectable = child_local_selectable self.parent_equivalents = parent_equivalents self.child_equivalents = child_equivalents self.primaryjoin = primaryjoin self.secondaryjoin = secondaryjoin self.secondary = secondary self.consider_as_foreign_keys = consider_as_foreign_keys self._local_remote_pairs = local_remote_pairs self._remote_side = remote_side self.prop = prop self.self_referential = self_referential self.support_sync = support_sync self.can_be_synced_fn = can_be_synced_fn self._determine_joins() self._sanitize_joins() self._annotate_fks() self._annotate_remote() self._annotate_local() self._annotate_parentmapper() self._setup_pairs() self._check_foreign_cols(self.primaryjoin, True) if self.secondaryjoin is not None: self._check_foreign_cols(self.secondaryjoin, False) self._determine_direction() self._check_remote_side() self._log_joins() def _log_joins(self): if self.prop is None: return log = self.prop.logger log.info("%s setup primary join %s", self.prop, self.primaryjoin) log.info("%s setup secondary join %s", self.prop, self.secondaryjoin) log.info( "%s synchronize pairs [%s]", self.prop, ",".join( "(%s => %s)" % (l, r) for (l, r) in self.synchronize_pairs ), ) log.info( "%s secondary synchronize pairs [%s]", self.prop, ",".join( "(%s => %s)" % (l, r) for (l, r) in self.secondary_synchronize_pairs or [] ), ) log.info( "%s local/remote pairs [%s]", self.prop, ",".join( "(%s / %s)" % (l, r) for (l, r) in self.local_remote_pairs ), ) log.info( "%s remote columns [%s]", self.prop, ",".join("%s" % col for col in self.remote_columns), ) log.info( "%s local columns [%s]", self.prop, ",".join("%s" % col for col in self.local_columns), ) log.info("%s relationship direction %s", self.prop, self.direction) def _sanitize_joins(self): """remove the parententity annotation from our join conditions which can leak in here based on some declarative patterns and maybe others. We'd want to remove "parentmapper" also, but apparently there's an exotic use case in _join_fixture_inh_selfref_w_entity that relies upon it being present, see :ticket:`3364`. """ self.primaryjoin = _deep_deannotate( self.primaryjoin, values=("parententity", "proxy_key") ) if self.secondaryjoin is not None: self.secondaryjoin = _deep_deannotate( self.secondaryjoin, values=("parententity", "proxy_key") ) def _determine_joins(self): """Determine the 'primaryjoin' and 'secondaryjoin' attributes, if not passed to the constructor already. This is based on analysis of the foreign key relationships between the parent and target mapped selectables. """ if self.secondaryjoin is not None and self.secondary is None: raise sa_exc.ArgumentError( "Property %s specified with secondary " "join condition but " "no secondary argument" % self.prop ) # find a join between the given mapper's mapped table and # the given table. will try the mapper's local table first # for more specificity, then if not found will try the more # general mapped table, which in the case of inheritance is # a join. try: consider_as_foreign_keys = self.consider_as_foreign_keys or None if self.secondary is not None: if self.secondaryjoin is None: self.secondaryjoin = join_condition( self.child_persist_selectable, self.secondary, a_subset=self.child_local_selectable, consider_as_foreign_keys=consider_as_foreign_keys, ) if self.primaryjoin is None: self.primaryjoin = join_condition( self.parent_persist_selectable, self.secondary, a_subset=self.parent_local_selectable, consider_as_foreign_keys=consider_as_foreign_keys, ) else: if self.primaryjoin is None: self.primaryjoin = join_condition( self.parent_persist_selectable, self.child_persist_selectable, a_subset=self.parent_local_selectable, consider_as_foreign_keys=consider_as_foreign_keys, ) except sa_exc.NoForeignKeysError as nfe: if self.secondary is not None: util.raise_( sa_exc.NoForeignKeysError( "Could not determine join " "condition between parent/child tables on " "relationship %s - there are no foreign keys " "linking these tables via secondary table '%s'. " "Ensure that referencing columns are associated " "with a ForeignKey or ForeignKeyConstraint, or " "specify 'primaryjoin' and 'secondaryjoin' " "expressions." % (self.prop, self.secondary) ), from_=nfe, ) else: util.raise_( sa_exc.NoForeignKeysError( "Could not determine join " "condition between parent/child tables on " "relationship %s - there are no foreign keys " "linking these tables. " "Ensure that referencing columns are associated " "with a ForeignKey or ForeignKeyConstraint, or " "specify a 'primaryjoin' expression." % self.prop ), from_=nfe, ) except sa_exc.AmbiguousForeignKeysError as afe: if self.secondary is not None: util.raise_( sa_exc.AmbiguousForeignKeysError( "Could not determine join " "condition between parent/child tables on " "relationship %s - there are multiple foreign key " "paths linking the tables via secondary table '%s'. " "Specify the 'foreign_keys' " "argument, providing a list of those columns which " "should be counted as containing a foreign key " "reference from the secondary table to each of the " "parent and child tables." % (self.prop, self.secondary) ), from_=afe, ) else: util.raise_( sa_exc.AmbiguousForeignKeysError( "Could not determine join " "condition between parent/child tables on " "relationship %s - there are multiple foreign key " "paths linking the tables. Specify the " "'foreign_keys' argument, providing a list of those " "columns which should be counted as containing a " "foreign key reference to the parent table." % self.prop ), from_=afe, ) @property def primaryjoin_minus_local(self): return _deep_deannotate(self.primaryjoin, values=("local", "remote")) @property def secondaryjoin_minus_local(self): return _deep_deannotate(self.secondaryjoin, values=("local", "remote")) @util.memoized_property def primaryjoin_reverse_remote(self): """Return the primaryjoin condition suitable for the "reverse" direction. If the primaryjoin was delivered here with pre-existing "remote" annotations, the local/remote annotations are reversed. Otherwise, the local/remote annotations are removed. """ if self._has_remote_annotations: def replace(element): if "remote" in element._annotations: v = dict(element._annotations) del v["remote"] v["local"] = True return element._with_annotations(v) elif "local" in element._annotations: v = dict(element._annotations) del v["local"] v["remote"] = True return element._with_annotations(v) return visitors.replacement_traverse(self.primaryjoin, {}, replace) else: if self._has_foreign_annotations: # TODO: coverage return _deep_deannotate( self.primaryjoin, values=("local", "remote") ) else: return _deep_deannotate(self.primaryjoin) def _has_annotation(self, clause, annotation): for col in visitors.iterate(clause, {}): if annotation in col._annotations: return True else: return False @util.memoized_property def _has_foreign_annotations(self): return self._has_annotation(self.primaryjoin, "foreign") @util.memoized_property def _has_remote_annotations(self): return self._has_annotation(self.primaryjoin, "remote") def _annotate_fks(self): """Annotate the primaryjoin and secondaryjoin structures with 'foreign' annotations marking columns considered as foreign. """ if self._has_foreign_annotations: return if self.consider_as_foreign_keys: self._annotate_from_fk_list() else: self._annotate_present_fks() def _annotate_from_fk_list(self): def check_fk(col): if col in self.consider_as_foreign_keys: return col._annotate({"foreign": True}) self.primaryjoin = visitors.replacement_traverse( self.primaryjoin, {}, check_fk ) if self.secondaryjoin is not None: self.secondaryjoin = visitors.replacement_traverse( self.secondaryjoin, {}, check_fk ) def _annotate_present_fks(self): if self.secondary is not None: secondarycols = util.column_set(self.secondary.c) else: secondarycols = set() def is_foreign(a, b): if isinstance(a, schema.Column) and isinstance(b, schema.Column): if a.references(b): return a elif b.references(a): return b if secondarycols: if a in secondarycols and b not in secondarycols: return a elif b in secondarycols and a not in secondarycols: return b def visit_binary(binary): if not isinstance( binary.left, sql.ColumnElement ) or not isinstance(binary.right, sql.ColumnElement): return if ( "foreign" not in binary.left._annotations and "foreign" not in binary.right._annotations ): col = is_foreign(binary.left, binary.right) if col is not None: if col.compare(binary.left): binary.left = binary.left._annotate({"foreign": True}) elif col.compare(binary.right): binary.right = binary.right._annotate( {"foreign": True} ) self.primaryjoin = visitors.cloned_traverse( self.primaryjoin, {}, {"binary": visit_binary} ) if self.secondaryjoin is not None: self.secondaryjoin = visitors.cloned_traverse( self.secondaryjoin, {}, {"binary": visit_binary} ) def _refers_to_parent_table(self): """Return True if the join condition contains column comparisons where both columns are in both tables. """ pt = self.parent_persist_selectable mt = self.child_persist_selectable result = [False] def visit_binary(binary): c, f = binary.left, binary.right if ( isinstance(c, expression.ColumnClause) and isinstance(f, expression.ColumnClause) and pt.is_derived_from(c.table) and pt.is_derived_from(f.table) and mt.is_derived_from(c.table) and mt.is_derived_from(f.table) ): result[0] = True visitors.traverse(self.primaryjoin, {}, {"binary": visit_binary}) return result[0] def _tables_overlap(self): """Return True if parent/child tables have some overlap.""" return selectables_overlap( self.parent_persist_selectable, self.child_persist_selectable ) def _annotate_remote(self): """Annotate the primaryjoin and secondaryjoin structures with 'remote' annotations marking columns considered as part of the 'remote' side. """ if self._has_remote_annotations: return if self.secondary is not None: self._annotate_remote_secondary() elif self._local_remote_pairs or self._remote_side: self._annotate_remote_from_args() elif self._refers_to_parent_table(): self._annotate_selfref( lambda col: "foreign" in col._annotations, False ) elif self._tables_overlap(): self._annotate_remote_with_overlap() else: self._annotate_remote_distinct_selectables() def _annotate_remote_secondary(self): """annotate 'remote' in primaryjoin, secondaryjoin when 'secondary' is present. """ def repl(element): if self.secondary.c.contains_column(element): return element._annotate({"remote": True}) self.primaryjoin = visitors.replacement_traverse( self.primaryjoin, {}, repl ) self.secondaryjoin = visitors.replacement_traverse( self.secondaryjoin, {}, repl ) def _annotate_selfref(self, fn, remote_side_given): """annotate 'remote' in primaryjoin, secondaryjoin when the relationship is detected as self-referential. """ def visit_binary(binary): equated = binary.left.compare(binary.right) if isinstance(binary.left, expression.ColumnClause) and isinstance( binary.right, expression.ColumnClause ): # assume one to many - FKs are "remote" if fn(binary.left): binary.left = binary.left._annotate({"remote": True}) if fn(binary.right) and not equated: binary.right = binary.right._annotate({"remote": True}) elif not remote_side_given: self._warn_non_column_elements() self.primaryjoin = visitors.cloned_traverse( self.primaryjoin, {}, {"binary": visit_binary} ) def _annotate_remote_from_args(self): """annotate 'remote' in primaryjoin, secondaryjoin when the 'remote_side' or '_local_remote_pairs' arguments are used. """ if self._local_remote_pairs: if self._remote_side: raise sa_exc.ArgumentError( "remote_side argument is redundant " "against more detailed _local_remote_side " "argument." ) remote_side = [r for (l, r) in self._local_remote_pairs] else: remote_side = self._remote_side if self._refers_to_parent_table(): self._annotate_selfref(lambda col: col in remote_side, True) else: def repl(element): # use set() to avoid generating ``__eq__()`` expressions # against each element if element in set(remote_side): return element._annotate({"remote": True}) self.primaryjoin = visitors.replacement_traverse( self.primaryjoin, {}, repl ) def _annotate_remote_with_overlap(self): """annotate 'remote' in primaryjoin, secondaryjoin when the parent/child tables have some set of tables in common, though is not a fully self-referential relationship. """ def visit_binary(binary): binary.left, binary.right = proc_left_right( binary.left, binary.right ) binary.right, binary.left = proc_left_right( binary.right, binary.left ) check_entities = ( self.prop is not None and self.prop.mapper is not self.prop.parent ) def proc_left_right(left, right): if isinstance(left, expression.ColumnClause) and isinstance( right, expression.ColumnClause ): if self.child_persist_selectable.c.contains_column( right ) and self.parent_persist_selectable.c.contains_column(left): right = right._annotate({"remote": True}) elif ( check_entities and right._annotations.get("parentmapper") is self.prop.mapper ): right = right._annotate({"remote": True}) elif ( check_entities and left._annotations.get("parentmapper") is self.prop.mapper ): left = left._annotate({"remote": True}) else: self._warn_non_column_elements() return left, right self.primaryjoin = visitors.cloned_traverse( self.primaryjoin, {}, {"binary": visit_binary} ) def _annotate_remote_distinct_selectables(self): """annotate 'remote' in primaryjoin, secondaryjoin when the parent/child tables are entirely separate. """ def repl(element): if self.child_persist_selectable.c.contains_column(element) and ( not self.parent_local_selectable.c.contains_column(element) or self.child_local_selectable.c.contains_column(element) ): return element._annotate({"remote": True}) self.primaryjoin = visitors.replacement_traverse( self.primaryjoin, {}, repl ) def _warn_non_column_elements(self): util.warn( "Non-simple column elements in primary " "join condition for property %s - consider using " "remote() annotations to mark the remote side." % self.prop ) def _annotate_local(self): """Annotate the primaryjoin and secondaryjoin structures with 'local' annotations. This annotates all column elements found simultaneously in the parent table and the join condition that don't have a 'remote' annotation set up from _annotate_remote() or user-defined. """ if self._has_annotation(self.primaryjoin, "local"): return if self._local_remote_pairs: local_side = util.column_set( [l for (l, r) in self._local_remote_pairs] ) else: local_side = util.column_set(self.parent_persist_selectable.c) def locals_(elem): if "remote" not in elem._annotations and elem in local_side: return elem._annotate({"local": True}) self.primaryjoin = visitors.replacement_traverse( self.primaryjoin, {}, locals_ ) def _annotate_parentmapper(self): if self.prop is None: return def parentmappers_(elem): if "remote" in elem._annotations: return elem._annotate({"parentmapper": self.prop.mapper}) elif "local" in elem._annotations: return elem._annotate({"parentmapper": self.prop.parent}) self.primaryjoin = visitors.replacement_traverse( self.primaryjoin, {}, parentmappers_ ) def _check_remote_side(self): if not self.local_remote_pairs: raise sa_exc.ArgumentError( "Relationship %s could " "not determine any unambiguous local/remote column " "pairs based on join condition and remote_side " "arguments. " "Consider using the remote() annotation to " "accurately mark those elements of the join " "condition that are on the remote side of " "the relationship." % (self.prop,) ) else: not_target = util.column_set( self.parent_persist_selectable.c ).difference(self.child_persist_selectable.c) for _, rmt in self.local_remote_pairs: if rmt in not_target: util.warn( "Expression %s is marked as 'remote', but these " "column(s) are local to the local side. The " "remote() annotation is needed only for a " "self-referential relationship where both sides " "of the relationship refer to the same tables." % (rmt,) ) def _check_foreign_cols(self, join_condition, primary): """Check the foreign key columns collected and emit error messages.""" can_sync = False foreign_cols = self._gather_columns_with_annotation( join_condition, "foreign" ) has_foreign = bool(foreign_cols) if primary: can_sync = bool(self.synchronize_pairs) else: can_sync = bool(self.secondary_synchronize_pairs) if ( self.support_sync and can_sync or (not self.support_sync and has_foreign) ): return # from here below is just determining the best error message # to report. Check for a join condition using any operator # (not just ==), perhaps they need to turn on "viewonly=True". if self.support_sync and has_foreign and not can_sync: err = ( "Could not locate any simple equality expressions " "involving locally mapped foreign key columns for " "%s join condition " "'%s' on relationship %s." % ( primary and "primary" or "secondary", join_condition, self.prop, ) ) err += ( " Ensure that referencing columns are associated " "with a ForeignKey or ForeignKeyConstraint, or are " "annotated in the join condition with the foreign() " "annotation. To allow comparison operators other than " "'==', the relationship can be marked as viewonly=True." ) raise sa_exc.ArgumentError(err) else: err = ( "Could not locate any relevant foreign key columns " "for %s join condition '%s' on relationship %s." % ( primary and "primary" or "secondary", join_condition, self.prop, ) ) err += ( " Ensure that referencing columns are associated " "with a ForeignKey or ForeignKeyConstraint, or are " "annotated in the join condition with the foreign() " "annotation." ) raise sa_exc.ArgumentError(err) def _determine_direction(self): """Determine if this relationship is one to many, many to one, many to many. """ if self.secondaryjoin is not None: self.direction = MANYTOMANY else: parentcols = util.column_set(self.parent_persist_selectable.c) targetcols = util.column_set(self.child_persist_selectable.c) # fk collection which suggests ONETOMANY. onetomany_fk = targetcols.intersection(self.foreign_key_columns) # fk collection which suggests MANYTOONE. manytoone_fk = parentcols.intersection(self.foreign_key_columns) if onetomany_fk and manytoone_fk: # fks on both sides. test for overlap of local/remote # with foreign key. # we will gather columns directly from their annotations # without deannotating, so that we can distinguish on a column # that refers to itself. # 1. columns that are both remote and FK suggest # onetomany. onetomany_local = self._gather_columns_with_annotation( self.primaryjoin, "remote", "foreign" ) # 2. columns that are FK but are not remote (e.g. local) # suggest manytoone. manytoone_local = set( [ c for c in self._gather_columns_with_annotation( self.primaryjoin, "foreign" ) if "remote" not in c._annotations ] ) # 3. if both collections are present, remove columns that # refer to themselves. This is for the case of # and_(Me.id == Me.remote_id, Me.version == Me.version) if onetomany_local and manytoone_local: self_equated = self.remote_columns.intersection( self.local_columns ) onetomany_local = onetomany_local.difference(self_equated) manytoone_local = manytoone_local.difference(self_equated) # at this point, if only one or the other collection is # present, we know the direction, otherwise it's still # ambiguous. if onetomany_local and not manytoone_local: self.direction = ONETOMANY elif manytoone_local and not onetomany_local: self.direction = MANYTOONE else: raise sa_exc.ArgumentError( "Can't determine relationship" " direction for relationship '%s' - foreign " "key columns within the join condition are present " "in both the parent and the child's mapped tables. " "Ensure that only those columns referring " "to a parent column are marked as foreign, " "either via the foreign() annotation or " "via the foreign_keys argument." % self.prop ) elif onetomany_fk: self.direction = ONETOMANY elif manytoone_fk: self.direction = MANYTOONE else: raise sa_exc.ArgumentError( "Can't determine relationship " "direction for relationship '%s' - foreign " "key columns are present in neither the parent " "nor the child's mapped tables" % self.prop ) def _deannotate_pairs(self, collection): """provide deannotation for the various lists of pairs, so that using them in hashes doesn't incur high-overhead __eq__() comparisons against original columns mapped. """ return [(x._deannotate(), y._deannotate()) for x, y in collection] def _setup_pairs(self): sync_pairs = [] lrp = util.OrderedSet([]) secondary_sync_pairs = [] def go(joincond, collection): def visit_binary(binary, left, right): if ( "remote" in right._annotations and "remote" not in left._annotations and self.can_be_synced_fn(left) ): lrp.add((left, right)) elif ( "remote" in left._annotations and "remote" not in right._annotations and self.can_be_synced_fn(right) ): lrp.add((right, left)) if binary.operator is operators.eq and self.can_be_synced_fn( left, right ): if "foreign" in right._annotations: collection.append((left, right)) elif "foreign" in left._annotations: collection.append((right, left)) visit_binary_product(visit_binary, joincond) for joincond, collection in [ (self.primaryjoin, sync_pairs), (self.secondaryjoin, secondary_sync_pairs), ]: if joincond is None: continue go(joincond, collection) self.local_remote_pairs = self._deannotate_pairs(lrp) self.synchronize_pairs = self._deannotate_pairs(sync_pairs) self.secondary_synchronize_pairs = self._deannotate_pairs( secondary_sync_pairs ) _track_overlapping_sync_targets = weakref.WeakKeyDictionary() def _warn_for_conflicting_sync_targets(self): if not self.support_sync: return # we would like to detect if we are synchronizing any column # pairs in conflict with another relationship that wishes to sync # an entirely different column to the same target. This is a # very rare edge case so we will try to minimize the memory/overhead # impact of this check for from_, to_ in [ (from_, to_) for (from_, to_) in self.synchronize_pairs ] + [ (from_, to_) for (from_, to_) in self.secondary_synchronize_pairs ]: # save ourselves a ton of memory and overhead by only # considering columns that are subject to a overlapping # FK constraints at the core level. This condition can arise # if multiple relationships overlap foreign() directly, but # we're going to assume it's typically a ForeignKeyConstraint- # level configuration that benefits from this warning. if to_ not in self._track_overlapping_sync_targets: self._track_overlapping_sync_targets[ to_ ] = weakref.WeakKeyDictionary({self.prop: from_}) else: other_props = [] prop_to_from = self._track_overlapping_sync_targets[to_] for pr, fr_ in prop_to_from.items(): if ( not pr.mapper._dispose_called and pr not in self.prop._reverse_property and pr.key not in self.prop._overlaps and self.prop.key not in pr._overlaps # note: the "__*" symbol is used internally by # SQLAlchemy as a general means of suppressing the # overlaps warning for some extension cases, however # this is not currently # a publicly supported symbol and may change at # any time. and "__*" not in self.prop._overlaps and "__*" not in pr._overlaps and not self.prop.parent.is_sibling(pr.parent) and not self.prop.mapper.is_sibling(pr.mapper) and not self.prop.parent.is_sibling(pr.mapper) and not self.prop.mapper.is_sibling(pr.parent) and ( self.prop.key != pr.key or not self.prop.parent.common_parent(pr.parent) ) ): other_props.append((pr, fr_)) if other_props: util.warn( "relationship '%s' will copy column %s to column %s, " "which conflicts with relationship(s): %s. " "If this is not the intention, consider if these " "relationships should be linked with " "back_populates, or if viewonly=True should be " "applied to one or more if they are read-only. " "For the less common case that foreign key " "constraints are partially overlapping, the " "orm.foreign() " "annotation can be used to isolate the columns that " "should be written towards. To silence this " "warning, add the parameter 'overlaps=\"%s\"' to the " "'%s' relationship." % ( self.prop, from_, to_, ", ".join( sorted( "'%s' (copies %s to %s)" % (pr, fr_, to_) for (pr, fr_) in other_props ) ), ",".join(sorted(pr.key for pr, fr in other_props)), self.prop, ), code="qzyx", ) self._track_overlapping_sync_targets[to_][self.prop] = from_ @util.memoized_property def remote_columns(self): return self._gather_join_annotations("remote") @util.memoized_property def local_columns(self): return self._gather_join_annotations("local") @util.memoized_property def foreign_key_columns(self): return self._gather_join_annotations("foreign") def _gather_join_annotations(self, annotation): s = set( self._gather_columns_with_annotation(self.primaryjoin, annotation) ) if self.secondaryjoin is not None: s.update( self._gather_columns_with_annotation( self.secondaryjoin, annotation ) ) return {x._deannotate() for x in s} def _gather_columns_with_annotation(self, clause, *annotation): annotation = set(annotation) return set( [ col for col in visitors.iterate(clause, {}) if annotation.issubset(col._annotations) ] ) def join_targets( self, source_selectable, dest_selectable, aliased, single_crit=None, extra_criteria=(), ): """Given a source and destination selectable, create a join between them. This takes into account aliasing the join clause to reference the appropriate corresponding columns in the target objects, as well as the extra child criterion, equivalent column sets, etc. """ # place a barrier on the destination such that # replacement traversals won't ever dig into it. # its internal structure remains fixed # regardless of context. dest_selectable = _shallow_annotate( dest_selectable, {"no_replacement_traverse": True} ) primaryjoin, secondaryjoin, secondary = ( self.primaryjoin, self.secondaryjoin, self.secondary, ) # adjust the join condition for single table inheritance, # in the case that the join is to a subclass # this is analogous to the # "_adjust_for_single_table_inheritance()" method in Query. if single_crit is not None: if secondaryjoin is not None: secondaryjoin = secondaryjoin & single_crit else: primaryjoin = primaryjoin & single_crit if extra_criteria: if secondaryjoin is not None: secondaryjoin = secondaryjoin & sql.and_(*extra_criteria) else: primaryjoin = primaryjoin & sql.and_(*extra_criteria) if aliased: if secondary is not None: secondary = secondary._anonymous_fromclause(flat=True) primary_aliasizer = ClauseAdapter( secondary, exclude_fn=_ColInAnnotations("local") ) secondary_aliasizer = ClauseAdapter( dest_selectable, equivalents=self.child_equivalents ).chain(primary_aliasizer) if source_selectable is not None: primary_aliasizer = ClauseAdapter( secondary, exclude_fn=_ColInAnnotations("local") ).chain( ClauseAdapter( source_selectable, equivalents=self.parent_equivalents, ) ) secondaryjoin = secondary_aliasizer.traverse(secondaryjoin) else: primary_aliasizer = ClauseAdapter( dest_selectable, exclude_fn=_ColInAnnotations("local"), equivalents=self.child_equivalents, ) if source_selectable is not None: primary_aliasizer.chain( ClauseAdapter( source_selectable, exclude_fn=_ColInAnnotations("remote"), equivalents=self.parent_equivalents, ) ) secondary_aliasizer = None primaryjoin = primary_aliasizer.traverse(primaryjoin) target_adapter = secondary_aliasizer or primary_aliasizer target_adapter.exclude_fn = None else: target_adapter = None return ( primaryjoin, secondaryjoin, secondary, target_adapter, dest_selectable, ) def create_lazy_clause(self, reverse_direction=False): binds = util.column_dict() equated_columns = util.column_dict() has_secondary = self.secondaryjoin is not None if has_secondary: lookup = collections.defaultdict(list) for l, r in self.local_remote_pairs: lookup[l].append((l, r)) equated_columns[r] = l elif not reverse_direction: for l, r in self.local_remote_pairs: equated_columns[r] = l else: for l, r in self.local_remote_pairs: equated_columns[l] = r def col_to_bind(col): if ( (not reverse_direction and "local" in col._annotations) or reverse_direction and ( (has_secondary and col in lookup) or (not has_secondary and "remote" in col._annotations) ) ): if col not in binds: binds[col] = sql.bindparam( None, None, type_=col.type, unique=True ) return binds[col] return None lazywhere = self.primaryjoin if self.secondaryjoin is None or not reverse_direction: lazywhere = visitors.replacement_traverse( lazywhere, {}, col_to_bind ) if self.secondaryjoin is not None: secondaryjoin = self.secondaryjoin if reverse_direction: secondaryjoin = visitors.replacement_traverse( secondaryjoin, {}, col_to_bind ) lazywhere = sql.and_(lazywhere, secondaryjoin) bind_to_col = {binds[col].key: col for col in binds} return lazywhere, bind_to_col, equated_columns class _ColInAnnotations(object): """Serializable object that tests for a name in c._annotations.""" __slots__ = ("name",) def __init__(self, name): self.name = name def __call__(self, c): return self.name in c._annotations