# orm/query.py # Copyright (C) 2005-2019 the SQLAlchemy authors and contributors # # # This module is part of SQLAlchemy and is released under # the MIT License: http://www.opensource.org/licenses/mit-license.php """The Query class and support. Defines the :class:`.Query` class, the central construct used by the ORM to construct database queries. The :class:`.Query` class should not be confused with the :class:`.Select` class, which defines database SELECT operations at the SQL (non-ORM) level. ``Query`` differs from ``Select`` in that it returns ORM-mapped objects and interacts with an ORM session, whereas the ``Select`` construct interacts directly with the database to return iterable result sets. """ from itertools import chain from . import attributes from . import exc as orm_exc from . import interfaces from . import loading from . import persistence from . import properties from .base import _entity_descriptor from .base import _generative from .base import _is_aliased_class from .base import _is_mapped_class from .base import _orm_columns from .base import InspectionAttr from .path_registry import PathRegistry from .util import _entity_corresponds_to from .util import aliased from .util import AliasedClass from .util import join as orm_join from .util import object_mapper from .util import ORMAdapter from .util import with_parent from .. import exc as sa_exc from .. import inspect from .. import inspection from .. import log from .. import sql from .. import util from ..sql import expression from ..sql import util as sql_util from ..sql import visitors from ..sql.base import ColumnCollection from ..sql.expression import _interpret_as_from from ..sql.selectable import ForUpdateArg __all__ = ["Query", "QueryContext", "aliased"] _path_registry = PathRegistry.root @inspection._self_inspects @log.class_logger class Query(object): """ORM-level SQL construction object. :class:`.Query` is the source of all SELECT statements generated by the ORM, both those formulated by end-user query operations as well as by high level internal operations such as related collection loading. It features a generative interface whereby successive calls return a new :class:`.Query` object, a copy of the former with additional criteria and options associated with it. :class:`.Query` objects are normally initially generated using the :meth:`~.Session.query` method of :class:`.Session`, and in less common cases by instantiating the :class:`.Query` directly and associating with a :class:`.Session` using the :meth:`.Query.with_session` method. For a full walkthrough of :class:`.Query` usage, see the :ref:`ormtutorial_toplevel`. """ _only_return_tuples = False _enable_eagerloads = True _enable_assertions = True _with_labels = False _criterion = None _yield_per = None _order_by = False _group_by = False _having = None _distinct = False _prefixes = None _suffixes = None _offset = None _limit = None _for_update_arg = None _statement = None _correlate = frozenset() _populate_existing = False _invoke_all_eagers = True _version_check = False _autoflush = True _only_load_props = None _refresh_state = None _refresh_identity_token = None _from_obj = () _join_entities = () _select_from_entity = None _mapper_adapter_map = {} _filter_aliases = () _from_obj_alias = None _joinpath = _joinpoint = util.immutabledict() _execution_options = util.immutabledict() _params = util.immutabledict() _attributes = util.immutabledict() _with_options = () _with_hints = () _enable_single_crit = True _orm_only_adapt = True _orm_only_from_obj_alias = True _current_path = _path_registry _has_mapper_entities = False lazy_loaded_from = None """An :class:`.InstanceState` that is using this :class:`.Query` for a lazy load operation. This can be used for extensions like the horizontal sharding extension as well as event handlers and custom mapper options to determine when a query is being used to lazy load a relationship on an object. .. versionadded:: 1.2.9 """ def __init__(self, entities, session=None): """Construct a :class:`.Query` directly. E.g.:: q = Query([User, Address], session=some_session) The above is equivalent to:: q = some_session.query(User, Address) :param entities: a sequence of entities and/or SQL expressions. :param session: a :class:`.Session` with which the :class:`.Query` will be associated. Optional; a :class:`.Query` can be associated with a :class:`.Session` generatively via the :meth:`.Query.with_session` method as well. .. seealso:: :meth:`.Session.query` :meth:`.Query.with_session` """ self.session = session self._polymorphic_adapters = {} self._set_entities(entities) def _set_entities(self, entities, entity_wrapper=None): if entity_wrapper is None: entity_wrapper = _QueryEntity self._entities = [] self._primary_entity = None self._has_mapper_entities = False # 1. don't run util.to_list() or _set_entity_selectables # if no entities were passed - major performance bottleneck # from lazy loader implementation when it seeks to use Query # class for an identity lookup, causes test_orm.py to fail # with thousands of extra function calls, see issue #4228 # for why this use had to be added # 2. can't use classmethod on Query because session.query_cls # is an arbitrary callable in some user recipes, not # necessarily a class, so we don't have the class available. # see issue #4256 # 3. can't do "if entities is not None" because we usually get here # from session.query() which takes in *entities. # 4. can't do "if entities" because users make use of undocumented # to_list() behavior here and they pass clause expressions that # can't be evaluated as boolean. See issue #4269. # 5. the empty tuple is a singleton in cPython, take advantage of this # so that we can skip for the empty "*entities" case without using # any Python overloadable operators. # if entities is not (): for ent in util.to_list(entities): entity_wrapper(self, ent) self._set_entity_selectables(self._entities) def _set_entity_selectables(self, entities): self._mapper_adapter_map = d = self._mapper_adapter_map.copy() for ent in entities: for entity in ent.entities: if entity not in d: ext_info = inspect(entity) if ( not ext_info.is_aliased_class and ext_info.mapper.with_polymorphic ): if ( ext_info.mapper.persist_selectable not in self._polymorphic_adapters ): self._mapper_loads_polymorphically_with( ext_info.mapper, sql_util.ColumnAdapter( ext_info.selectable, ext_info.mapper._equivalent_columns, ), ) aliased_adapter = None elif ext_info.is_aliased_class: aliased_adapter = ext_info._adapter else: aliased_adapter = None d[entity] = (ext_info, aliased_adapter) ent.setup_entity(*d[entity]) def _mapper_loads_polymorphically_with(self, mapper, adapter): for m2 in mapper._with_polymorphic_mappers or [mapper]: self._polymorphic_adapters[m2] = adapter for m in m2.iterate_to_root(): self._polymorphic_adapters[m.local_table] = adapter def _set_select_from(self, obj, set_base_alias): fa = [] select_from_alias = None for from_obj in obj: info = inspect(from_obj) if hasattr(info, "mapper") and ( info.is_mapper or info.is_aliased_class ): self._select_from_entity = info if set_base_alias and not info.is_aliased_class: raise sa_exc.ArgumentError( "A selectable (FromClause) instance is " "expected when the base alias is being set." ) fa.append(info.selectable) elif not info.is_selectable: raise sa_exc.ArgumentError( "argument is not a mapped class, mapper, " "aliased(), or FromClause instance." ) else: if isinstance(from_obj, expression.SelectBase): from_obj = from_obj.alias() if set_base_alias: select_from_alias = from_obj fa.append(from_obj) self._from_obj = tuple(fa) if ( set_base_alias and len(self._from_obj) == 1 and isinstance(select_from_alias, expression.Alias) ): equivs = self.__all_equivs() self._from_obj_alias = sql_util.ColumnAdapter( self._from_obj[0], equivs ) elif ( set_base_alias and len(self._from_obj) == 1 and hasattr(info, "mapper") and info.is_aliased_class ): self._from_obj_alias = info._adapter def _reset_polymorphic_adapter(self, mapper): for m2 in mapper._with_polymorphic_mappers: self._polymorphic_adapters.pop(m2, None) for m in m2.iterate_to_root(): self._polymorphic_adapters.pop(m.local_table, None) def _adapt_polymorphic_element(self, element): if "parententity" in element._annotations: search = element._annotations["parententity"] alias = self._polymorphic_adapters.get(search, None) if alias: return alias.adapt_clause(element) if isinstance(element, expression.FromClause): search = element elif hasattr(element, "table"): search = element.table else: return None alias = self._polymorphic_adapters.get(search, None) if alias: return alias.adapt_clause(element) def _adapt_col_list(self, cols): return [ self._adapt_clause( expression._literal_as_label_reference(o), True, True ) for o in cols ] @_generative() def _set_lazyload_from(self, state): self.lazy_loaded_from = state @_generative() def _adapt_all_clauses(self): self._orm_only_adapt = False def _adapt_clause(self, clause, as_filter, orm_only): """Adapt incoming clauses to transformations which have been applied within this query.""" adapters = [] # do we adapt all expression elements or only those # tagged as 'ORM' constructs ? if not self._orm_only_adapt: orm_only = False if as_filter and self._filter_aliases: for fa in self._filter_aliases: adapters.append((orm_only, fa.replace)) if self._from_obj_alias: # for the "from obj" alias, apply extra rule to the # 'ORM only' check, if this query were generated from a # subquery of itself, i.e. _from_selectable(), apply adaption # to all SQL constructs. adapters.append( ( orm_only if self._orm_only_from_obj_alias else False, self._from_obj_alias.replace, ) ) if self._polymorphic_adapters: adapters.append((orm_only, self._adapt_polymorphic_element)) if not adapters: return clause def replace(elem): is_orm_adapt = ( "_orm_adapt" in elem._annotations or "parententity" in elem._annotations ) for _orm_only, adapter in adapters: if not _orm_only or is_orm_adapt: e = adapter(elem) if e is not None: return e return visitors.replacement_traverse(clause, {}, replace) def _query_entity_zero(self): """Return the first QueryEntity.""" return self._entities[0] def _mapper_zero(self): """return the Mapper associated with the first QueryEntity.""" return self._entities[0].mapper def _entity_zero(self): """Return the 'entity' (mapper or AliasedClass) associated with the first QueryEntity, or alternatively the 'select from' entity if specified.""" return ( self._select_from_entity if self._select_from_entity is not None else self._query_entity_zero().entity_zero ) @property def _mapper_entities(self): for ent in self._entities: if isinstance(ent, _MapperEntity): yield ent def _joinpoint_zero(self): return self._joinpoint.get("_joinpoint_entity", self._entity_zero()) def _bind_mapper(self): ezero = self._entity_zero() if ezero is not None: insp = inspect(ezero) if not insp.is_clause_element: return insp.mapper return None def _only_full_mapper_zero(self, methname): if self._entities != [self._primary_entity]: raise sa_exc.InvalidRequestError( "%s() can only be used against " "a single mapped class." % methname ) return self._primary_entity.entity_zero def _only_entity_zero(self, rationale=None): if len(self._entities) > 1: raise sa_exc.InvalidRequestError( rationale or "This operation requires a Query " "against a single mapper." ) return self._entity_zero() def __all_equivs(self): equivs = {} for ent in self._mapper_entities: equivs.update(ent.mapper._equivalent_columns) return equivs def _get_condition(self): return self._no_criterion_condition( "get", order_by=False, distinct=False ) def _get_existing_condition(self): self._no_criterion_assertion("get", order_by=False, distinct=False) def _no_criterion_assertion(self, meth, order_by=True, distinct=True): if not self._enable_assertions: return if ( self._criterion is not None or self._statement is not None or self._from_obj or self._limit is not None or self._offset is not None or self._group_by or (order_by and self._order_by) or (distinct and self._distinct) ): raise sa_exc.InvalidRequestError( "Query.%s() being called on a " "Query with existing criterion. " % meth ) def _no_criterion_condition(self, meth, order_by=True, distinct=True): self._no_criterion_assertion(meth, order_by, distinct) self._from_obj = () self._statement = self._criterion = None self._order_by = self._group_by = self._distinct = False def _no_clauseelement_condition(self, meth): if not self._enable_assertions: return if self._order_by: raise sa_exc.InvalidRequestError( "Query.%s() being called on a " "Query with existing criterion. " % meth ) self._no_criterion_condition(meth) def _no_statement_condition(self, meth): if not self._enable_assertions: return if self._statement is not None: raise sa_exc.InvalidRequestError( ( "Query.%s() being called on a Query with an existing full " "statement - can't apply criterion." ) % meth ) def _no_limit_offset(self, meth): if not self._enable_assertions: return if self._limit is not None or self._offset is not None: raise sa_exc.InvalidRequestError( "Query.%s() being called on a Query which already has LIMIT " "or OFFSET applied. To modify the row-limited results of a " " Query, call from_self() first. " "Otherwise, call %s() before limit() or offset() " "are applied." % (meth, meth) ) def _get_options( self, populate_existing=None, version_check=None, only_load_props=None, refresh_state=None, identity_token=None, ): if populate_existing: self._populate_existing = populate_existing if version_check: self._version_check = version_check if refresh_state: self._refresh_state = refresh_state if only_load_props: self._only_load_props = set(only_load_props) if identity_token: self._refresh_identity_token = identity_token return self def _clone(self): cls = self.__class__ q = cls.__new__(cls) q.__dict__ = self.__dict__.copy() return q @property def statement(self): """The full SELECT statement represented by this Query. The statement by default will not have disambiguating labels applied to the construct unless with_labels(True) is called first. """ stmt = self._compile_context(labels=self._with_labels).statement if self._params: stmt = stmt.params(self._params) return stmt def subquery(self, name=None, with_labels=False, reduce_columns=False): """return the full SELECT statement represented by this :class:`.Query`, embedded within an :class:`.Alias`. Eager JOIN generation within the query is disabled. :param name: string name to be assigned as the alias; this is passed through to :meth:`.FromClause.alias`. If ``None``, a name will be deterministically generated at compile time. :param with_labels: if True, :meth:`.with_labels` will be called on the :class:`.Query` first to apply table-qualified labels to all columns. :param reduce_columns: if True, :meth:`.Select.reduce_columns` will be called on the resulting :func:`.select` construct, to remove same-named columns where one also refers to the other via foreign key or WHERE clause equivalence. """ q = self.enable_eagerloads(False) if with_labels: q = q.with_labels() q = q.statement if reduce_columns: q = q.reduce_columns() return q.alias(name=name) def cte(self, name=None, recursive=False): r"""Return the full SELECT statement represented by this :class:`.Query` represented as a common table expression (CTE). Parameters and usage are the same as those of the :meth:`.SelectBase.cte` method; see that method for further details. Here is the `PostgreSQL WITH RECURSIVE example `_. Note that, in this example, the ``included_parts`` cte and the ``incl_alias`` alias of it are Core selectables, which means the columns are accessed via the ``.c.`` attribute. The ``parts_alias`` object is an :func:`.orm.aliased` instance of the ``Part`` entity, so column-mapped attributes are available directly:: from sqlalchemy.orm import aliased class Part(Base): __tablename__ = 'part' part = Column(String, primary_key=True) sub_part = Column(String, primary_key=True) quantity = Column(Integer) included_parts = session.query( Part.sub_part, Part.part, Part.quantity).\ filter(Part.part=="our part").\ cte(name="included_parts", recursive=True) incl_alias = aliased(included_parts, name="pr") parts_alias = aliased(Part, name="p") included_parts = included_parts.union_all( session.query( parts_alias.sub_part, parts_alias.part, parts_alias.quantity).\ filter(parts_alias.part==incl_alias.c.sub_part) ) q = session.query( included_parts.c.sub_part, func.sum(included_parts.c.quantity). label('total_quantity') ).\ group_by(included_parts.c.sub_part) .. seealso:: :meth:`.HasCTE.cte` """ return self.enable_eagerloads(False).statement.cte( name=name, recursive=recursive ) def label(self, name): """Return the full SELECT statement represented by this :class:`.Query`, converted to a scalar subquery with a label of the given name. Analogous to :meth:`sqlalchemy.sql.expression.SelectBase.label`. """ return self.enable_eagerloads(False).statement.label(name) def as_scalar(self): """Return the full SELECT statement represented by this :class:`.Query`, converted to a scalar subquery. Analogous to :meth:`sqlalchemy.sql.expression.SelectBase.as_scalar`. """ return self.enable_eagerloads(False).statement.as_scalar() @property def selectable(self): """Return the :class:`.Select` object emitted by this :class:`.Query`. Used for :func:`.inspect` compatibility, this is equivalent to:: query.enable_eagerloads(False).with_labels().statement """ return self.__clause_element__() def __clause_element__(self): return self.enable_eagerloads(False).with_labels().statement @_generative() def only_return_tuples(self, value): """When set to True, the query results will always be a tuple, specifically for single element queries. The default is False. . .. versionadded:: 1.2.5 """ self._only_return_tuples = value @_generative() def enable_eagerloads(self, value): """Control whether or not eager joins and subqueries are rendered. When set to False, the returned Query will not render eager joins regardless of :func:`~sqlalchemy.orm.joinedload`, :func:`~sqlalchemy.orm.subqueryload` options or mapper-level ``lazy='joined'``/``lazy='subquery'`` configurations. This is used primarily when nesting the Query's statement into a subquery or other selectable, or when using :meth:`.Query.yield_per`. """ self._enable_eagerloads = value def _no_yield_per(self, message): raise sa_exc.InvalidRequestError( "The yield_per Query option is currently not " "compatible with %s eager loading. Please " "specify lazyload('*') or query.enable_eagerloads(False) in " "order to " "proceed with query.yield_per()." % message ) @_generative() def with_labels(self): """Apply column labels to the return value of Query.statement. Indicates that this Query's `statement` accessor should return a SELECT statement that applies labels to all columns in the form _; this is commonly used to disambiguate columns from multiple tables which have the same name. When the `Query` actually issues SQL to load rows, it always uses column labeling. .. note:: The :meth:`.Query.with_labels` method *only* applies the output of :attr:`.Query.statement`, and *not* to any of the result-row invoking systems of :class:`.Query` itself, e.g. :meth:`.Query.first`, :meth:`.Query.all`, etc. To execute a query using :meth:`.Query.with_labels`, invoke the :attr:`.Query.statement` using :meth:`.Session.execute`:: result = session.execute(query.with_labels().statement) """ self._with_labels = True @_generative() def enable_assertions(self, value): """Control whether assertions are generated. When set to False, the returned Query will not assert its state before certain operations, including that LIMIT/OFFSET has not been applied when filter() is called, no criterion exists when get() is called, and no "from_statement()" exists when filter()/order_by()/group_by() etc. is called. This more permissive mode is used by custom Query subclasses to specify criterion or other modifiers outside of the usual usage patterns. Care should be taken to ensure that the usage pattern is even possible. A statement applied by from_statement() will override any criterion set by filter() or order_by(), for example. """ self._enable_assertions = value @property def whereclause(self): """A readonly attribute which returns the current WHERE criterion for this Query. This returned value is a SQL expression construct, or ``None`` if no criterion has been established. """ return self._criterion @_generative() def _with_current_path(self, path): """indicate that this query applies to objects loaded within a certain path. Used by deferred loaders (see strategies.py) which transfer query options from an originating query to a newly generated query intended for the deferred load. """ self._current_path = path @_generative(_no_clauseelement_condition) def with_polymorphic( self, cls_or_mappers, selectable=None, polymorphic_on=None ): """Load columns for inheriting classes. :meth:`.Query.with_polymorphic` applies transformations to the "main" mapped class represented by this :class:`.Query`. The "main" mapped class here means the :class:`.Query` object's first argument is a full class, i.e. ``session.query(SomeClass)``. These transformations allow additional tables to be present in the FROM clause so that columns for a joined-inheritance subclass are available in the query, both for the purposes of load-time efficiency as well as the ability to use these columns at query time. See the documentation section :ref:`with_polymorphic` for details on how this method is used. """ if not self._primary_entity: raise sa_exc.InvalidRequestError( "No primary mapper set up for this Query." ) entity = self._entities[0]._clone() self._entities = [entity] + self._entities[1:] entity.set_with_polymorphic( self, cls_or_mappers, selectable=selectable, polymorphic_on=polymorphic_on, ) @_generative() def yield_per(self, count): r"""Yield only ``count`` rows at a time. The purpose of this method is when fetching very large result sets (> 10K rows), to batch results in sub-collections and yield them out partially, so that the Python interpreter doesn't need to declare very large areas of memory which is both time consuming and leads to excessive memory use. The performance from fetching hundreds of thousands of rows can often double when a suitable yield-per setting (e.g. approximately 1000) is used, even with DBAPIs that buffer rows (which are most). The :meth:`.Query.yield_per` method **is not compatible subqueryload eager loading or joinedload eager loading when using collections**. It is potentially compatible with "select in" eager loading, **provided the database driver supports multiple, independent cursors** (pysqlite and psycopg2 are known to work, MySQL and SQL Server ODBC drivers do not). Therefore in some cases, it may be helpful to disable eager loads, either unconditionally with :meth:`.Query.enable_eagerloads`:: q = sess.query(Object).yield_per(100).enable_eagerloads(False) Or more selectively using :func:`.lazyload`; such as with an asterisk to specify the default loader scheme:: q = sess.query(Object).yield_per(100).\ options(lazyload('*'), joinedload(Object.some_related)) .. warning:: Use this method with caution; if the same instance is present in more than one batch of rows, end-user changes to attributes will be overwritten. In particular, it's usually impossible to use this setting with eagerly loaded collections (i.e. any lazy='joined' or 'subquery') since those collections will be cleared for a new load when encountered in a subsequent result batch. In the case of 'subquery' loading, the full result for all rows is fetched which generally defeats the purpose of :meth:`~sqlalchemy.orm.query.Query.yield_per`. Also note that while :meth:`~sqlalchemy.orm.query.Query.yield_per` will set the ``stream_results`` execution option to True, currently this is only understood by :mod:`~sqlalchemy.dialects.postgresql.psycopg2`, :mod:`~sqlalchemy.dialects.mysql.mysqldb` and :mod:`~sqlalchemy.dialects.mysql.pymysql` dialects which will stream results using server side cursors instead of pre-buffer all rows for this query. Other DBAPIs **pre-buffer all rows** before making them available. The memory use of raw database rows is much less than that of an ORM-mapped object, but should still be taken into consideration when benchmarking. .. seealso:: :meth:`.Query.enable_eagerloads` """ self._yield_per = count self._execution_options = self._execution_options.union( {"stream_results": True, "max_row_buffer": count} ) def get(self, ident): """Return an instance based on the given primary key identifier, or ``None`` if not found. E.g.:: my_user = session.query(User).get(5) some_object = session.query(VersionedFoo).get((5, 10)) some_object = session.query(VersionedFoo).get( {"id": 5, "version_id": 10}) :meth:`~.Query.get` is special in that it provides direct access to the identity map of the owning :class:`.Session`. If the given primary key identifier is present in the local identity map, the object is returned directly from this collection and no SQL is emitted, unless the object has been marked fully expired. If not present, a SELECT is performed in order to locate the object. :meth:`~.Query.get` also will perform a check if the object is present in the identity map and marked as expired - a SELECT is emitted to refresh the object as well as to ensure that the row is still present. If not, :class:`~sqlalchemy.orm.exc.ObjectDeletedError` is raised. :meth:`~.Query.get` is only used to return a single mapped instance, not multiple instances or individual column constructs, and strictly on a single primary key value. The originating :class:`.Query` must be constructed in this way, i.e. against a single mapped entity, with no additional filtering criterion. Loading options via :meth:`~.Query.options` may be applied however, and will be used if the object is not yet locally present. A lazy-loading, many-to-one attribute configured by :func:`.relationship`, using a simple foreign-key-to-primary-key criterion, will also use an operation equivalent to :meth:`~.Query.get` in order to retrieve the target value from the local identity map before querying the database. See :doc:`/orm/loading_relationships` for further details on relationship loading. :param ident: A scalar, tuple, or dictionary representing the primary key. For a composite (e.g. multiple column) primary key, a tuple or dictionary should be passed. For a single-column primary key, the scalar calling form is typically the most expedient. If the primary key of a row is the value "5", the call looks like:: my_object = query.get(5) The tuple form contains primary key values typically in the order in which they correspond to the mapped :class:`.Table` object's primary key columns, or if the :paramref:`.Mapper.primary_key` configuration parameter were used, in the order used for that parameter. For example, if the primary key of a row is represented by the integer digits "5, 10" the call would look like:: my_object = query.get((5, 10)) The dictionary form should include as keys the mapped attribute names corresponding to each element of the primary key. If the mapped class has the attributes ``id``, ``version_id`` as the attributes which store the object's primary key value, the call would look like:: my_object = query.get({"id": 5, "version_id": 10}) .. versionadded:: 1.3 the :meth:`.Query.get` method now optionally accepts a dictionary of attribute names to values in order to indicate a primary key identifier. :return: The object instance, or ``None``. """ return self._get_impl(ident, loading.load_on_pk_identity) def _identity_lookup( self, mapper, primary_key_identity, identity_token=None, passive=attributes.PASSIVE_OFF, lazy_loaded_from=None, ): """Locate an object in the identity map. Given a primary key identity, constructs an identity key and then looks in the session's identity map. If present, the object may be run through unexpiration rules (e.g. load unloaded attributes, check if was deleted). For performance reasons, while the :class:`.Query` must be instantiated, it may be instantiated with no entities, and the mapper is passed:: obj = session.query()._identity_lookup(inspect(SomeClass), (1, )) :param mapper: mapper in use :param primary_key_identity: the primary key we are searching for, as a tuple. :param identity_token: identity token that should be used to create the identity key. Used as is, however overriding subclasses can repurpose this in order to interpret the value in a special way, such as if None then look among multiple target tokens. :param passive: passive load flag passed to :func:`.loading.get_from_identity`, which impacts the behavior if the object is found; the object may be validated and/or unexpired if the flag allows for SQL to be emitted. :param lazy_loaded_from: an :class:`.InstanceState` that is specifically asking for this identity as a related identity. Used for sharding schemes where there is a correspondence between an object and a related object being lazy-loaded (or otherwise relationship-loaded). .. versionadded:: 1.2.9 :return: None if the object is not found in the identity map, *or* if the object was unexpired and found to have been deleted. if passive flags disallow SQL and the object is expired, returns PASSIVE_NO_RESULT. In all other cases the instance is returned. .. versionadded:: 1.2.7 """ key = mapper.identity_key_from_primary_key( primary_key_identity, identity_token=identity_token ) return loading.get_from_identity(self.session, key, passive) def _get_impl(self, primary_key_identity, db_load_fn, identity_token=None): # convert composite types to individual args if hasattr(primary_key_identity, "__composite_values__"): primary_key_identity = primary_key_identity.__composite_values__() mapper = self._only_full_mapper_zero("get") is_dict = isinstance(primary_key_identity, dict) if not is_dict: primary_key_identity = util.to_list(primary_key_identity) if len(primary_key_identity) != len(mapper.primary_key): raise sa_exc.InvalidRequestError( "Incorrect number of values in identifier to formulate " "primary key for query.get(); primary key columns are %s" % ",".join("'%s'" % c for c in mapper.primary_key) ) if is_dict: try: primary_key_identity = list( primary_key_identity[prop.key] for prop in mapper._identity_key_props ) except KeyError: raise sa_exc.InvalidRequestError( "Incorrect names of values in identifier to formulate " "primary key for query.get(); primary key attribute names" " are %s" % ",".join( "'%s'" % prop.key for prop in mapper._identity_key_props ) ) if ( not self._populate_existing and not mapper.always_refresh and self._for_update_arg is None ): instance = self._identity_lookup( mapper, primary_key_identity, identity_token=identity_token ) if instance is not None: self._get_existing_condition() # reject calls for id in identity map but class # mismatch. if not issubclass(instance.__class__, mapper.class_): return None return instance return db_load_fn(self, primary_key_identity) @_generative() def correlate(self, *args): """Return a :class:`.Query` construct which will correlate the given FROM clauses to that of an enclosing :class:`.Query` or :func:`~.expression.select`. The method here accepts mapped classes, :func:`.aliased` constructs, and :func:`.mapper` constructs as arguments, which are resolved into expression constructs, in addition to appropriate expression constructs. The correlation arguments are ultimately passed to :meth:`.Select.correlate` after coercion to expression constructs. The correlation arguments take effect in such cases as when :meth:`.Query.from_self` is used, or when a subquery as returned by :meth:`.Query.subquery` is embedded in another :func:`~.expression.select` construct. """ for s in args: if s is None: self._correlate = self._correlate.union([None]) else: self._correlate = self._correlate.union( sql_util.surface_selectables(_interpret_as_from(s)) ) @_generative() def autoflush(self, setting): """Return a Query with a specific 'autoflush' setting. Note that a Session with autoflush=False will not autoflush, even if this flag is set to True at the Query level. Therefore this flag is usually used only to disable autoflush for a specific Query. """ self._autoflush = setting @_generative() def populate_existing(self): """Return a :class:`.Query` that will expire and refresh all instances as they are loaded, or reused from the current :class:`.Session`. :meth:`.populate_existing` does not improve behavior when the ORM is used normally - the :class:`.Session` object's usual behavior of maintaining a transaction and expiring all attributes after rollback or commit handles object state automatically. This method is not intended for general use. """ self._populate_existing = True @_generative() def _with_invoke_all_eagers(self, value): """Set the 'invoke all eagers' flag which causes joined- and subquery loaders to traverse into already-loaded related objects and collections. Default is that of :attr:`.Query._invoke_all_eagers`. """ self._invoke_all_eagers = value def with_parent(self, instance, property=None, from_entity=None): # noqa """Add filtering criterion that relates the given instance to a child object or collection, using its attribute state as well as an established :func:`.relationship()` configuration. The method uses the :func:`.with_parent` function to generate the clause, the result of which is passed to :meth:`.Query.filter`. Parameters are the same as :func:`.with_parent`, with the exception that the given property can be None, in which case a search is performed against this :class:`.Query` object's target mapper. :param instance: An instance which has some :func:`.relationship`. :param property: String property name, or class-bound attribute, which indicates what relationship from the instance should be used to reconcile the parent/child relationship. :param from_entity: Entity in which to consider as the left side. This defaults to the "zero" entity of the :class:`.Query` itself. """ if from_entity: entity_zero = inspect(from_entity) else: entity_zero = self._entity_zero() if property is None: mapper = object_mapper(instance) for prop in mapper.iterate_properties: if ( isinstance(prop, properties.RelationshipProperty) and prop.mapper is entity_zero.mapper ): property = prop # noqa break else: raise sa_exc.InvalidRequestError( "Could not locate a property which relates instances " "of class '%s' to instances of class '%s'" % ( entity_zero.mapper.class_.__name__, instance.__class__.__name__, ) ) return self.filter(with_parent(instance, property, entity_zero.entity)) @_generative() def add_entity(self, entity, alias=None): """add a mapped entity to the list of result columns to be returned.""" if alias is not None: entity = aliased(entity, alias) self._entities = list(self._entities) m = _MapperEntity(self, entity) self._set_entity_selectables([m]) @_generative() def with_session(self, session): """Return a :class:`.Query` that will use the given :class:`.Session`. While the :class:`.Query` object is normally instantiated using the :meth:`.Session.query` method, it is legal to build the :class:`.Query` directly without necessarily using a :class:`.Session`. Such a :class:`.Query` object, or any :class:`.Query` already associated with a different :class:`.Session`, can produce a new :class:`.Query` object associated with a target session using this method:: from sqlalchemy.orm import Query query = Query([MyClass]).filter(MyClass.id == 5) result = query.with_session(my_session).one() """ self.session = session def from_self(self, *entities): r"""return a Query that selects from this Query's SELECT statement. :meth:`.Query.from_self` essentially turns the SELECT statement into a SELECT of itself. Given a query such as:: q = session.query(User).filter(User.name.like('e%')) Given the :meth:`.Query.from_self` version:: q = session.query(User).filter(User.name.like('e%')).from_self() This query renders as: .. sourcecode:: sql SELECT anon_1.user_id AS anon_1_user_id, anon_1.user_name AS anon_1_user_name FROM (SELECT "user".id AS user_id, "user".name AS user_name FROM "user" WHERE "user".name LIKE :name_1) AS anon_1 There are lots of cases where :meth:`.Query.from_self` may be useful. A simple one is where above, we may want to apply a row LIMIT to the set of user objects we query against, and then apply additional joins against that row-limited set:: q = session.query(User).filter(User.name.like('e%')).\ limit(5).from_self().\ join(User.addresses).filter(Address.email.like('q%')) The above query joins to the ``Address`` entity but only against the first five results of the ``User`` query: .. sourcecode:: sql SELECT anon_1.user_id AS anon_1_user_id, anon_1.user_name AS anon_1_user_name FROM (SELECT "user".id AS user_id, "user".name AS user_name FROM "user" WHERE "user".name LIKE :name_1 LIMIT :param_1) AS anon_1 JOIN address ON anon_1.user_id = address.user_id WHERE address.email LIKE :email_1 **Automatic Aliasing** Another key behavior of :meth:`.Query.from_self` is that it applies **automatic aliasing** to the entities inside the subquery, when they are referenced on the outside. Above, if we continue to refer to the ``User`` entity without any additional aliasing applied to it, those references wil be in terms of the subquery:: q = session.query(User).filter(User.name.like('e%')).\ limit(5).from_self().\ join(User.addresses).filter(Address.email.like('q%')).\ order_by(User.name) The ORDER BY against ``User.name`` is aliased to be in terms of the inner subquery: .. sourcecode:: sql SELECT anon_1.user_id AS anon_1_user_id, anon_1.user_name AS anon_1_user_name FROM (SELECT "user".id AS user_id, "user".name AS user_name FROM "user" WHERE "user".name LIKE :name_1 LIMIT :param_1) AS anon_1 JOIN address ON anon_1.user_id = address.user_id WHERE address.email LIKE :email_1 ORDER BY anon_1.user_name The automatic aliasing feature only works in a **limited** way, for simple filters and orderings. More ambitious constructions such as referring to the entity in joins should prefer to use explicit subquery objects, typically making use of the :meth:`.Query.subquery` method to produce an explicit subquery object. Always test the structure of queries by viewing the SQL to ensure a particular structure does what's expected! **Changing the Entities** :meth:`.Query.from_self` also includes the ability to modify what columns are being queried. In our example, we want ``User.id`` to be queried by the inner query, so that we can join to the ``Address`` entity on the outside, but we only wanted the outer query to return the ``Address.email`` column:: q = session.query(User).filter(User.name.like('e%')).\ limit(5).from_self(Address.email).\ join(User.addresses).filter(Address.email.like('q%')) yielding: .. sourcecode:: sql SELECT address.email AS address_email FROM (SELECT "user".id AS user_id, "user".name AS user_name FROM "user" WHERE "user".name LIKE :name_1 LIMIT :param_1) AS anon_1 JOIN address ON anon_1.user_id = address.user_id WHERE address.email LIKE :email_1 **Looking out for Inner / Outer Columns** Keep in mind that when referring to columns that originate from inside the subquery, we need to ensure they are present in the columns clause of the subquery itself; this is an ordinary aspect of SQL. For example, if we wanted to load from a joined entity inside the subquery using :func:`.contains_eager`, we need to add those columns. Below illustrates a join of ``Address`` to ``User``, then a subquery, and then we'd like :func:`.contains_eager` to access the ``User`` columns:: q = session.query(Address).join(Address.user).\ filter(User.name.like('e%')) q = q.add_entity(User).from_self().\ options(contains_eager(Address.user)) We use :meth:`.Query.add_entity` above **before** we call :meth:`.Query.from_self` so that the ``User`` columns are present in the inner subquery, so that they are available to the :func:`.contains_eager` modifier we are using on the outside, producing: .. sourcecode:: sql SELECT anon_1.address_id AS anon_1_address_id, anon_1.address_email AS anon_1_address_email, anon_1.address_user_id AS anon_1_address_user_id, anon_1.user_id AS anon_1_user_id, anon_1.user_name AS anon_1_user_name FROM ( SELECT address.id AS address_id, address.email AS address_email, address.user_id AS address_user_id, "user".id AS user_id, "user".name AS user_name FROM address JOIN "user" ON "user".id = address.user_id WHERE "user".name LIKE :name_1) AS anon_1 If we didn't call ``add_entity(User)``, but still asked :func:`.contains_eager` to load the ``User`` entity, it would be forced to add the table on the outside without the correct join criteria - note the ``anon1, "user"`` phrase at the end: .. sourcecode:: sql -- incorrect query SELECT anon_1.address_id AS anon_1_address_id, anon_1.address_email AS anon_1_address_email, anon_1.address_user_id AS anon_1_address_user_id, "user".id AS user_id, "user".name AS user_name FROM ( SELECT address.id AS address_id, address.email AS address_email, address.user_id AS address_user_id FROM address JOIN "user" ON "user".id = address.user_id WHERE "user".name LIKE :name_1) AS anon_1, "user" :param \*entities: optional list of entities which will replace those being selected. """ fromclause = ( self.with_labels() .enable_eagerloads(False) .statement.correlate(None) ) q = self._from_selectable(fromclause) q._enable_single_crit = False q._select_from_entity = self._entity_zero() if entities: q._set_entities(entities) return q @_generative() def _set_enable_single_crit(self, val): self._enable_single_crit = val @_generative() def _from_selectable(self, fromclause): for attr in ( "_statement", "_criterion", "_order_by", "_group_by", "_limit", "_offset", "_joinpath", "_joinpoint", "_distinct", "_having", "_prefixes", "_suffixes", ): self.__dict__.pop(attr, None) self._set_select_from([fromclause], True) # this enables clause adaptation for non-ORM # expressions. self._orm_only_from_obj_alias = False old_entities = self._entities self._entities = [] for e in old_entities: e.adapt_to_selectable(self, self._from_obj[0]) def values(self, *columns): """Return an iterator yielding result tuples corresponding to the given list of columns""" if not columns: return iter(()) q = self._clone() q._set_entities(columns, entity_wrapper=_ColumnEntity) if not q._yield_per: q._yield_per = 10 return iter(q) _values = values def value(self, column): """Return a scalar result corresponding to the given column expression.""" try: return next(self.values(column))[0] except StopIteration: return None @_generative() def with_entities(self, *entities): r"""Return a new :class:`.Query` replacing the SELECT list with the given entities. e.g.:: # Users, filtered on some arbitrary criterion # and then ordered by related email address q = session.query(User).\ join(User.address).\ filter(User.name.like('%ed%')).\ order_by(Address.email) # given *only* User.id==5, Address.email, and 'q', what # would the *next* User in the result be ? subq = q.with_entities(Address.email).\ order_by(None).\ filter(User.id==5).\ subquery() q = q.join((subq, subq.c.email < Address.email)).\ limit(1) """ self._set_entities(entities) @_generative() def add_columns(self, *column): """Add one or more column expressions to the list of result columns to be returned.""" self._entities = list(self._entities) l = len(self._entities) for c in column: _ColumnEntity(self, c) # _ColumnEntity may add many entities if the # given arg is a FROM clause self._set_entity_selectables(self._entities[l:]) @util.pending_deprecation( "0.7", ":meth:`.add_column` is superseded " "by :meth:`.add_columns`", False, ) def add_column(self, column): """Add a column expression to the list of result columns to be returned. Pending deprecation: :meth:`.add_column` will be superseded by :meth:`.add_columns`. """ return self.add_columns(column) def options(self, *args): """Return a new Query object, applying the given list of mapper options. Most supplied options regard changing how column- and relationship-mapped attributes are loaded. See the sections :ref:`deferred` and :doc:`/orm/loading_relationships` for reference documentation. """ return self._options(False, *args) def _conditional_options(self, *args): return self._options(True, *args) @_generative() def _options(self, conditional, *args): # most MapperOptions write to the '_attributes' dictionary, # so copy that as well self._attributes = self._attributes.copy() if "_unbound_load_dedupes" not in self._attributes: self._attributes["_unbound_load_dedupes"] = set() opts = tuple(util.flatten_iterator(args)) self._with_options = self._with_options + opts if conditional: for opt in opts: opt.process_query_conditionally(self) else: for opt in opts: opt.process_query(self) def with_transformation(self, fn): """Return a new :class:`.Query` object transformed by the given function. E.g.:: def filter_something(criterion): def transform(q): return q.filter(criterion) return transform q = q.with_transformation(filter_something(x==5)) This allows ad-hoc recipes to be created for :class:`.Query` objects. See the example at :ref:`hybrid_transformers`. """ return fn(self) @_generative() def with_hint(self, selectable, text, dialect_name="*"): """Add an indexing or other executional context hint for the given entity or selectable to this :class:`.Query`. Functionality is passed straight through to :meth:`~sqlalchemy.sql.expression.Select.with_hint`, with the addition that ``selectable`` can be a :class:`.Table`, :class:`.Alias`, or ORM entity / mapped class /etc. .. seealso:: :meth:`.Query.with_statement_hint` :meth:.`.Query.prefix_with` - generic SELECT prefixing which also can suit some database-specific HINT syntaxes such as MySQL optimizer hints """ if selectable is not None: selectable = inspect(selectable).selectable self._with_hints += ((selectable, text, dialect_name),) def with_statement_hint(self, text, dialect_name="*"): """add a statement hint to this :class:`.Select`. This method is similar to :meth:`.Select.with_hint` except that it does not require an individual table, and instead applies to the statement as a whole. This feature calls down into :meth:`.Select.with_statement_hint`. .. versionadded:: 1.0.0 .. seealso:: :meth:`.Query.with_hint` """ return self.with_hint(None, text, dialect_name) def get_execution_options(self): """ Get the non-SQL options which will take effect during execution. .. versionadded:: 1.3 .. seealso:: :meth:`.Query.execution_options` """ return self._execution_options @_generative() def execution_options(self, **kwargs): """ Set non-SQL options which take effect during execution. The options are the same as those accepted by :meth:`.Connection.execution_options`. Note that the ``stream_results`` execution option is enabled automatically if the :meth:`~sqlalchemy.orm.query.Query.yield_per()` method is used. .. seealso:: :meth:`.Query.get_execution_options` """ self._execution_options = self._execution_options.union(kwargs) @_generative() @util.deprecated( "0.9", "The :meth:`.Query.with_lockmode` method is deprecated and will " "be removed in a future release. Please refer to " ":meth:`.Query.with_for_update`. ", ) def with_lockmode(self, mode): """Return a new :class:`.Query` object with the specified "locking mode", which essentially refers to the ``FOR UPDATE`` clause. :param mode: a string representing the desired locking mode. Valid values are: * ``None`` - translates to no lockmode * ``'update'`` - translates to ``FOR UPDATE`` (standard SQL, supported by most dialects) * ``'update_nowait'`` - translates to ``FOR UPDATE NOWAIT`` (supported by Oracle, PostgreSQL 8.1 upwards) * ``'read'`` - translates to ``LOCK IN SHARE MODE`` (for MySQL), and ``FOR SHARE`` (for PostgreSQL) .. seealso:: :meth:`.Query.with_for_update` - improved API for specifying the ``FOR UPDATE`` clause. """ self._for_update_arg = LockmodeArg.parse_legacy_query(mode) @_generative() def with_for_update( self, read=False, nowait=False, of=None, skip_locked=False, key_share=False, ): """return a new :class:`.Query` with the specified options for the ``FOR UPDATE`` clause. The behavior of this method is identical to that of :meth:`.SelectBase.with_for_update`. When called with no arguments, the resulting ``SELECT`` statement will have a ``FOR UPDATE`` clause appended. When additional arguments are specified, backend-specific options such as ``FOR UPDATE NOWAIT`` or ``LOCK IN SHARE MODE`` can take effect. E.g.:: q = sess.query(User).with_for_update(nowait=True, of=User) The above query on a PostgreSQL backend will render like:: SELECT users.id AS users_id FROM users FOR UPDATE OF users NOWAIT .. versionadded:: 0.9.0 :meth:`.Query.with_for_update` supersedes the :meth:`.Query.with_lockmode` method. .. seealso:: :meth:`.GenerativeSelect.with_for_update` - Core level method with full argument and behavioral description. """ self._for_update_arg = LockmodeArg( read=read, nowait=nowait, of=of, skip_locked=skip_locked, key_share=key_share, ) @_generative() def params(self, *args, **kwargs): r"""add values for bind parameters which may have been specified in filter(). parameters may be specified using \**kwargs, or optionally a single dictionary as the first positional argument. The reason for both is that \**kwargs is convenient, however some parameter dictionaries contain unicode keys in which case \**kwargs cannot be used. """ if len(args) == 1: kwargs.update(args[0]) elif len(args) > 0: raise sa_exc.ArgumentError( "params() takes zero or one positional argument, " "which is a dictionary." ) self._params = self._params.copy() self._params.update(kwargs) @_generative(_no_statement_condition, _no_limit_offset) def filter(self, *criterion): r"""apply the given filtering criterion to a copy of this :class:`.Query`, using SQL expressions. e.g.:: session.query(MyClass).filter(MyClass.name == 'some name') Multiple criteria may be specified as comma separated; the effect is that they will be joined together using the :func:`.and_` function:: session.query(MyClass).\ filter(MyClass.name == 'some name', MyClass.id > 5) The criterion is any SQL expression object applicable to the WHERE clause of a select. String expressions are coerced into SQL expression constructs via the :func:`.text` construct. .. seealso:: :meth:`.Query.filter_by` - filter on keyword expressions. """ for criterion in list(criterion): criterion = expression._expression_literal_as_text(criterion) criterion = self._adapt_clause(criterion, True, True) if self._criterion is not None: self._criterion = self._criterion & criterion else: self._criterion = criterion def filter_by(self, **kwargs): r"""apply the given filtering criterion to a copy of this :class:`.Query`, using keyword expressions. e.g.:: session.query(MyClass).filter_by(name = 'some name') Multiple criteria may be specified as comma separated; the effect is that they will be joined together using the :func:`.and_` function:: session.query(MyClass).\ filter_by(name = 'some name', id = 5) The keyword expressions are extracted from the primary entity of the query, or the last entity that was the target of a call to :meth:`.Query.join`. .. seealso:: :meth:`.Query.filter` - filter on SQL expressions. """ clauses = [ _entity_descriptor(self._joinpoint_zero(), key) == value for key, value in kwargs.items() ] return self.filter(*clauses) @_generative(_no_statement_condition, _no_limit_offset) def order_by(self, *criterion): """apply one or more ORDER BY criterion to the query and return the newly resulting ``Query`` All existing ORDER BY settings can be suppressed by passing ``None`` - this will suppress any ordering configured on the :func:`.mapper` object using the deprecated :paramref:`.mapper.order_by` parameter. """ if len(criterion) == 1: if criterion[0] is False: if "_order_by" in self.__dict__: self._order_by = False return if criterion[0] is None: self._order_by = None return criterion = self._adapt_col_list(criterion) if self._order_by is False or self._order_by is None: self._order_by = criterion else: self._order_by = self._order_by + criterion @_generative(_no_statement_condition, _no_limit_offset) def group_by(self, *criterion): """apply one or more GROUP BY criterion to the query and return the newly resulting :class:`.Query` All existing GROUP BY settings can be suppressed by passing ``None`` - this will suppress any GROUP BY configured on mappers as well. .. versionadded:: 1.1 GROUP BY can be cancelled by passing None, in the same way as ORDER BY. """ if len(criterion) == 1: if criterion[0] is None: self._group_by = False return criterion = list(chain(*[_orm_columns(c) for c in criterion])) criterion = self._adapt_col_list(criterion) if self._group_by is False: self._group_by = criterion else: self._group_by = self._group_by + criterion @_generative(_no_statement_condition, _no_limit_offset) def having(self, criterion): r"""apply a HAVING criterion to the query and return the newly resulting :class:`.Query`. :meth:`~.Query.having` is used in conjunction with :meth:`~.Query.group_by`. HAVING criterion makes it possible to use filters on aggregate functions like COUNT, SUM, AVG, MAX, and MIN, eg.:: q = session.query(User.id).\ join(User.addresses).\ group_by(User.id).\ having(func.count(Address.id) > 2) """ criterion = expression._expression_literal_as_text(criterion) if criterion is not None and not isinstance( criterion, sql.ClauseElement ): raise sa_exc.ArgumentError( "having() argument must be of type " "sqlalchemy.sql.ClauseElement or string" ) criterion = self._adapt_clause(criterion, True, True) if self._having is not None: self._having = self._having & criterion else: self._having = criterion def _set_op(self, expr_fn, *q): return self._from_selectable( expr_fn(*([self] + list(q))) )._set_enable_single_crit(False) def union(self, *q): """Produce a UNION of this Query against one or more queries. e.g.:: q1 = sess.query(SomeClass).filter(SomeClass.foo=='bar') q2 = sess.query(SomeClass).filter(SomeClass.bar=='foo') q3 = q1.union(q2) The method accepts multiple Query objects so as to control the level of nesting. A series of ``union()`` calls such as:: x.union(y).union(z).all() will nest on each ``union()``, and produces:: SELECT * FROM (SELECT * FROM (SELECT * FROM X UNION SELECT * FROM y) UNION SELECT * FROM Z) Whereas:: x.union(y, z).all() produces:: SELECT * FROM (SELECT * FROM X UNION SELECT * FROM y UNION SELECT * FROM Z) Note that many database backends do not allow ORDER BY to be rendered on a query called within UNION, EXCEPT, etc. To disable all ORDER BY clauses including those configured on mappers, issue ``query.order_by(None)`` - the resulting :class:`.Query` object will not render ORDER BY within its SELECT statement. """ return self._set_op(expression.union, *q) def union_all(self, *q): """Produce a UNION ALL of this Query against one or more queries. Works the same way as :meth:`~sqlalchemy.orm.query.Query.union`. See that method for usage examples. """ return self._set_op(expression.union_all, *q) def intersect(self, *q): """Produce an INTERSECT of this Query against one or more queries. Works the same way as :meth:`~sqlalchemy.orm.query.Query.union`. See that method for usage examples. """ return self._set_op(expression.intersect, *q) def intersect_all(self, *q): """Produce an INTERSECT ALL of this Query against one or more queries. Works the same way as :meth:`~sqlalchemy.orm.query.Query.union`. See that method for usage examples. """ return self._set_op(expression.intersect_all, *q) def except_(self, *q): """Produce an EXCEPT of this Query against one or more queries. Works the same way as :meth:`~sqlalchemy.orm.query.Query.union`. See that method for usage examples. """ return self._set_op(expression.except_, *q) def except_all(self, *q): """Produce an EXCEPT ALL of this Query against one or more queries. Works the same way as :meth:`~sqlalchemy.orm.query.Query.union`. See that method for usage examples. """ return self._set_op(expression.except_all, *q) def join(self, *props, **kwargs): r"""Create a SQL JOIN against this :class:`.Query` object's criterion and apply generatively, returning the newly resulting :class:`.Query`. **Simple Relationship Joins** Consider a mapping between two classes ``User`` and ``Address``, with a relationship ``User.addresses`` representing a collection of ``Address`` objects associated with each ``User``. The most common usage of :meth:`~.Query.join` is to create a JOIN along this relationship, using the ``User.addresses`` attribute as an indicator for how this should occur:: q = session.query(User).join(User.addresses) Where above, the call to :meth:`~.Query.join` along ``User.addresses`` will result in SQL equivalent to:: SELECT user.* FROM user JOIN address ON user.id = address.user_id In the above example we refer to ``User.addresses`` as passed to :meth:`~.Query.join` as the *on clause*, that is, it indicates how the "ON" portion of the JOIN should be constructed. For a single-entity query such as the one above (i.e. we start by selecting only from ``User`` and nothing else), the relationship can also be specified by its string name:: q = session.query(User).join("addresses") :meth:`~.Query.join` can also accommodate multiple "on clause" arguments to produce a chain of joins, such as below where a join across four related entities is constructed:: q = session.query(User).join("orders", "items", "keywords") The above would be shorthand for three separate calls to :meth:`~.Query.join`, each using an explicit attribute to indicate the source entity:: q = session.query(User).\ join(User.orders).\ join(Order.items).\ join(Item.keywords) **Joins to a Target Entity or Selectable** A second form of :meth:`~.Query.join` allows any mapped entity or core selectable construct as a target. In this usage, :meth:`~.Query.join` will attempt to create a JOIN along the natural foreign key relationship between two entities:: q = session.query(User).join(Address) The above calling form of :meth:`~.Query.join` will raise an error if either there are no foreign keys between the two entities, or if there are multiple foreign key linkages between them. In the above calling form, :meth:`~.Query.join` is called upon to create the "on clause" automatically for us. The target can be any mapped entity or selectable, such as a :class:`.Table`:: q = session.query(User).join(addresses_table) **Joins to a Target with an ON Clause** The third calling form allows both the target entity as well as the ON clause to be passed explicitly. Suppose for example we wanted to join to ``Address`` twice, using an alias the second time. We use :func:`~sqlalchemy.orm.aliased` to create a distinct alias of ``Address``, and join to it using the ``target, onclause`` form, so that the alias can be specified explicitly as the target along with the relationship to instruct how the ON clause should proceed:: a_alias = aliased(Address) q = session.query(User).\ join(User.addresses).\ join(a_alias, User.addresses).\ filter(Address.email_address=='ed@foo.com').\ filter(a_alias.email_address=='ed@bar.com') Where above, the generated SQL would be similar to:: SELECT user.* FROM user JOIN address ON user.id = address.user_id JOIN address AS address_1 ON user.id=address_1.user_id WHERE address.email_address = :email_address_1 AND address_1.email_address = :email_address_2 The two-argument calling form of :meth:`~.Query.join` also allows us to construct arbitrary joins with SQL-oriented "on clause" expressions, not relying upon configured relationships at all. Any SQL expression can be passed as the ON clause when using the two-argument form, which should refer to the target entity in some way as well as an applicable source entity:: q = session.query(User).join(Address, User.id==Address.user_id) **Advanced Join Targeting and Adaption** There is a lot of flexibility in what the "target" can be when using :meth:`~.Query.join`. As noted previously, it also accepts :class:`.Table` constructs and other selectables such as :func:`.alias` and :func:`.select` constructs, with either the one or two-argument forms:: addresses_q = select([Address.user_id]).\ where(Address.email_address.endswith("@bar.com")).\ alias() q = session.query(User).\ join(addresses_q, addresses_q.c.user_id==User.id) :meth:`~.Query.join` also features the ability to *adapt* a :meth:`~sqlalchemy.orm.relationship` -driven ON clause to the target selectable. Below we construct a JOIN from ``User`` to a subquery against ``Address``, allowing the relationship denoted by ``User.addresses`` to *adapt* itself to the altered target:: address_subq = session.query(Address).\ filter(Address.email_address == 'ed@foo.com').\ subquery() q = session.query(User).join(address_subq, User.addresses) Producing SQL similar to:: SELECT user.* FROM user JOIN ( SELECT address.id AS id, address.user_id AS user_id, address.email_address AS email_address FROM address WHERE address.email_address = :email_address_1 ) AS anon_1 ON user.id = anon_1.user_id The above form allows one to fall back onto an explicit ON clause at any time:: q = session.query(User).\ join(address_subq, User.id==address_subq.c.user_id) **Controlling what to Join From** While :meth:`~.Query.join` exclusively deals with the "right" side of the JOIN, we can also control the "left" side, in those cases where it's needed, using :meth:`~.Query.select_from`. Below we construct a query against ``Address`` but can still make usage of ``User.addresses`` as our ON clause by instructing the :class:`.Query` to select first from the ``User`` entity:: q = session.query(Address).select_from(User).\ join(User.addresses).\ filter(User.name == 'ed') Which will produce SQL similar to:: SELECT address.* FROM user JOIN address ON user.id=address.user_id WHERE user.name = :name_1 **Constructing Aliases Anonymously** :meth:`~.Query.join` can construct anonymous aliases using the ``aliased=True`` flag. This feature is useful when a query is being joined algorithmically, such as when querying self-referentially to an arbitrary depth:: q = session.query(Node).\ join("children", "children", aliased=True) When ``aliased=True`` is used, the actual "alias" construct is not explicitly available. To work with it, methods such as :meth:`.Query.filter` will adapt the incoming entity to the last join point:: q = session.query(Node).\ join("children", "children", aliased=True).\ filter(Node.name == 'grandchild 1') When using automatic aliasing, the ``from_joinpoint=True`` argument can allow a multi-node join to be broken into multiple calls to :meth:`~.Query.join`, so that each path along the way can be further filtered:: q = session.query(Node).\ join("children", aliased=True).\ filter(Node.name='child 1').\ join("children", aliased=True, from_joinpoint=True).\ filter(Node.name == 'grandchild 1') The filtering aliases above can then be reset back to the original ``Node`` entity using :meth:`~.Query.reset_joinpoint`:: q = session.query(Node).\ join("children", "children", aliased=True).\ filter(Node.name == 'grandchild 1').\ reset_joinpoint().\ filter(Node.name == 'parent 1) For an example of ``aliased=True``, see the distribution example :ref:`examples_xmlpersistence` which illustrates an XPath-like query system using algorithmic joins. :param \*props: A collection of one or more join conditions, each consisting of a relationship-bound attribute or string relationship name representing an "on clause", or a single target entity, or a tuple in the form of ``(target, onclause)``. A special two-argument calling form of the form ``target, onclause`` is also accepted. :param aliased=False: If True, indicate that the JOIN target should be anonymously aliased. Subsequent calls to :meth:`~.Query.filter` and similar will adapt the incoming criterion to the target alias, until :meth:`~.Query.reset_joinpoint` is called. :param isouter=False: If True, the join used will be a left outer join, just as if the :meth:`.Query.outerjoin` method were called. This flag is here to maintain consistency with the same flag as accepted by :meth:`.FromClause.join` and other Core constructs. .. versionadded:: 1.0.0 :param full=False: render FULL OUTER JOIN; implies ``isouter``. .. versionadded:: 1.1 :param from_joinpoint=False: When using ``aliased=True``, a setting of True here will cause the join to be from the most recent joined target, rather than starting back from the original FROM clauses of the query. .. seealso:: :ref:`ormtutorial_joins` in the ORM tutorial. :ref:`inheritance_toplevel` for details on how :meth:`~.Query.join` is used for inheritance relationships. :func:`.orm.join` - a standalone ORM-level join function, used internally by :meth:`.Query.join`, which in previous SQLAlchemy versions was the primary ORM-level joining interface. """ aliased, from_joinpoint, isouter, full = ( kwargs.pop("aliased", False), kwargs.pop("from_joinpoint", False), kwargs.pop("isouter", False), kwargs.pop("full", False), ) if kwargs: raise TypeError( "unknown arguments: %s" % ", ".join(sorted(kwargs)) ) return self._join( props, outerjoin=isouter, full=full, create_aliases=aliased, from_joinpoint=from_joinpoint, ) def outerjoin(self, *props, **kwargs): """Create a left outer join against this ``Query`` object's criterion and apply generatively, returning the newly resulting ``Query``. Usage is the same as the ``join()`` method. """ aliased, from_joinpoint, full = ( kwargs.pop("aliased", False), kwargs.pop("from_joinpoint", False), kwargs.pop("full", False), ) if kwargs: raise TypeError( "unknown arguments: %s" % ", ".join(sorted(kwargs)) ) return self._join( props, outerjoin=True, full=full, create_aliases=aliased, from_joinpoint=from_joinpoint, ) def _update_joinpoint(self, jp): self._joinpoint = jp # copy backwards to the root of the _joinpath # dict, so that no existing dict in the path is mutated while "prev" in jp: f, prev = jp["prev"] prev = prev.copy() prev[f] = jp jp["prev"] = (f, prev) jp = prev self._joinpath = jp @_generative(_no_statement_condition, _no_limit_offset) def _join(self, keys, outerjoin, full, create_aliases, from_joinpoint): """consumes arguments from join() or outerjoin(), places them into a consistent format with which to form the actual JOIN constructs. """ if not from_joinpoint: self._reset_joinpoint() if ( len(keys) == 2 and isinstance( keys[0], (expression.FromClause, type, AliasedClass) ) and isinstance( keys[1], (str, expression.ClauseElement, interfaces.PropComparator), ) ): # detect 2-arg form of join and # convert to a tuple. keys = (keys,) # Query.join() accepts a list of join paths all at once. # step one is to iterate through these paths and determine the # intent of each path individually. as we encounter a path token, # we add a new ORMJoin construct to the self._from_obj tuple, # either by adding a new element to it, or by replacing an existing # element with a new ORMJoin. keylist = util.to_list(keys) for idx, arg1 in enumerate(keylist): if isinstance(arg1, tuple): # "tuple" form of join, multiple # tuples are accepted as well. The simpler # "2-arg" form is preferred. arg1, arg2 = arg1 else: arg2 = None # determine onclause/right_entity. there # is a little bit of legacy behavior still at work here # which means they might be in either order. if isinstance( arg1, (interfaces.PropComparator, util.string_types) ): right, onclause = arg2, arg1 else: right, onclause = arg1, arg2 if onclause is None: r_info = inspect(right) if not r_info.is_selectable and not hasattr(r_info, "mapper"): raise sa_exc.ArgumentError( "Expected mapped entity or " "selectable/table as join target" ) if isinstance(onclause, interfaces.PropComparator): of_type = getattr(onclause, "_of_type", None) else: of_type = None if isinstance(onclause, util.string_types): # string given, e.g. query(Foo).join("bar"). # we look to the left entity or what we last joined # towards onclause = _entity_descriptor(self._joinpoint_zero(), onclause) # check for q.join(Class.propname, from_joinpoint=True) # and Class corresponds at the mapper level to the current # joinpoint. this match intentionally looks for a non-aliased # class-bound descriptor as the onclause and if it matches the # current joinpoint at the mapper level, it's used. This # is a very old use case that is intended to make it easier # to work with the aliased=True flag, which is also something # that probably shouldn't exist on join() due to its high # complexity/usefulness ratio elif from_joinpoint and isinstance( onclause, interfaces.PropComparator ): jp0 = self._joinpoint_zero() info = inspect(jp0) if getattr(info, "mapper", None) is onclause._parententity: onclause = _entity_descriptor(jp0, onclause.key) if isinstance(onclause, interfaces.PropComparator): # descriptor/property given (or determined); this tells # us explicitly what the expected "left" side of the join is. if right is None: if of_type: right = of_type else: right = onclause.property.entity left = onclause._parententity alias = self._polymorphic_adapters.get(left, None) # could be None or could be ColumnAdapter also if isinstance(alias, ORMAdapter) and alias.mapper.isa(left): left = alias.aliased_class onclause = getattr(left, onclause.key) prop = onclause.property if not isinstance(onclause, attributes.QueryableAttribute): onclause = prop if not create_aliases: # check for this path already present. # don't render in that case. edge = (left, right, prop.key) if edge in self._joinpoint: # The child's prev reference might be stale -- # it could point to a parent older than the # current joinpoint. If this is the case, # then we need to update it and then fix the # tree's spine with _update_joinpoint. Copy # and then mutate the child, which might be # shared by a different query object. jp = self._joinpoint[edge].copy() jp["prev"] = (edge, self._joinpoint) self._update_joinpoint(jp) # warn only on the last element of the list if idx == len(keylist) - 1: util.warn( "Pathed join target %s has already " "been joined to; skipping" % prop ) continue else: # no descriptor/property given; we will need to figure out # what the effective "left" side is prop = left = None # figure out the final "left" and "right" sides and create an # ORMJoin to add to our _from_obj tuple self._join_left_to_right( left, right, onclause, prop, create_aliases, outerjoin, full ) def _join_left_to_right( self, left, right, onclause, prop, create_aliases, outerjoin, full ): """given raw "left", "right", "onclause" parameters consumed from a particular key within _join(), add a real ORMJoin object to our _from_obj list (or augment an existing one) """ self._polymorphic_adapters = self._polymorphic_adapters.copy() if left is None: # left not given (e.g. no relationship object/name specified) # figure out the best "left" side based on our existing froms / # entities assert prop is None ( left, replace_from_obj_index, use_entity_index, ) = self._join_determine_implicit_left_side(left, right, onclause) else: # left is given via a relationship/name. Determine where in our # "froms" list it should be spliced/appended as well as what # existing entity it corresponds to. assert prop is not None ( replace_from_obj_index, use_entity_index, ) = self._join_place_explicit_left_side(left) # this should never happen because we would not have found a place # to join on assert left is not right or create_aliases # the right side as given often needs to be adapted. additionally # a lot of things can be wrong with it. handle all that and # get back the new effective "right" side r_info, right, onclause = self._join_check_and_adapt_right_side( left, right, onclause, prop, create_aliases ) if replace_from_obj_index is not None: # splice into an existing element in the # self._from_obj list left_clause = self._from_obj[replace_from_obj_index] self._from_obj = ( self._from_obj[:replace_from_obj_index] + ( orm_join( left_clause, right, onclause, isouter=outerjoin, full=full, ), ) + self._from_obj[replace_from_obj_index + 1 :] ) else: # add a new element to the self._from_obj list if use_entity_index is not None: # why doesn't this work as .entity_zero_or_selectable? left_clause = self._entities[use_entity_index].selectable else: left_clause = left self._from_obj = self._from_obj + ( orm_join( left_clause, right, onclause, isouter=outerjoin, full=full ), ) def _join_determine_implicit_left_side(self, left, right, onclause): """When join conditions don't express the left side explicitly, determine if an existing FROM or entity in this query can serve as the left hand side. """ # when we are here, it means join() was called without an ORM- # specific way of telling us what the "left" side is, e.g.: # # join(RightEntity) # # or # # join(RightEntity, RightEntity.foo == LeftEntity.bar) # r_info = inspect(right) replace_from_obj_index = use_entity_index = None if self._from_obj: # we have a list of FROMs already. So by definition this # join has to connect to one of those FROMs. indexes = sql_util.find_left_clause_to_join_from( self._from_obj, r_info.selectable, onclause ) if len(indexes) == 1: replace_from_obj_index = indexes[0] left = self._from_obj[replace_from_obj_index] elif len(indexes) > 1: raise sa_exc.InvalidRequestError( "Can't determine which FROM clause to join " "from, there are multiple FROMS which can " "join to this entity. Try adding an explicit ON clause " "to help resolve the ambiguity." ) else: raise sa_exc.InvalidRequestError( "Don't know how to join to %s; please use " "an ON clause to more clearly establish the left " "side of this join" % (right,) ) elif self._entities: # we have no explicit FROMs, so the implicit left has to # come from our list of entities. potential = {} for entity_index, ent in enumerate(self._entities): entity = ent.entity_zero_or_selectable if entity is None: continue ent_info = inspect(entity) if ent_info is r_info: # left and right are the same, skip continue # by using a dictionary with the selectables as keys this # de-duplicates those selectables as occurs when the query is # against a series of columns from the same selectable if isinstance(ent, _MapperEntity): potential[ent.selectable] = (entity_index, entity) else: potential[ent_info.selectable] = (None, entity) all_clauses = list(potential.keys()) indexes = sql_util.find_left_clause_to_join_from( all_clauses, r_info.selectable, onclause ) if len(indexes) == 1: use_entity_index, left = potential[all_clauses[indexes[0]]] elif len(indexes) > 1: raise sa_exc.InvalidRequestError( "Can't determine which FROM clause to join " "from, there are multiple FROMS which can " "join to this entity. Try adding an explicit ON clause " "to help resolve the ambiguity." ) else: raise sa_exc.InvalidRequestError( "Don't know how to join to %s; please use " "an ON clause to more clearly establish the left " "side of this join" % (right,) ) else: raise sa_exc.InvalidRequestError( "No entities to join from; please use " "select_from() to establish the left " "entity/selectable of this join" ) return left, replace_from_obj_index, use_entity_index def _join_place_explicit_left_side(self, left): """When join conditions express a left side explicitly, determine where in our existing list of FROM clauses we should join towards, or if we need to make a new join, and if so is it from one of our existing entities. """ # when we are here, it means join() was called with an indicator # as to an exact left side, which means a path to a # RelationshipProperty was given, e.g.: # # join(RightEntity, LeftEntity.right) # # or # # join(LeftEntity.right) # # as well as string forms: # # join(RightEntity, "right") # # etc. # replace_from_obj_index = use_entity_index = None l_info = inspect(left) if self._from_obj: indexes = sql_util.find_left_clause_that_matches_given( self._from_obj, l_info.selectable ) if len(indexes) > 1: raise sa_exc.InvalidRequestError( "Can't identify which entity in which to assign the " "left side of this join. Please use a more specific " "ON clause." ) # have an index, means the left side is already present in # an existing FROM in the self._from_obj tuple if indexes: replace_from_obj_index = indexes[0] # no index, means we need to add a new element to the # self._from_obj tuple # no from element present, so we will have to add to the # self._from_obj tuple. Determine if this left side matches up # with existing mapper entities, in which case we want to apply the # aliasing / adaptation rules present on that entity if any if ( replace_from_obj_index is None and self._entities and hasattr(l_info, "mapper") ): for idx, ent in enumerate(self._entities): # TODO: should we be checking for multiple mapper entities # matching? if isinstance(ent, _MapperEntity) and ent.corresponds_to(left): use_entity_index = idx break return replace_from_obj_index, use_entity_index def _join_check_and_adapt_right_side( self, left, right, onclause, prop, create_aliases ): """transform the "right" side of the join as well as the onclause according to polymorphic mapping translations, aliasing on the query or on the join, special cases where the right and left side have overlapping tables. """ l_info = inspect(left) r_info = inspect(right) overlap = False if not create_aliases: right_mapper = getattr(r_info, "mapper", None) # if the target is a joined inheritance mapping, # be more liberal about auto-aliasing. if right_mapper and ( right_mapper.with_polymorphic or isinstance(right_mapper.persist_selectable, expression.Join) ): for from_obj in self._from_obj or [l_info.selectable]: if sql_util.selectables_overlap( l_info.selectable, from_obj ) and sql_util.selectables_overlap( from_obj, r_info.selectable ): overlap = True break if ( overlap or not create_aliases ) and l_info.selectable is r_info.selectable: raise sa_exc.InvalidRequestError( "Can't join table/selectable '%s' to itself" % l_info.selectable ) right_mapper, right_selectable, right_is_aliased = ( getattr(r_info, "mapper", None), r_info.selectable, getattr(r_info, "is_aliased_class", False), ) if ( right_mapper and prop and not right_mapper.common_parent(prop.mapper) ): raise sa_exc.InvalidRequestError( "Join target %s does not correspond to " "the right side of join condition %s" % (right, onclause) ) # _join_entities is used as a hint for single-table inheritance # purposes at the moment if hasattr(r_info, "mapper"): self._join_entities += (r_info,) need_adapter = False # test for joining to an unmapped selectable as the target if r_info.is_clause_element: if prop: right_mapper = prop.mapper if right_selectable._is_lateral: # orm_only is disabled to suit the case where we have to # adapt an explicit correlate(Entity) - the select() loses # the ORM-ness in this case right now, ideally it would not right = self._adapt_clause(right, True, False) elif prop: # joining to selectable with a mapper property given # as the ON clause if not right_selectable.is_derived_from( right_mapper.persist_selectable ): raise sa_exc.InvalidRequestError( "Selectable '%s' is not derived from '%s'" % ( right_selectable.description, right_mapper.persist_selectable.description, ) ) # if the destination selectable is a plain select(), # turn it into an alias(). if isinstance(right_selectable, expression.SelectBase): right_selectable = right_selectable.alias() need_adapter = True # make the right hand side target into an ORM entity right = aliased(right_mapper, right_selectable) elif create_aliases: # it *could* work, but it doesn't right now and I'd rather # get rid of aliased=True completely raise sa_exc.InvalidRequestError( "The aliased=True parameter on query.join() only works " "with an ORM entity, not a plain selectable, as the " "target." ) aliased_entity = ( right_mapper and not right_is_aliased and ( right_mapper.with_polymorphic and isinstance( right_mapper._with_polymorphic_selectable, expression.Alias ) or overlap # test for overlap: # orm/inheritance/relationships.py # SelfReferentialM2MTest ) ) if not need_adapter and (create_aliases or aliased_entity): right = aliased(right, flat=True) need_adapter = True if need_adapter: assert right_mapper # if an alias() of the right side was generated, # apply an adapter to all subsequent filter() calls # until reset_joinpoint() is called. adapter = ORMAdapter( right, equivalents=right_mapper._equivalent_columns ) # current adapter takes highest precedence self._filter_aliases = (adapter,) + self._filter_aliases # if an alias() on the right side was generated, # which is intended to wrap a the right side in a subquery, # ensure that columns retrieved from this target in the result # set are also adapted. if not create_aliases: self._mapper_loads_polymorphically_with(right_mapper, adapter) # if the onclause is a ClauseElement, adapt it with any # adapters that are in place right now if isinstance(onclause, expression.ClauseElement): onclause = self._adapt_clause(onclause, True, True) # if joining on a MapperProperty path, # track the path to prevent redundant joins if not create_aliases and prop: self._update_joinpoint( { "_joinpoint_entity": right, "prev": ((left, right, prop.key), self._joinpoint), } ) else: self._joinpoint = {"_joinpoint_entity": right} return right, inspect(right), onclause def _reset_joinpoint(self): self._joinpoint = self._joinpath self._filter_aliases = () @_generative(_no_statement_condition) def reset_joinpoint(self): """Return a new :class:`.Query`, where the "join point" has been reset back to the base FROM entities of the query. This method is usually used in conjunction with the ``aliased=True`` feature of the :meth:`~.Query.join` method. See the example in :meth:`~.Query.join` for how this is used. """ self._reset_joinpoint() @_generative(_no_clauseelement_condition) def select_from(self, *from_obj): r"""Set the FROM clause of this :class:`.Query` explicitly. :meth:`.Query.select_from` is often used in conjunction with :meth:`.Query.join` in order to control which entity is selected from on the "left" side of the join. The entity or selectable object here effectively replaces the "left edge" of any calls to :meth:`~.Query.join`, when no joinpoint is otherwise established - usually, the default "join point" is the leftmost entity in the :class:`~.Query` object's list of entities to be selected. A typical example:: q = session.query(Address).select_from(User).\ join(User.addresses).\ filter(User.name == 'ed') Which produces SQL equivalent to:: SELECT address.* FROM user JOIN address ON user.id=address.user_id WHERE user.name = :name_1 :param \*from_obj: collection of one or more entities to apply to the FROM clause. Entities can be mapped classes, :class:`.AliasedClass` objects, :class:`.Mapper` objects as well as core :class:`.FromClause` elements like subqueries. .. versionchanged:: 0.9 This method no longer applies the given FROM object to be the selectable from which matching entities select from; the :meth:`.select_entity_from` method now accomplishes this. See that method for a description of this behavior. .. seealso:: :meth:`~.Query.join` :meth:`.Query.select_entity_from` """ self._set_select_from(from_obj, False) @_generative(_no_clauseelement_condition) def select_entity_from(self, from_obj): r"""Set the FROM clause of this :class:`.Query` to a core selectable, applying it as a replacement FROM clause for corresponding mapped entities. The :meth:`.Query.select_entity_from` method supplies an alternative approach to the use case of applying an :func:`.aliased` construct explicitly throughout a query. Instead of referring to the :func:`.aliased` construct explicitly, :meth:`.Query.select_entity_from` automatically *adapts* all occurrences of the entity to the target selectable. Given a case for :func:`.aliased` such as selecting ``User`` objects from a SELECT statement:: select_stmt = select([User]).where(User.id == 7) user_alias = aliased(User, select_stmt) q = session.query(user_alias).\ filter(user_alias.name == 'ed') Above, we apply the ``user_alias`` object explicitly throughout the query. When it's not feasible for ``user_alias`` to be referenced explicitly in many places, :meth:`.Query.select_entity_from` may be used at the start of the query to adapt the existing ``User`` entity:: q = session.query(User).\ select_entity_from(select_stmt).\ filter(User.name == 'ed') Above, the generated SQL will show that the ``User`` entity is adapted to our statement, even in the case of the WHERE clause: .. sourcecode:: sql SELECT anon_1.id AS anon_1_id, anon_1.name AS anon_1_name FROM (SELECT "user".id AS id, "user".name AS name FROM "user" WHERE "user".id = :id_1) AS anon_1 WHERE anon_1.name = :name_1 The :meth:`.Query.select_entity_from` method is similar to the :meth:`.Query.select_from` method, in that it sets the FROM clause of the query. The difference is that it additionally applies adaptation to the other parts of the query that refer to the primary entity. If above we had used :meth:`.Query.select_from` instead, the SQL generated would have been: .. sourcecode:: sql -- uses plain select_from(), not select_entity_from() SELECT "user".id AS user_id, "user".name AS user_name FROM "user", (SELECT "user".id AS id, "user".name AS name FROM "user" WHERE "user".id = :id_1) AS anon_1 WHERE "user".name = :name_1 To supply textual SQL to the :meth:`.Query.select_entity_from` method, we can make use of the :func:`.text` construct. However, the :func:`.text` construct needs to be aligned with the columns of our entity, which is achieved by making use of the :meth:`.TextClause.columns` method:: text_stmt = text("select id, name from user").columns( User.id, User.name) q = session.query(User).select_entity_from(text_stmt) :meth:`.Query.select_entity_from` itself accepts an :func:`.aliased` object, so that the special options of :func:`.aliased` such as :paramref:`.aliased.adapt_on_names` may be used within the scope of the :meth:`.Query.select_entity_from` method's adaptation services. Suppose a view ``user_view`` also returns rows from ``user``. If we reflect this view into a :class:`.Table`, this view has no relationship to the :class:`.Table` to which we are mapped, however we can use name matching to select from it:: user_view = Table('user_view', metadata, autoload_with=engine) user_view_alias = aliased( User, user_view, adapt_on_names=True) q = session.query(User).\ select_entity_from(user_view_alias).\ order_by(User.name) .. versionchanged:: 1.1.7 The :meth:`.Query.select_entity_from` method now accepts an :func:`.aliased` object as an alternative to a :class:`.FromClause` object. :param from_obj: a :class:`.FromClause` object that will replace the FROM clause of this :class:`.Query`. It also may be an instance of :func:`.aliased`. .. seealso:: :meth:`.Query.select_from` """ self._set_select_from([from_obj], True) def __getitem__(self, item): if isinstance(item, slice): start, stop, step = util.decode_slice(item) if ( isinstance(stop, int) and isinstance(start, int) and stop - start <= 0 ): return [] # perhaps we should execute a count() here so that we # can still use LIMIT/OFFSET ? elif (isinstance(start, int) and start < 0) or ( isinstance(stop, int) and stop < 0 ): return list(self)[item] res = self.slice(start, stop) if step is not None: return list(res)[None : None : item.step] else: return list(res) else: if item == -1: return list(self)[-1] else: return list(self[item : item + 1])[0] @_generative(_no_statement_condition) def slice(self, start, stop): """Computes the "slice" of the :class:`.Query` represented by the given indices and returns the resulting :class:`.Query`. The start and stop indices behave like the argument to Python's built-in :func:`range` function. This method provides an alternative to using ``LIMIT``/``OFFSET`` to get a slice of the query. For example, :: session.query(User).order_by(User.id).slice(1, 3) renders as .. sourcecode:: sql SELECT users.id AS users_id, users.name AS users_name FROM users ORDER BY users.id LIMIT ? OFFSET ? (2, 1) .. seealso:: :meth:`.Query.limit` :meth:`.Query.offset` """ if start is not None and stop is not None: self._offset = (self._offset or 0) + start self._limit = stop - start elif start is None and stop is not None: self._limit = stop elif start is not None and stop is None: self._offset = (self._offset or 0) + start if self._offset == 0: self._offset = None @_generative(_no_statement_condition) def limit(self, limit): """Apply a ``LIMIT`` to the query and return the newly resulting ``Query``. """ self._limit = limit @_generative(_no_statement_condition) def offset(self, offset): """Apply an ``OFFSET`` to the query and return the newly resulting ``Query``. """ self._offset = offset @_generative(_no_statement_condition) def distinct(self, *expr): r"""Apply a ``DISTINCT`` to the query and return the newly resulting ``Query``. .. note:: The :meth:`.distinct` call includes logic that will automatically add columns from the ORDER BY of the query to the columns clause of the SELECT statement, to satisfy the common need of the database backend that ORDER BY columns be part of the SELECT list when DISTINCT is used. These columns *are not* added to the list of columns actually fetched by the :class:`.Query`, however, so would not affect results. The columns are passed through when using the :attr:`.Query.statement` accessor, however. :param \*expr: optional column expressions. When present, the PostgreSQL dialect will render a ``DISTINCT ON ()`` construct. """ if not expr: self._distinct = True else: expr = self._adapt_col_list(expr) if isinstance(self._distinct, list): self._distinct += expr else: self._distinct = expr @_generative() def prefix_with(self, *prefixes): r"""Apply the prefixes to the query and return the newly resulting ``Query``. :param \*prefixes: optional prefixes, typically strings, not using any commas. In particular is useful for MySQL keywords and optimizer hints: e.g.:: query = sess.query(User.name).\ prefix_with('HIGH_PRIORITY').\ prefix_with('SQL_SMALL_RESULT', 'ALL').\ prefix_with('/*+ BKA(user) */') Would render:: SELECT HIGH_PRIORITY SQL_SMALL_RESULT ALL /*+ BKA(user) */ users.name AS users_name FROM users .. seealso:: :meth:`.HasPrefixes.prefix_with` """ if self._prefixes: self._prefixes += prefixes else: self._prefixes = prefixes @_generative() def suffix_with(self, *suffixes): r"""Apply the suffix to the query and return the newly resulting ``Query``. :param \*suffixes: optional suffixes, typically strings, not using any commas. .. versionadded:: 1.0.0 .. seealso:: :meth:`.Query.prefix_with` :meth:`.HasSuffixes.suffix_with` """ if self._suffixes: self._suffixes += suffixes else: self._suffixes = suffixes def all(self): """Return the results represented by this ``Query`` as a list. This results in an execution of the underlying query. """ return list(self) @_generative(_no_clauseelement_condition) def from_statement(self, statement): """Execute the given SELECT statement and return results. This method bypasses all internal statement compilation, and the statement is executed without modification. The statement is typically either a :func:`~.expression.text` or :func:`~.expression.select` construct, and should return the set of columns appropriate to the entity class represented by this :class:`.Query`. .. seealso:: :ref:`orm_tutorial_literal_sql` - usage examples in the ORM tutorial """ statement = expression._expression_literal_as_text(statement) if not isinstance( statement, (expression.TextClause, expression.SelectBase) ): raise sa_exc.ArgumentError( "from_statement accepts text(), select(), " "and union() objects only." ) self._statement = statement def first(self): """Return the first result of this ``Query`` or None if the result doesn't contain any row. first() applies a limit of one within the generated SQL, so that only one primary entity row is generated on the server side (note this may consist of multiple result rows if join-loaded collections are present). Calling :meth:`.Query.first` results in an execution of the underlying query. .. seealso:: :meth:`.Query.one` :meth:`.Query.one_or_none` """ if self._statement is not None: ret = list(self)[0:1] else: ret = list(self[0:1]) if len(ret) > 0: return ret[0] else: return None def one_or_none(self): """Return at most one result or raise an exception. Returns ``None`` if the query selects no rows. Raises ``sqlalchemy.orm.exc.MultipleResultsFound`` if multiple object identities are returned, or if multiple rows are returned for a query that returns only scalar values as opposed to full identity-mapped entities. Calling :meth:`.Query.one_or_none` results in an execution of the underlying query. .. versionadded:: 1.0.9 Added :meth:`.Query.one_or_none` .. seealso:: :meth:`.Query.first` :meth:`.Query.one` """ ret = list(self) l = len(ret) if l == 1: return ret[0] elif l == 0: return None else: raise orm_exc.MultipleResultsFound( "Multiple rows were found for one_or_none()" ) def one(self): """Return exactly one result or raise an exception. Raises ``sqlalchemy.orm.exc.NoResultFound`` if the query selects no rows. Raises ``sqlalchemy.orm.exc.MultipleResultsFound`` if multiple object identities are returned, or if multiple rows are returned for a query that returns only scalar values as opposed to full identity-mapped entities. Calling :meth:`.one` results in an execution of the underlying query. .. seealso:: :meth:`.Query.first` :meth:`.Query.one_or_none` """ try: ret = self.one_or_none() except orm_exc.MultipleResultsFound: raise orm_exc.MultipleResultsFound( "Multiple rows were found for one()" ) else: if ret is None: raise orm_exc.NoResultFound("No row was found for one()") return ret def scalar(self): """Return the first element of the first result or None if no rows present. If multiple rows are returned, raises MultipleResultsFound. >>> session.query(Item).scalar() >>> session.query(Item.id).scalar() 1 >>> session.query(Item.id).filter(Item.id < 0).scalar() None >>> session.query(Item.id, Item.name).scalar() 1 >>> session.query(func.count(Parent.id)).scalar() 20 This results in an execution of the underlying query. """ try: ret = self.one() if not isinstance(ret, tuple): return ret return ret[0] except orm_exc.NoResultFound: return None def __iter__(self): context = self._compile_context() context.statement.use_labels = True if self._autoflush and not self._populate_existing: self.session._autoflush() return self._execute_and_instances(context) def __str__(self): context = self._compile_context() try: bind = ( self._get_bind_args(context, self.session.get_bind) if self.session else None ) except sa_exc.UnboundExecutionError: bind = None return str(context.statement.compile(bind)) def _connection_from_session(self, **kw): conn = self.session.connection(**kw) if self._execution_options: conn = conn.execution_options(**self._execution_options) return conn def _execute_and_instances(self, querycontext): conn = self._get_bind_args( querycontext, self._connection_from_session, close_with_result=True ) result = conn.execute(querycontext.statement, self._params) return loading.instances(querycontext.query, result, querycontext) def _execute_crud(self, stmt, mapper): conn = self._connection_from_session( mapper=mapper, clause=stmt, close_with_result=True ) return conn.execute(stmt, self._params) def _get_bind_args(self, querycontext, fn, **kw): return fn( mapper=self._bind_mapper(), clause=querycontext.statement, **kw ) @property def column_descriptions(self): """Return metadata about the columns which would be returned by this :class:`.Query`. Format is a list of dictionaries:: user_alias = aliased(User, name='user2') q = sess.query(User, User.id, user_alias) # this expression: q.column_descriptions # would return: [ { 'name':'User', 'type':User, 'aliased':False, 'expr':User, 'entity': User }, { 'name':'id', 'type':Integer(), 'aliased':False, 'expr':User.id, 'entity': User }, { 'name':'user2', 'type':User, 'aliased':True, 'expr':user_alias, 'entity': user_alias } ] """ return [ { "name": ent._label_name, "type": ent.type, "aliased": getattr(insp_ent, "is_aliased_class", False), "expr": ent.expr, "entity": getattr(insp_ent, "entity", None) if ent.entity_zero is not None and not insp_ent.is_clause_element else None, } for ent, insp_ent in [ ( _ent, ( inspect(_ent.entity_zero) if _ent.entity_zero is not None else None ), ) for _ent in self._entities ] ] def instances(self, cursor, __context=None): """Given a ResultProxy cursor as returned by connection.execute(), return an ORM result as an iterator. e.g.:: result = engine.execute("select * from users") for u in session.query(User).instances(result): print u """ context = __context if context is None: context = QueryContext(self) return loading.instances(self, cursor, context) def merge_result(self, iterator, load=True): """Merge a result into this :class:`.Query` object's Session. Given an iterator returned by a :class:`.Query` of the same structure as this one, return an identical iterator of results, with all mapped instances merged into the session using :meth:`.Session.merge`. This is an optimized method which will merge all mapped instances, preserving the structure of the result rows and unmapped columns with less method overhead than that of calling :meth:`.Session.merge` explicitly for each value. The structure of the results is determined based on the column list of this :class:`.Query` - if these do not correspond, unchecked errors will occur. The 'load' argument is the same as that of :meth:`.Session.merge`. For an example of how :meth:`~.Query.merge_result` is used, see the source code for the example :ref:`examples_caching`, where :meth:`~.Query.merge_result` is used to efficiently restore state from a cache back into a target :class:`.Session`. """ return loading.merge_result(self, iterator, load) @property def _select_args(self): return { "limit": self._limit, "offset": self._offset, "distinct": self._distinct, "prefixes": self._prefixes, "suffixes": self._suffixes, "group_by": self._group_by or None, "having": self._having, } @property def _should_nest_selectable(self): kwargs = self._select_args return ( kwargs.get("limit") is not None or kwargs.get("offset") is not None or kwargs.get("distinct", False) ) def exists(self): """A convenience method that turns a query into an EXISTS subquery of the form EXISTS (SELECT 1 FROM ... WHERE ...). e.g.:: q = session.query(User).filter(User.name == 'fred') session.query(q.exists()) Producing SQL similar to:: SELECT EXISTS ( SELECT 1 FROM users WHERE users.name = :name_1 ) AS anon_1 The EXISTS construct is usually used in the WHERE clause:: session.query(User.id).filter(q.exists()).scalar() Note that some databases such as SQL Server don't allow an EXISTS expression to be present in the columns clause of a SELECT. To select a simple boolean value based on the exists as a WHERE, use :func:`.literal`:: from sqlalchemy import literal session.query(literal(True)).filter(q.exists()).scalar() """ # .add_columns() for the case that we are a query().select_from(X), # so that ".statement" can be produced (#2995) but also without # omitting the FROM clause from a query(X) (#2818); # .with_only_columns() after we have a core select() so that # we get just "SELECT 1" without any entities. return sql.exists( self.enable_eagerloads(False) .add_columns("1") .with_labels() .statement.with_only_columns([1]) ) def count(self): r"""Return a count of rows this Query would return. This generates the SQL for this Query as follows:: SELECT count(1) AS count_1 FROM ( SELECT ) AS anon_1 For fine grained control over specific columns to count, to skip the usage of a subquery or otherwise control of the FROM clause, or to use other aggregate functions, use :attr:`~sqlalchemy.sql.expression.func` expressions in conjunction with :meth:`~.Session.query`, i.e.:: from sqlalchemy import func # count User records, without # using a subquery. session.query(func.count(User.id)) # return count of user "id" grouped # by "name" session.query(func.count(User.id)).\ group_by(User.name) from sqlalchemy import distinct # count distinct "name" values session.query(func.count(distinct(User.name))) """ col = sql.func.count(sql.literal_column("*")) return self.from_self(col).scalar() def delete(self, synchronize_session="evaluate"): r"""Perform a bulk delete query. Deletes rows matched by this query from the database. E.g.:: sess.query(User).filter(User.age == 25).\ delete(synchronize_session=False) sess.query(User).filter(User.age == 25).\ delete(synchronize_session='evaluate') .. warning:: The :meth:`.Query.delete` method is a "bulk" operation, which bypasses ORM unit-of-work automation in favor of greater performance. **Please read all caveats and warnings below.** :param synchronize_session: chooses the strategy for the removal of matched objects from the session. Valid values are: ``False`` - don't synchronize the session. This option is the most efficient and is reliable once the session is expired, which typically occurs after a commit(), or explicitly using expire_all(). Before the expiration, objects may still remain in the session which were in fact deleted which can lead to confusing results if they are accessed via get() or already loaded collections. ``'fetch'`` - performs a select query before the delete to find objects that are matched by the delete query and need to be removed from the session. Matched objects are removed from the session. ``'evaluate'`` - Evaluate the query's criteria in Python straight on the objects in the session. If evaluation of the criteria isn't implemented, an error is raised. The expression evaluator currently doesn't account for differing string collations between the database and Python. :return: the count of rows matched as returned by the database's "row count" feature. .. warning:: **Additional Caveats for bulk query deletes** * This method does **not work for joined inheritance mappings**, since the **multiple table deletes are not supported by SQL** as well as that the **join condition of an inheritance mapper is not automatically rendered**. Care must be taken in any multiple-table delete to first accommodate via some other means how the related table will be deleted, as well as to explicitly include the joining condition between those tables, even in mappings where this is normally automatic. E.g. if a class ``Engineer`` subclasses ``Employee``, a DELETE against the ``Employee`` table would look like:: session.query(Engineer).\ filter(Engineer.id == Employee.id).\ filter(Employee.name == 'dilbert').\ delete() However the above SQL will not delete from the Engineer table, unless an ON DELETE CASCADE rule is established in the database to handle it. Short story, **do not use this method for joined inheritance mappings unless you have taken the additional steps to make this feasible**. * The polymorphic identity WHERE criteria is **not** included for single- or joined- table updates - this must be added **manually** even for single table inheritance. * The method does **not** offer in-Python cascading of relationships - it is assumed that ON DELETE CASCADE/SET NULL/etc. is configured for any foreign key references which require it, otherwise the database may emit an integrity violation if foreign key references are being enforced. After the DELETE, dependent objects in the :class:`.Session` which were impacted by an ON DELETE may not contain the current state, or may have been deleted. This issue is resolved once the :class:`.Session` is expired, which normally occurs upon :meth:`.Session.commit` or can be forced by using :meth:`.Session.expire_all`. Accessing an expired object whose row has been deleted will invoke a SELECT to locate the row; when the row is not found, an :class:`~sqlalchemy.orm.exc.ObjectDeletedError` is raised. * The ``'fetch'`` strategy results in an additional SELECT statement emitted and will significantly reduce performance. * The ``'evaluate'`` strategy performs a scan of all matching objects within the :class:`.Session`; if the contents of the :class:`.Session` are expired, such as via a proceeding :meth:`.Session.commit` call, **this will result in SELECT queries emitted for every matching object**. * The :meth:`.MapperEvents.before_delete` and :meth:`.MapperEvents.after_delete` events **are not invoked** from this method. Instead, the :meth:`.SessionEvents.after_bulk_delete` method is provided to act upon a mass DELETE of entity rows. .. seealso:: :meth:`.Query.update` :ref:`inserts_and_updates` - Core SQL tutorial """ delete_op = persistence.BulkDelete.factory(self, synchronize_session) delete_op.exec_() return delete_op.rowcount def update(self, values, synchronize_session="evaluate", update_args=None): r"""Perform a bulk update query. Updates rows matched by this query in the database. E.g.:: sess.query(User).filter(User.age == 25).\ update({User.age: User.age - 10}, synchronize_session=False) sess.query(User).filter(User.age == 25).\ update({"age": User.age - 10}, synchronize_session='evaluate') .. warning:: The :meth:`.Query.update` method is a "bulk" operation, which bypasses ORM unit-of-work automation in favor of greater performance. **Please read all caveats and warnings below.** :param values: a dictionary with attributes names, or alternatively mapped attributes or SQL expressions, as keys, and literal values or sql expressions as values. If :ref:`parameter-ordered mode ` is desired, the values can be passed as a list of 2-tuples; this requires that the :paramref:`~sqlalchemy.sql.expression.update.preserve_parameter_order` flag is passed to the :paramref:`.Query.update.update_args` dictionary as well. .. versionchanged:: 1.0.0 - string names in the values dictionary are now resolved against the mapped entity; previously, these strings were passed as literal column names with no mapper-level translation. :param synchronize_session: chooses the strategy to update the attributes on objects in the session. Valid values are: ``False`` - don't synchronize the session. This option is the most efficient and is reliable once the session is expired, which typically occurs after a commit(), or explicitly using expire_all(). Before the expiration, updated objects may still remain in the session with stale values on their attributes, which can lead to confusing results. ``'fetch'`` - performs a select query before the update to find objects that are matched by the update query. The updated attributes are expired on matched objects. ``'evaluate'`` - Evaluate the Query's criteria in Python straight on the objects in the session. If evaluation of the criteria isn't implemented, an exception is raised. The expression evaluator currently doesn't account for differing string collations between the database and Python. :param update_args: Optional dictionary, if present will be passed to the underlying :func:`.update` construct as the ``**kw`` for the object. May be used to pass dialect-specific arguments such as ``mysql_limit``, as well as other special arguments such as :paramref:`~sqlalchemy.sql.expression.update.preserve_parameter_order`. .. versionadded:: 1.0.0 :return: the count of rows matched as returned by the database's "row count" feature. .. warning:: **Additional Caveats for bulk query updates** * The method does **not** offer in-Python cascading of relationships - it is assumed that ON UPDATE CASCADE is configured for any foreign key references which require it, otherwise the database may emit an integrity violation if foreign key references are being enforced. After the UPDATE, dependent objects in the :class:`.Session` which were impacted by an ON UPDATE CASCADE may not contain the current state; this issue is resolved once the :class:`.Session` is expired, which normally occurs upon :meth:`.Session.commit` or can be forced by using :meth:`.Session.expire_all`. * The ``'fetch'`` strategy results in an additional SELECT statement emitted and will significantly reduce performance. * The ``'evaluate'`` strategy performs a scan of all matching objects within the :class:`.Session`; if the contents of the :class:`.Session` are expired, such as via a proceeding :meth:`.Session.commit` call, **this will result in SELECT queries emitted for every matching object**. * The method supports multiple table updates, as detailed in :ref:`multi_table_updates`, and this behavior does extend to support updates of joined-inheritance and other multiple table mappings. However, the **join condition of an inheritance mapper is not automatically rendered**. Care must be taken in any multiple-table update to explicitly include the joining condition between those tables, even in mappings where this is normally automatic. E.g. if a class ``Engineer`` subclasses ``Employee``, an UPDATE of the ``Engineer`` local table using criteria against the ``Employee`` local table might look like:: session.query(Engineer).\ filter(Engineer.id == Employee.id).\ filter(Employee.name == 'dilbert').\ update({"engineer_type": "programmer"}) * The polymorphic identity WHERE criteria is **not** included for single- or joined- table updates - this must be added **manually**, even for single table inheritance. * The :meth:`.MapperEvents.before_update` and :meth:`.MapperEvents.after_update` events **are not invoked from this method**. Instead, the :meth:`.SessionEvents.after_bulk_update` method is provided to act upon a mass UPDATE of entity rows. .. seealso:: :meth:`.Query.delete` :ref:`inserts_and_updates` - Core SQL tutorial """ update_args = update_args or {} update_op = persistence.BulkUpdate.factory( self, synchronize_session, values, update_args ) update_op.exec_() return update_op.rowcount def _compile_context(self, labels=True): if self.dispatch.before_compile: for fn in self.dispatch.before_compile: new_query = fn(self) if new_query is not None: self = new_query context = QueryContext(self) if context.statement is not None: return context context.labels = labels context._for_update_arg = self._for_update_arg for entity in self._entities: entity.setup_context(self, context) for rec in context.create_eager_joins: strategy = rec[0] strategy(*rec[1:]) if context.from_clause: # "load from explicit FROMs" mode, # i.e. when select_from() or join() is used context.froms = list(context.from_clause) # else "load from discrete FROMs" mode, # i.e. when each _MappedEntity has its own FROM if self._enable_single_crit: self._adjust_for_single_inheritance(context) if not context.primary_columns: if self._only_load_props: raise sa_exc.InvalidRequestError( "No column-based properties specified for " "refresh operation. Use session.expire() " "to reload collections and related items." ) else: raise sa_exc.InvalidRequestError( "Query contains no columns with which to " "SELECT from." ) if context.multi_row_eager_loaders and self._should_nest_selectable: context.statement = self._compound_eager_statement(context) else: context.statement = self._simple_statement(context) return context def _compound_eager_statement(self, context): # for eager joins present and LIMIT/OFFSET/DISTINCT, # wrap the query inside a select, # then append eager joins onto that if context.order_by: order_by_col_expr = sql_util.expand_column_list_from_order_by( context.primary_columns, context.order_by ) else: context.order_by = None order_by_col_expr = [] inner = sql.select( context.primary_columns + order_by_col_expr, context.whereclause, from_obj=context.froms, use_labels=context.labels, # TODO: this order_by is only needed if # LIMIT/OFFSET is present in self._select_args, # else the application on the outside is enough order_by=context.order_by, **self._select_args ) # put FOR UPDATE on the inner query, where MySQL will honor it, # as well as if it has an OF so PostgreSQL can use it. inner._for_update_arg = context._for_update_arg for hint in self._with_hints: inner = inner.with_hint(*hint) if self._correlate: inner = inner.correlate(*self._correlate) inner = inner.alias() equivs = self.__all_equivs() context.adapter = sql_util.ColumnAdapter(inner, equivs) statement = sql.select( [inner] + context.secondary_columns, use_labels=context.labels ) # Oracle however does not allow FOR UPDATE on the subquery, # and the Oracle dialect ignores it, plus for PostgreSQL, MySQL # we expect that all elements of the row are locked, so also put it # on the outside (except in the case of PG when OF is used) if ( context._for_update_arg is not None and context._for_update_arg.of is None ): statement._for_update_arg = context._for_update_arg from_clause = inner for eager_join in context.eager_joins.values(): # EagerLoader places a 'stop_on' attribute on the join, # giving us a marker as to where the "splice point" of # the join should be from_clause = sql_util.splice_joins( from_clause, eager_join, eager_join.stop_on ) statement.append_from(from_clause) if context.order_by: statement.append_order_by( *context.adapter.copy_and_process(context.order_by) ) statement.append_order_by(*context.eager_order_by) return statement def _simple_statement(self, context): if not context.order_by: context.order_by = None if self._distinct is True and context.order_by: context.primary_columns += ( sql_util.expand_column_list_from_order_by )(context.primary_columns, context.order_by) context.froms += tuple(context.eager_joins.values()) statement = sql.select( context.primary_columns + context.secondary_columns, context.whereclause, from_obj=context.froms, use_labels=context.labels, order_by=context.order_by, **self._select_args ) statement._for_update_arg = context._for_update_arg for hint in self._with_hints: statement = statement.with_hint(*hint) if self._correlate: statement = statement.correlate(*self._correlate) if context.eager_order_by: statement.append_order_by(*context.eager_order_by) return statement def _adjust_for_single_inheritance(self, context): """Apply single-table-inheritance filtering. For all distinct single-table-inheritance mappers represented in the columns clause of this query, as well as the "select from entity", add criterion to the WHERE clause of the given QueryContext such that only the appropriate subtypes are selected from the total results. """ search = set(self._mapper_adapter_map.values()) if ( self._select_from_entity and self._select_from_entity not in self._mapper_adapter_map ): insp = inspect(self._select_from_entity) if insp.is_aliased_class: adapter = insp._adapter else: adapter = None search = search.union([(self._select_from_entity, adapter)]) for (ext_info, adapter) in search: if ext_info in self._join_entities: continue single_crit = ext_info.mapper._single_table_criterion if single_crit is not None: if adapter: single_crit = adapter.traverse(single_crit) single_crit = self._adapt_clause(single_crit, False, False) context.whereclause = sql.and_( sql.True_._ifnone(context.whereclause), single_crit ) class LockmodeArg(ForUpdateArg): @classmethod def parse_legacy_query(self, mode): if mode in (None, False): return None if mode == "read": read = True nowait = False elif mode == "update": read = nowait = False elif mode == "update_nowait": nowait = True read = False else: raise sa_exc.ArgumentError( "Unknown with_lockmode argument: %r" % mode ) return LockmodeArg(read=read, nowait=nowait) class _QueryEntity(object): """represent an entity column returned within a Query result.""" def __new__(cls, *args, **kwargs): if cls is _QueryEntity: entity = args[1] if not isinstance(entity, util.string_types) and _is_mapped_class( entity ): cls = _MapperEntity elif isinstance(entity, Bundle): cls = _BundleEntity else: cls = _ColumnEntity return object.__new__(cls) def _clone(self): q = self.__class__.__new__(self.__class__) q.__dict__ = self.__dict__.copy() return q class _MapperEntity(_QueryEntity): """mapper/class/AliasedClass entity""" def __init__(self, query, entity): if not query._primary_entity: query._primary_entity = self query._entities.append(self) query._has_mapper_entities = True self.entities = [entity] self.expr = entity supports_single_entity = True use_id_for_hash = True def setup_entity(self, ext_info, aliased_adapter): self.mapper = ext_info.mapper self.aliased_adapter = aliased_adapter self.selectable = ext_info.selectable self.is_aliased_class = ext_info.is_aliased_class self._with_polymorphic = ext_info.with_polymorphic_mappers self._polymorphic_discriminator = ext_info.polymorphic_on self.entity_zero = ext_info if ext_info.is_aliased_class: self._label_name = self.entity_zero.name else: self._label_name = self.mapper.class_.__name__ self.path = self.entity_zero._path_registry def set_with_polymorphic( self, query, cls_or_mappers, selectable, polymorphic_on ): """Receive an update from a call to query.with_polymorphic(). Note the newer style of using a free standing with_polymporphic() construct doesn't make use of this method. """ if self.is_aliased_class: # TODO: invalidrequest ? raise NotImplementedError( "Can't use with_polymorphic() against " "an Aliased object" ) if cls_or_mappers is None: query._reset_polymorphic_adapter(self.mapper) return mappers, from_obj = self.mapper._with_polymorphic_args( cls_or_mappers, selectable ) self._with_polymorphic = mappers self._polymorphic_discriminator = polymorphic_on self.selectable = from_obj query._mapper_loads_polymorphically_with( self.mapper, sql_util.ColumnAdapter(from_obj, self.mapper._equivalent_columns), ) @property def type(self): return self.mapper.class_ @property def entity_zero_or_selectable(self): return self.entity_zero def corresponds_to(self, entity): return _entity_corresponds_to(self.entity_zero, entity) def adapt_to_selectable(self, query, sel): query._entities.append(self) def _get_entity_clauses(self, query, context): adapter = None if not self.is_aliased_class: if query._polymorphic_adapters: adapter = query._polymorphic_adapters.get(self.mapper, None) else: adapter = self.aliased_adapter if adapter: if query._from_obj_alias: ret = adapter.wrap(query._from_obj_alias) else: ret = adapter else: ret = query._from_obj_alias return ret def row_processor(self, query, context, result): adapter = self._get_entity_clauses(query, context) if context.adapter and adapter: adapter = adapter.wrap(context.adapter) elif not adapter: adapter = context.adapter # polymorphic mappers which have concrete tables in # their hierarchy usually # require row aliasing unconditionally. if not adapter and self.mapper._requires_row_aliasing: adapter = sql_util.ColumnAdapter( self.selectable, self.mapper._equivalent_columns ) if query._primary_entity is self: only_load_props = query._only_load_props refresh_state = context.refresh_state else: only_load_props = refresh_state = None _instance = loading._instance_processor( self.mapper, context, result, self.path, adapter, only_load_props=only_load_props, refresh_state=refresh_state, polymorphic_discriminator=self._polymorphic_discriminator, ) return _instance, self._label_name def setup_context(self, query, context): adapter = self._get_entity_clauses(query, context) # if self._adapted_selectable is None: context.froms += (self.selectable,) if context.order_by is False and self.mapper.order_by: context.order_by = self.mapper.order_by # apply adaptation to the mapper's order_by if needed. if adapter: context.order_by = adapter.adapt_list( util.to_list(context.order_by) ) loading._setup_entity_query( context, self.mapper, self, self.path, adapter, context.primary_columns, with_polymorphic=self._with_polymorphic, only_load_props=query._only_load_props, polymorphic_discriminator=self._polymorphic_discriminator, ) def __str__(self): return str(self.mapper) @inspection._self_inspects class Bundle(InspectionAttr): """A grouping of SQL expressions that are returned by a :class:`.Query` under one namespace. The :class:`.Bundle` essentially allows nesting of the tuple-based results returned by a column-oriented :class:`.Query` object. It also is extensible via simple subclassing, where the primary capability to override is that of how the set of expressions should be returned, allowing post-processing as well as custom return types, without involving ORM identity-mapped classes. .. versionadded:: 0.9.0 .. seealso:: :ref:`bundles` """ single_entity = False """If True, queries for a single Bundle will be returned as a single entity, rather than an element within a keyed tuple.""" is_clause_element = False is_mapper = False is_aliased_class = False def __init__(self, name, *exprs, **kw): r"""Construct a new :class:`.Bundle`. e.g.:: bn = Bundle("mybundle", MyClass.x, MyClass.y) for row in session.query(bn).filter( bn.c.x == 5).filter(bn.c.y == 4): print(row.mybundle.x, row.mybundle.y) :param name: name of the bundle. :param \*exprs: columns or SQL expressions comprising the bundle. :param single_entity=False: if True, rows for this :class:`.Bundle` can be returned as a "single entity" outside of any enclosing tuple in the same manner as a mapped entity. """ self.name = self._label = name self.exprs = exprs self.c = self.columns = ColumnCollection() self.columns.update( (getattr(col, "key", col._label), col) for col in exprs ) self.single_entity = kw.pop("single_entity", self.single_entity) columns = None """A namespace of SQL expressions referred to by this :class:`.Bundle`. e.g.:: bn = Bundle("mybundle", MyClass.x, MyClass.y) q = sess.query(bn).filter(bn.c.x == 5) Nesting of bundles is also supported:: b1 = Bundle("b1", Bundle('b2', MyClass.a, MyClass.b), Bundle('b3', MyClass.x, MyClass.y) ) q = sess.query(b1).filter( b1.c.b2.c.a == 5).filter(b1.c.b3.c.y == 9) .. seealso:: :attr:`.Bundle.c` """ c = None """An alias for :attr:`.Bundle.columns`.""" def _clone(self): cloned = self.__class__.__new__(self.__class__) cloned.__dict__.update(self.__dict__) return cloned def __clause_element__(self): return expression.ClauseList(group=False, *self.exprs) @property def clauses(self): return self.__clause_element__().clauses def label(self, name): """Provide a copy of this :class:`.Bundle` passing a new label.""" cloned = self._clone() cloned.name = name return cloned def create_row_processor(self, query, procs, labels): """Produce the "row processing" function for this :class:`.Bundle`. May be overridden by subclasses. .. seealso:: :ref:`bundles` - includes an example of subclassing. """ keyed_tuple = util.lightweight_named_tuple("result", labels) def proc(row): return keyed_tuple([proc(row) for proc in procs]) return proc class _BundleEntity(_QueryEntity): use_id_for_hash = False def __init__(self, query, bundle, setup_entities=True): query._entities.append(self) self.bundle = self.expr = bundle self.type = type(bundle) self._label_name = bundle.name self._entities = [] if setup_entities: for expr in bundle.exprs: if isinstance(expr, Bundle): _BundleEntity(self, expr) else: _ColumnEntity(self, expr) self.supports_single_entity = self.bundle.single_entity @property def mapper(self): ezero = self.entity_zero if ezero is not None: return ezero.mapper else: return None @property def entities(self): entities = [] for ent in self._entities: entities.extend(ent.entities) return entities @property def entity_zero(self): for ent in self._entities: ezero = ent.entity_zero if ezero is not None: return ezero else: return None def corresponds_to(self, entity): # TODO: we might be able to implement this but for now # we are working around it return False @property def entity_zero_or_selectable(self): for ent in self._entities: ezero = ent.entity_zero_or_selectable if ezero is not None: return ezero else: return None def adapt_to_selectable(self, query, sel): c = _BundleEntity(query, self.bundle, setup_entities=False) # c._label_name = self._label_name # c.entity_zero = self.entity_zero # c.entities = self.entities for ent in self._entities: ent.adapt_to_selectable(c, sel) def setup_entity(self, ext_info, aliased_adapter): for ent in self._entities: ent.setup_entity(ext_info, aliased_adapter) def setup_context(self, query, context): for ent in self._entities: ent.setup_context(query, context) def row_processor(self, query, context, result): procs, labels = zip( *[ ent.row_processor(query, context, result) for ent in self._entities ] ) proc = self.bundle.create_row_processor(query, procs, labels) return proc, self._label_name class _ColumnEntity(_QueryEntity): """Column/expression based entity.""" def __init__(self, query, column, namespace=None): self.expr = column self.namespace = namespace search_entities = True check_column = False if isinstance(column, util.string_types): column = sql.literal_column(column) self._label_name = column.name search_entities = False check_column = True _entity = None elif isinstance( column, (attributes.QueryableAttribute, interfaces.PropComparator) ): _entity = getattr(column, "_parententity", None) if _entity is not None: search_entities = False self._label_name = column.key column = column._query_clause_element() check_column = True if isinstance(column, Bundle): _BundleEntity(query, column) return if not isinstance(column, sql.ColumnElement): if hasattr(column, "_select_iterable"): # break out an object like Table into # individual columns for c in column._select_iterable: if c is column: break _ColumnEntity(query, c, namespace=column) else: return raise sa_exc.InvalidRequestError( "SQL expression, column, or mapped entity " "expected - got '%r'" % (column,) ) elif not check_column: self._label_name = getattr(column, "key", None) search_entities = True self.type = type_ = column.type self.use_id_for_hash = not type_.hashable # If the Column is unnamed, give it a # label() so that mutable column expressions # can be located in the result even # if the expression's identity has been changed # due to adaption. if not column._label and not getattr(column, "is_literal", False): column = column.label(self._label_name) query._entities.append(self) self.column = column self.froms = set() # look for ORM entities represented within the # given expression. Try to count only entities # for columns whose FROM object is in the actual list # of FROMs for the overall expression - this helps # subqueries which were built from ORM constructs from # leaking out their entities into the main select construct self.actual_froms = actual_froms = set(column._from_objects) if not search_entities: self.entity_zero = _entity if _entity: self.entities = [_entity] self.mapper = _entity.mapper else: self.entities = [] self.mapper = None self._from_entities = set(self.entities) else: all_elements = [ elem for elem in sql_util.surface_column_elements( column, include_scalar_selects=False ) if "parententity" in elem._annotations ] self.entities = util.unique_list( [ elem._annotations["parententity"] for elem in all_elements if "parententity" in elem._annotations ] ) self._from_entities = set( [ elem._annotations["parententity"] for elem in all_elements if "parententity" in elem._annotations and actual_froms.intersection(elem._from_objects) ] ) if self.entities: self.entity_zero = self.entities[0] self.mapper = self.entity_zero.mapper elif self.namespace is not None: self.entity_zero = self.namespace self.mapper = None else: self.entity_zero = None self.mapper = None supports_single_entity = False @property def entity_zero_or_selectable(self): if self.entity_zero is not None: return self.entity_zero elif self.actual_froms: return list(self.actual_froms)[0] else: return None def adapt_to_selectable(self, query, sel): c = _ColumnEntity(query, sel.corresponding_column(self.column)) c._label_name = self._label_name c.entity_zero = self.entity_zero c.entities = self.entities def setup_entity(self, ext_info, aliased_adapter): if "selectable" not in self.__dict__: self.selectable = ext_info.selectable if self.actual_froms.intersection(ext_info.selectable._from_objects): self.froms.add(ext_info.selectable) def corresponds_to(self, entity): if self.entity_zero is None: return False elif _is_aliased_class(entity): # TODO: polymorphic subclasses ? return entity is self.entity_zero else: return not _is_aliased_class( self.entity_zero ) and entity.common_parent(self.entity_zero) def row_processor(self, query, context, result): if ("fetch_column", self) in context.attributes: column = context.attributes[("fetch_column", self)] else: column = query._adapt_clause(self.column, False, True) if column._annotations: # annotated columns perform more slowly in compiler and # result due to the __eq__() method, so use deannotated column = column._deannotate() if context.adapter: column = context.adapter.columns[column] getter = result._getter(column) return getter, self._label_name def setup_context(self, query, context): column = query._adapt_clause(self.column, False, True) if column._annotations: # annotated columns perform more slowly in compiler and # result due to the __eq__() method, so use deannotated column = column._deannotate() context.froms += tuple(self.froms) context.primary_columns.append(column) context.attributes[("fetch_column", self)] = column def __str__(self): return str(self.column) class QueryContext(object): __slots__ = ( "multi_row_eager_loaders", "adapter", "froms", "for_update", "query", "session", "autoflush", "populate_existing", "invoke_all_eagers", "version_check", "refresh_state", "primary_columns", "secondary_columns", "eager_order_by", "eager_joins", "create_eager_joins", "propagate_options", "attributes", "statement", "from_clause", "whereclause", "order_by", "labels", "_for_update_arg", "runid", "partials", "post_load_paths", "identity_token", ) def __init__(self, query): if query._statement is not None: if ( isinstance(query._statement, expression.SelectBase) and not query._statement._textual and not query._statement.use_labels ): self.statement = query._statement.apply_labels() else: self.statement = query._statement else: self.statement = None self.from_clause = query._from_obj self.whereclause = query._criterion self.order_by = query._order_by self.multi_row_eager_loaders = False self.adapter = None self.froms = () self.for_update = None self.query = query self.session = query.session self.autoflush = query._autoflush self.populate_existing = query._populate_existing self.invoke_all_eagers = query._invoke_all_eagers self.version_check = query._version_check self.refresh_state = query._refresh_state self.primary_columns = [] self.secondary_columns = [] self.eager_order_by = [] self.eager_joins = {} self.create_eager_joins = [] self.propagate_options = set( o for o in query._with_options if o.propagate_to_loaders ) self.attributes = query._attributes.copy() if self.refresh_state is not None: self.identity_token = query._refresh_identity_token else: self.identity_token = None class AliasOption(interfaces.MapperOption): def __init__(self, alias): r"""Return a :class:`.MapperOption` that will indicate to the :class:`.Query` that the main table has been aliased. This is a seldom-used option to suit the very rare case that :func:`.contains_eager` is being used in conjunction with a user-defined SELECT statement that aliases the parent table. E.g.:: # define an aliased UNION called 'ulist' ulist = users.select(users.c.user_id==7).\ union(users.select(users.c.user_id>7)).\ alias('ulist') # add on an eager load of "addresses" statement = ulist.outerjoin(addresses).\ select().apply_labels() # create query, indicating "ulist" will be an # alias for the main table, "addresses" # property should be eager loaded query = session.query(User).options( contains_alias(ulist), contains_eager(User.addresses)) # then get results via the statement results = query.from_statement(statement).all() :param alias: is the string name of an alias, or a :class:`~.sql.expression.Alias` object representing the alias. """ self.alias = alias def process_query(self, query): if isinstance(self.alias, util.string_types): alias = query._mapper_zero().persist_selectable.alias(self.alias) else: alias = self.alias query._from_obj_alias = sql_util.ColumnAdapter(alias)