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Edit File: interfaces.py
# orm/interfaces.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 """ Contains various base classes used throughout the ORM. Defines some key base classes prominent within the internals. This module and the classes within are mostly private, though some attributes are exposed when inspecting mappings. """ from __future__ import absolute_import import collections from . import exc as orm_exc from . import path_registry from .base import _MappedAttribute # noqa from .base import EXT_CONTINUE from .base import EXT_SKIP from .base import EXT_STOP from .base import InspectionAttr # noqa from .base import InspectionAttrInfo # noqa from .base import MANYTOMANY from .base import MANYTOONE from .base import NOT_EXTENSION from .base import ONETOMANY from .. import inspect from .. import inspection from .. import util from ..sql import operators from ..sql import roles from ..sql import visitors from ..sql.base import ExecutableOption from ..sql.traversals import HasCacheKey __all__ = ( "EXT_CONTINUE", "EXT_STOP", "EXT_SKIP", "ONETOMANY", "MANYTOMANY", "MANYTOONE", "NOT_EXTENSION", "LoaderStrategy", "MapperOption", "LoaderOption", "MapperProperty", "PropComparator", "StrategizedProperty", ) class ORMStatementRole(roles.StatementRole): _role_name = ( "Executable SQL or text() construct, including ORM " "aware objects" ) class ORMColumnsClauseRole(roles.ColumnsClauseRole): _role_name = "ORM mapped entity, aliased entity, or Column expression" class ORMEntityColumnsClauseRole(ORMColumnsClauseRole): _role_name = "ORM mapped or aliased entity" class ORMFromClauseRole(roles.StrictFromClauseRole): _role_name = "ORM mapped entity, aliased entity, or FROM expression" @inspection._self_inspects class MapperProperty( HasCacheKey, _MappedAttribute, InspectionAttr, util.MemoizedSlots ): """Represent a particular class attribute mapped by :class:`_orm.Mapper`. The most common occurrences of :class:`.MapperProperty` are the mapped :class:`_schema.Column`, which is represented in a mapping as an instance of :class:`.ColumnProperty`, and a reference to another class produced by :func:`_orm.relationship`, represented in the mapping as an instance of :class:`.RelationshipProperty`. """ __slots__ = ( "_configure_started", "_configure_finished", "parent", "key", "info", ) _cache_key_traversal = [ ("parent", visitors.ExtendedInternalTraversal.dp_has_cache_key), ("key", visitors.ExtendedInternalTraversal.dp_string), ] cascade = frozenset() """The set of 'cascade' attribute names. This collection is checked before the 'cascade_iterator' method is called. The collection typically only applies to a RelationshipProperty. """ is_property = True """Part of the InspectionAttr interface; states this object is a mapper property. """ @property def _links_to_entity(self): """True if this MapperProperty refers to a mapped entity. Should only be True for RelationshipProperty, False for all others. """ raise NotImplementedError() def _memoized_attr_info(self): """Info dictionary associated with the object, allowing user-defined data to be associated with this :class:`.InspectionAttr`. The dictionary is generated when first accessed. Alternatively, it can be specified as a constructor argument to the :func:`.column_property`, :func:`_orm.relationship`, or :func:`.composite` functions. .. versionchanged:: 1.0.0 :attr:`.MapperProperty.info` is also available on extension types via the :attr:`.InspectionAttrInfo.info` attribute, so that it can apply to a wider variety of ORM and extension constructs. .. seealso:: :attr:`.QueryableAttribute.info` :attr:`.SchemaItem.info` """ return {} def setup(self, context, query_entity, path, adapter, **kwargs): """Called by Query for the purposes of constructing a SQL statement. Each MapperProperty associated with the target mapper processes the statement referenced by the query context, adding columns and/or criterion as appropriate. """ def create_row_processor( self, context, query_entity, path, mapper, result, adapter, populators ): """Produce row processing functions and append to the given set of populators lists. """ def cascade_iterator( self, type_, state, dict_, visited_states, halt_on=None ): """Iterate through instances related to the given instance for a particular 'cascade', starting with this MapperProperty. Return an iterator3-tuples (instance, mapper, state). Note that the 'cascade' collection on this MapperProperty is checked first for the given type before cascade_iterator is called. This method typically only applies to RelationshipProperty. """ return iter(()) def set_parent(self, parent, init): """Set the parent mapper that references this MapperProperty. This method is overridden by some subclasses to perform extra setup when the mapper is first known. """ self.parent = parent def instrument_class(self, mapper): """Hook called by the Mapper to the property to initiate instrumentation of the class attribute managed by this MapperProperty. The MapperProperty here will typically call out to the attributes module to set up an InstrumentedAttribute. This step is the first of two steps to set up an InstrumentedAttribute, and is called early in the mapper setup process. The second step is typically the init_class_attribute step, called from StrategizedProperty via the post_instrument_class() hook. This step assigns additional state to the InstrumentedAttribute (specifically the "impl") which has been determined after the MapperProperty has determined what kind of persistence management it needs to do (e.g. scalar, object, collection, etc). """ def __init__(self): self._configure_started = False self._configure_finished = False def init(self): """Called after all mappers are created to assemble relationships between mappers and perform other post-mapper-creation initialization steps. """ self._configure_started = True self.do_init() self._configure_finished = True @property def class_attribute(self): """Return the class-bound descriptor corresponding to this :class:`.MapperProperty`. This is basically a ``getattr()`` call:: return getattr(self.parent.class_, self.key) I.e. if this :class:`.MapperProperty` were named ``addresses``, and the class to which it is mapped is ``User``, this sequence is possible:: >>> from sqlalchemy import inspect >>> mapper = inspect(User) >>> addresses_property = mapper.attrs.addresses >>> addresses_property.class_attribute is User.addresses True >>> User.addresses.property is addresses_property True """ return getattr(self.parent.class_, self.key) def do_init(self): """Perform subclass-specific initialization post-mapper-creation steps. This is a template method called by the ``MapperProperty`` object's init() method. """ def post_instrument_class(self, mapper): """Perform instrumentation adjustments that need to occur after init() has completed. The given Mapper is the Mapper invoking the operation, which may not be the same Mapper as self.parent in an inheritance scenario; however, Mapper will always at least be a sub-mapper of self.parent. This method is typically used by StrategizedProperty, which delegates it to LoaderStrategy.init_class_attribute() to perform final setup on the class-bound InstrumentedAttribute. """ def merge( self, session, source_state, source_dict, dest_state, dest_dict, load, _recursive, _resolve_conflict_map, ): """Merge the attribute represented by this ``MapperProperty`` from source to destination object. """ def __repr__(self): return "<%s at 0x%x; %s>" % ( self.__class__.__name__, id(self), getattr(self, "key", "no key"), ) @inspection._self_inspects class PropComparator(operators.ColumnOperators): r"""Defines SQL operators for :class:`.MapperProperty` objects. SQLAlchemy allows for operators to be redefined at both the Core and ORM level. :class:`.PropComparator` is the base class of operator redefinition for ORM-level operations, including those of :class:`.ColumnProperty`, :class:`.RelationshipProperty`, and :class:`.CompositeProperty`. .. note:: With the advent of Hybrid properties introduced in SQLAlchemy 0.7, as well as Core-level operator redefinition in SQLAlchemy 0.8, the use case for user-defined :class:`.PropComparator` instances is extremely rare. See :ref:`hybrids_toplevel` as well as :ref:`types_operators`. User-defined subclasses of :class:`.PropComparator` may be created. The built-in Python comparison and math operator methods, such as :meth:`.operators.ColumnOperators.__eq__`, :meth:`.operators.ColumnOperators.__lt__`, and :meth:`.operators.ColumnOperators.__add__`, can be overridden to provide new operator behavior. The custom :class:`.PropComparator` is passed to the :class:`.MapperProperty` instance via the ``comparator_factory`` argument. In each case, the appropriate subclass of :class:`.PropComparator` should be used:: # definition of custom PropComparator subclasses from sqlalchemy.orm.properties import \ ColumnProperty,\ CompositeProperty,\ RelationshipProperty class MyColumnComparator(ColumnProperty.Comparator): def __eq__(self, other): return self.__clause_element__() == other class MyRelationshipComparator(RelationshipProperty.Comparator): def any(self, expression): "define the 'any' operation" # ... class MyCompositeComparator(CompositeProperty.Comparator): def __gt__(self, other): "redefine the 'greater than' operation" return sql.and_(*[a>b for a, b in zip(self.__clause_element__().clauses, other.__composite_values__())]) # application of custom PropComparator subclasses from sqlalchemy.orm import column_property, relationship, composite from sqlalchemy import Column, String class SomeMappedClass(Base): some_column = column_property(Column("some_column", String), comparator_factory=MyColumnComparator) some_relationship = relationship(SomeOtherClass, comparator_factory=MyRelationshipComparator) some_composite = composite( Column("a", String), Column("b", String), comparator_factory=MyCompositeComparator ) Note that for column-level operator redefinition, it's usually simpler to define the operators at the Core level, using the :attr:`.TypeEngine.comparator_factory` attribute. See :ref:`types_operators` for more detail. .. seealso:: :class:`.ColumnProperty.Comparator` :class:`.RelationshipProperty.Comparator` :class:`.CompositeProperty.Comparator` :class:`.ColumnOperators` :ref:`types_operators` :attr:`.TypeEngine.comparator_factory` """ __slots__ = "prop", "property", "_parententity", "_adapt_to_entity" __visit_name__ = "orm_prop_comparator" def __init__( self, prop, parentmapper, adapt_to_entity=None, ): self.prop = self.property = prop self._parententity = adapt_to_entity or parentmapper self._adapt_to_entity = adapt_to_entity def __clause_element__(self): raise NotImplementedError("%r" % self) def _bulk_update_tuples(self, value): """Receive a SQL expression that represents a value in the SET clause of an UPDATE statement. Return a tuple that can be passed to a :class:`_expression.Update` construct. """ return [(self.__clause_element__(), value)] def adapt_to_entity(self, adapt_to_entity): """Return a copy of this PropComparator which will use the given :class:`.AliasedInsp` to produce corresponding expressions. """ return self.__class__(self.prop, self._parententity, adapt_to_entity) @property def _parentmapper(self): """legacy; this is renamed to _parententity to be compatible with QueryableAttribute.""" return inspect(self._parententity).mapper @property def _propagate_attrs(self): # this suits the case in coercions where we don't actually # call ``__clause_element__()`` but still need to get # resolved._propagate_attrs. See #6558. return util.immutabledict( { "compile_state_plugin": "orm", "plugin_subject": self._parentmapper, } ) @property def adapter(self): """Produce a callable that adapts column expressions to suit an aliased version of this comparator. """ if self._adapt_to_entity is None: return None else: return self._adapt_to_entity._adapt_element @property def info(self): return self.property.info @staticmethod def any_op(a, b, **kwargs): return a.any(b, **kwargs) @staticmethod def has_op(a, b, **kwargs): return a.has(b, **kwargs) @staticmethod def of_type_op(a, class_): return a.of_type(class_) def of_type(self, class_): r"""Redefine this object in terms of a polymorphic subclass, :func:`_orm.with_polymorphic` construct, or :func:`_orm.aliased` construct. Returns a new PropComparator from which further criterion can be evaluated. e.g.:: query.join(Company.employees.of_type(Engineer)).\ filter(Engineer.name=='foo') :param \class_: a class or mapper indicating that criterion will be against this specific subclass. .. seealso:: :ref:`queryguide_join_onclause` - in the :ref:`queryguide_toplevel` :ref:`inheritance_of_type` """ return self.operate(PropComparator.of_type_op, class_) def and_(self, *criteria): """Add additional criteria to the ON clause that's represented by this relationship attribute. E.g.:: stmt = select(User).join( User.addresses.and_(Address.email_address != 'foo') ) stmt = select(User).options( joinedload(User.addresses.and_(Address.email_address != 'foo')) ) .. versionadded:: 1.4 .. seealso:: :ref:`orm_queryguide_join_on_augmented` :ref:`loader_option_criteria` :func:`.with_loader_criteria` """ return self.operate(operators.and_, *criteria) def any(self, criterion=None, **kwargs): r"""Return true if this collection contains any member that meets the given criterion. The usual implementation of ``any()`` is :meth:`.RelationshipProperty.Comparator.any`. :param criterion: an optional ClauseElement formulated against the member class' table or attributes. :param \**kwargs: key/value pairs corresponding to member class attribute names which will be compared via equality to the corresponding values. """ return self.operate(PropComparator.any_op, criterion, **kwargs) def has(self, criterion=None, **kwargs): r"""Return true if this element references a member which meets the given criterion. The usual implementation of ``has()`` is :meth:`.RelationshipProperty.Comparator.has`. :param criterion: an optional ClauseElement formulated against the member class' table or attributes. :param \**kwargs: key/value pairs corresponding to member class attribute names which will be compared via equality to the corresponding values. """ return self.operate(PropComparator.has_op, criterion, **kwargs) class StrategizedProperty(MapperProperty): """A MapperProperty which uses selectable strategies to affect loading behavior. There is a single strategy selected by default. Alternate strategies can be selected at Query time through the usage of ``StrategizedOption`` objects via the Query.options() method. The mechanics of StrategizedProperty are used for every Query invocation for every mapped attribute participating in that Query, to determine first how the attribute will be rendered in SQL and secondly how the attribute will retrieve a value from a result row and apply it to a mapped object. The routines here are very performance-critical. """ __slots__ = ( "_strategies", "strategy", "_wildcard_token", "_default_path_loader_key", ) inherit_cache = True strategy_wildcard_key = None def _memoized_attr__wildcard_token(self): return ( "%s:%s" % (self.strategy_wildcard_key, path_registry._WILDCARD_TOKEN), ) def _memoized_attr__default_path_loader_key(self): return ( "loader", ( "%s:%s" % (self.strategy_wildcard_key, path_registry._DEFAULT_TOKEN), ), ) def _get_context_loader(self, context, path): load = None search_path = path[self] # search among: exact match, "attr.*", "default" strategy # if any. for path_key in ( search_path._loader_key, search_path._wildcard_path_loader_key, search_path._default_path_loader_key, ): if path_key in context.attributes: load = context.attributes[path_key] break return load def _get_strategy(self, key): try: return self._strategies[key] except KeyError: pass # run outside to prevent transfer of exception context cls = self._strategy_lookup(self, *key) # this previously was setting self._strategies[cls], that's # a bad idea; should use strategy key at all times because every # strategy has multiple keys at this point self._strategies[key] = strategy = cls(self, key) return strategy def setup(self, context, query_entity, path, adapter, **kwargs): loader = self._get_context_loader(context, path) if loader and loader.strategy: strat = self._get_strategy(loader.strategy) else: strat = self.strategy strat.setup_query( context, query_entity, path, loader, adapter, **kwargs ) def create_row_processor( self, context, query_entity, path, mapper, result, adapter, populators ): loader = self._get_context_loader(context, path) if loader and loader.strategy: strat = self._get_strategy(loader.strategy) else: strat = self.strategy strat.create_row_processor( context, query_entity, path, loader, mapper, result, adapter, populators, ) def do_init(self): self._strategies = {} self.strategy = self._get_strategy(self.strategy_key) def post_instrument_class(self, mapper): if ( not self.parent.non_primary and not mapper.class_manager._attr_has_impl(self.key) ): self.strategy.init_class_attribute(mapper) _all_strategies = collections.defaultdict(dict) @classmethod def strategy_for(cls, **kw): def decorate(dec_cls): # ensure each subclass of the strategy has its # own _strategy_keys collection if "_strategy_keys" not in dec_cls.__dict__: dec_cls._strategy_keys = [] key = tuple(sorted(kw.items())) cls._all_strategies[cls][key] = dec_cls dec_cls._strategy_keys.append(key) return dec_cls return decorate @classmethod def _strategy_lookup(cls, requesting_property, *key): requesting_property.parent._with_polymorphic_mappers for prop_cls in cls.__mro__: if prop_cls in cls._all_strategies: strategies = cls._all_strategies[prop_cls] try: return strategies[key] except KeyError: pass for property_type, strats in cls._all_strategies.items(): if key in strats: intended_property_type = property_type actual_strategy = strats[key] break else: intended_property_type = None actual_strategy = None raise orm_exc.LoaderStrategyException( cls, requesting_property, intended_property_type, actual_strategy, key, ) class ORMOption(ExecutableOption): """Base class for option objects that are passed to ORM queries. These options may be consumed by :meth:`.Query.options`, :meth:`.Select.options`, or in a more general sense by any :meth:`.Executable.options` method. They are interpreted at statement compile time or execution time in modern use. The deprecated :class:`.MapperOption` is consumed at ORM query construction time. .. versionadded:: 1.4 """ __slots__ = () _is_legacy_option = False propagate_to_loaders = False """if True, indicate this option should be carried along to "secondary" SELECT statements that occur for relationship lazy loaders as well as attribute load / refresh operations. """ _is_compile_state = False _is_criteria_option = False _is_strategy_option = False def _adapt_cached_option_to_uncached_option(self, context, uncached_opt): """given "self" which is an option from a cached query, as well as the corresponding option from the uncached version of the same query, return the option we should use in a new query, in the context of a loader strategy being asked to load related rows on behalf of that cached query, which is assumed to be building a new query based on entities passed to us from the cached query. Currently this routine chooses between "self" and "uncached" without manufacturing anything new. If the option is itself a loader strategy option which has a path, that path needs to match to the entities being passed to us by the cached query, so the :class:`_orm.Load` subclass overrides this to return "self". For all other options, we return the uncached form which may have changing state, such as a with_loader_criteria() option which will very often have new state. This routine could in the future involve generating a new option based on both inputs if use cases arise, such as if with_loader_criteria() needed to match up to ``AliasedClass`` instances given in the parent query. However, longer term it might be better to restructure things such that ``AliasedClass`` entities are always matched up on their cache key, instead of identity, in things like paths and such, so that this whole issue of "the uncached option does not match the entities" goes away. However this would make ``PathRegistry`` more complicated and difficult to debug as well as potentially less performant in that it would be hashing enormous cache keys rather than a simple AliasedInsp. UNLESS, we could get cache keys overall to be reliably hashed into something like an md5 key. .. versionadded:: 1.4.41 """ if uncached_opt is not None: return uncached_opt else: return self class CompileStateOption(HasCacheKey, ORMOption): """base for :class:`.ORMOption` classes that affect the compilation of a SQL query and therefore need to be part of the cache key. .. note:: :class:`.CompileStateOption` is generally non-public and should not be used as a base class for user-defined options; instead, use :class:`.UserDefinedOption`, which is easier to use as it does not interact with ORM compilation internals or caching. :class:`.CompileStateOption` defines an internal attribute ``_is_compile_state=True`` which has the effect of the ORM compilation routines for SELECT and other statements will call upon these options when a SQL string is being compiled. As such, these classes implement :class:`.HasCacheKey` and need to provide robust ``_cache_key_traversal`` structures. The :class:`.CompileStateOption` class is used to implement the ORM :class:`.LoaderOption` and :class:`.CriteriaOption` classes. .. versionadded:: 1.4.28 """ _is_compile_state = True def process_compile_state(self, compile_state): """Apply a modification to a given :class:`.CompileState`.""" def process_compile_state_replaced_entities( self, compile_state, mapper_entities ): """Apply a modification to a given :class:`.CompileState`, given entities that were replaced by with_only_columns() or with_entities(). .. versionadded:: 1.4.19 """ class LoaderOption(CompileStateOption): """Describe a loader modification to an ORM statement at compilation time. .. versionadded:: 1.4 """ def process_compile_state_replaced_entities( self, compile_state, mapper_entities ): """Apply a modification to a given :class:`.CompileState`, given entities that were replaced by with_only_columns() or with_entities(). .. versionadded:: 1.4.19 """ self.process_compile_state(compile_state) def process_compile_state(self, compile_state): """Apply a modification to a given :class:`.CompileState`.""" class CriteriaOption(CompileStateOption): """Describe a WHERE criteria modification to an ORM statement at compilation time. .. versionadded:: 1.4 """ _is_criteria_option = True def process_compile_state(self, compile_state): """Apply a modification to a given :class:`.CompileState`.""" def get_global_criteria(self, attributes): """update additional entity criteria options in the given attributes dictionary. """ class UserDefinedOption(ORMOption): """Base class for a user-defined option that can be consumed from the :meth:`.SessionEvents.do_orm_execute` event hook. """ _is_legacy_option = False propagate_to_loaders = False """if True, indicate this option should be carried along to "secondary" Query objects produced during lazy loads or refresh operations. """ def __init__(self, payload=None): self.payload = payload @util.deprecated_cls( "1.4", "The :class:`.MapperOption class is deprecated and will be removed " "in a future release. For " "modifications to queries on a per-execution basis, use the " ":class:`.UserDefinedOption` class to establish state within a " ":class:`.Query` or other Core statement, then use the " ":meth:`.SessionEvents.before_orm_execute` hook to consume them.", constructor=None, ) class MapperOption(ORMOption): """Describe a modification to a Query""" _is_legacy_option = True propagate_to_loaders = False """if True, indicate this option should be carried along to "secondary" Query objects produced during lazy loads or refresh operations. """ def process_query(self, query): """Apply a modification to the given :class:`_query.Query`.""" def process_query_conditionally(self, query): """same as process_query(), except that this option may not apply to the given query. This is typically applied during a lazy load or scalar refresh operation to propagate options stated in the original Query to the new Query being used for the load. It occurs for those options that specify propagate_to_loaders=True. """ self.process_query(query) class LoaderStrategy(object): """Describe the loading behavior of a StrategizedProperty object. The ``LoaderStrategy`` interacts with the querying process in three ways: * it controls the configuration of the ``InstrumentedAttribute`` placed on a class to handle the behavior of the attribute. this may involve setting up class-level callable functions to fire off a select operation when the attribute is first accessed (i.e. a lazy load) * it processes the ``QueryContext`` at statement construction time, where it can modify the SQL statement that is being produced. For example, simple column attributes will add their represented column to the list of selected columns, a joined eager loader may establish join clauses to add to the statement. * It produces "row processor" functions at result fetching time. These "row processor" functions populate a particular attribute on a particular mapped instance. """ __slots__ = ( "parent_property", "is_class_level", "parent", "key", "strategy_key", "strategy_opts", ) def __init__(self, parent, strategy_key): self.parent_property = parent self.is_class_level = False self.parent = self.parent_property.parent self.key = self.parent_property.key self.strategy_key = strategy_key self.strategy_opts = dict(strategy_key) def init_class_attribute(self, mapper): pass def setup_query( self, compile_state, query_entity, path, loadopt, adapter, **kwargs ): """Establish column and other state for a given QueryContext. This method fulfills the contract specified by MapperProperty.setup(). StrategizedProperty delegates its setup() method directly to this method. """ def create_row_processor( self, context, query_entity, path, loadopt, mapper, result, adapter, populators, ): """Establish row processing functions for a given QueryContext. This method fulfills the contract specified by MapperProperty.create_row_processor(). StrategizedProperty delegates its create_row_processor() method directly to this method. """ def __str__(self): return str(self.parent_property)