SQLAlchemy 2.0 Documentation

create_row_processor(), columns_to_assign, declarative_scan(), do_init(), get_history(), instrument_class(), mapper_property_to_assign

Class signature

class sqlalchemy.orm.ColumnProperty.Comparator (sqlalchemy.util.langhelpers.MemoizedSlots, sqlalchemy.orm.PropComparator)

attribute sqlalchemy.orm.ColumnProperty.Comparator.expressions: Sequence[NamedColumn[Any]]¶

The full sequence of columns referenced by this: attribute, adjusted for any aliasing in progress.

New in version 1.3.17.

method sqlalchemy.orm.ColumnProperty.Comparator.operate(op: OperatorType, *other: Any, **kwargs: Any) → ColumnElement[Any]¶

Operate on an argument.

This is the lowest level of operation, raises NotImplementedError by default.

Overriding this on a subclass can allow common behavior to be applied to all operations. For example, overriding ColumnOperators to apply func.lower() to the left and right side:

class MyComparator(ColumnOperators):
    def operate(self, op, other, **kwargs):
        return op(func.lower(self), func.lower(other), **kwargs)

Parameters:

op¶ – Operator callable.
*other¶ – the ‘other’ side of the operation. Will be a single scalar for most operations.
**kwargs¶ – modifiers. These may be passed by special operators such as ColumnOperators.contains().

method sqlalchemy.orm.ColumnProperty.Comparator.reverse_operate(op: OperatorType, other: Any, **kwargs: Any) → ColumnElement[Any]¶

Reverse operate on an argument.

Usage is the same as operate().

attribute sqlalchemy.orm.ColumnProperty.columns_to_assign¶

method sqlalchemy.orm.ColumnProperty.declarative_scan(decl_scan: _ClassScanMapperConfig, registry: _RegistryType, cls: Type[Any], originating_module: str | None, key: str, mapped_container: Type[Mapped[Any]] | None, annotation: _AnnotationScanType | None, extracted_mapped_annotation: _AnnotationScanType | None, is_dataclass_field: bool) → None¶: Perform class-specific initializaton at early declarative scanning time.

New in version 2.0.

method sqlalchemy.orm.ColumnProperty.do_init() → None¶

Perform subclass-specific initialization post-mapper-creation steps.

This is a template method called by the MapperProperty object’s init() method.

attribute sqlalchemy.orm.ColumnProperty.expression¶

Return the primary column or expression for this ColumnProperty.

E.g.:

class File(Base):
    # ...

    name = Column(String(64))
    extension = Column(String(8))
    filename = column_property(name + '.' + extension)
    path = column_property('C:/' + filename.expression)

method sqlalchemy.orm.ColumnProperty.instrument_class(mapper: Mapper[Any]) → None¶

Hook called by the Mapper to the property to initiate instrumentation of the class attribute managed by this MapperProperty.

The MapperProperty here will typically call out to the attributes module to set up an InstrumentedAttribute.

This step is the first of two steps to set up an InstrumentedAttribute, and is called early in the mapper setup process.

The second step is typically the init_class_attribute step, called from StrategizedProperty via the post_instrument_class() hook. This step assigns additional state to the InstrumentedAttribute (specifically the “impl”) which has been determined after the MapperProperty has determined what kind of persistence management it needs to do (e.g. scalar, object, collection, etc).

attribute sqlalchemy.orm.ColumnProperty.mapper_property_to_assign¶

method sqlalchemy.orm.ColumnProperty.merge(session: Session, source_state: InstanceState[Any], source_dict: _InstanceDict, dest_state: InstanceState[Any], dest_dict: _InstanceDict, load: bool, _recursive: Dict[Any, object], _resolve_conflict_map: Dict[_IdentityKeyType[Any], object]) → None¶: Merge the attribute represented by this MapperProperty from source to destination object.

class sqlalchemy.orm.Composite¶

Declarative-compatible front-end for the CompositeProperty class.

Public constructor is the composite() function.

Changed in version 2.0: Added Composite as a Declarative compatible subclass of CompositeProperty.

See also

Composite Column Types

Class signature

class sqlalchemy.orm.Composite (sqlalchemy.orm.descriptor_props.CompositeProperty, sqlalchemy.orm.base._DeclarativeMapped)

class sqlalchemy.orm.CompositeProperty¶

Defines a “composite” mapped attribute, representing a collection of columns as one attribute.

CompositeProperty is constructed using the composite() function.

See also

Composite Column Types

Members

Class signature

class sqlalchemy.orm.CompositeProperty (sqlalchemy.orm._MapsColumns, sqlalchemy.orm._IntrospectsAnnotations, sqlalchemy.orm.descriptor_props.DescriptorProperty)

class Comparator¶

Produce boolean, comparison, and other operators for Composite attributes.

See the example in Redefining Comparison Operations for Composites for an overview of usage , as well as the documentation for PropComparator.

See also

PropComparator

Mapper.all_orm_descriptors

Class signature

class sqlalchemy.orm.CompositeProperty.Comparator (sqlalchemy.orm.PropComparator)

class CompositeBundle¶

Class signature

class sqlalchemy.orm.CompositeProperty.CompositeBundle (sqlalchemy.orm.Bundle)

method sqlalchemy.orm.CompositeProperty.CompositeBundle.create_row_processor(query: Select[Any], procs: Sequence[Callable[[Row[Any]], Any]], labels: Sequence[str]) → Callable[[Row[Any]], Any]¶

Produce the “row processing” function for this Bundle.

May be overridden by subclasses to provide custom behaviors when results are fetched. The method is passed the statement object and a set of “row processor” functions at query execution time; these processor functions when given a result row will return the individual attribute value, which can then be adapted into any kind of return data structure.

The example below illustrates replacing the usual Row return structure with a straight Python dictionary:

from sqlalchemy.orm import Bundle

class DictBundle(Bundle):
    def create_row_processor(self, query, procs, labels):
        'Override create_row_processor to return values as
        dictionaries'

        def proc(row):
            return dict(
                zip(labels, (proc(row) for proc in procs))
            )
        return proc

A result from the above Bundle will return dictionary values:

bn = DictBundle('mybundle', MyClass.data1, MyClass.data2)
for row in session.execute(select(bn)).where(bn.c.data1 == 'd1'):
    print(row.mybundle['data1'], row.mybundle['data2'])

attribute sqlalchemy.orm.CompositeProperty.columns_to_assign¶

method sqlalchemy.orm.CompositeProperty.declarative_scan(decl_scan: _ClassScanMapperConfig, registry: _RegistryType, cls: Type[Any], originating_module: str | None, key: str, mapped_container: Type[Mapped[Any]] | None, annotation: _AnnotationScanType | None, extracted_mapped_annotation: _AnnotationScanType | None, is_dataclass_field: bool) → None¶: Perform class-specific initializaton at early declarative scanning time.

New in version 2.0.

method sqlalchemy.orm.CompositeProperty.do_init() → None¶: Initialization which occurs after the Composite has been associated with its parent mapper.

method sqlalchemy.orm.CompositeProperty.get_history(state: InstanceState[Any], dict_: _InstanceDict, passive: PassiveFlag = symbol('PASSIVE_OFF')) → History¶: Provided for userland code that uses attributes.get_history().

method sqlalchemy.orm.CompositeProperty.instrument_class(mapper: Mapper[Any]) → None¶

Hook called by the Mapper to the property to initiate instrumentation of the class attribute managed by this MapperProperty.

The MapperProperty here will typically call out to the attributes module to set up an InstrumentedAttribute.

This step is the first of two steps to set up an InstrumentedAttribute, and is called early in the mapper setup process.

The second step is typically the init_class_attribute step, called from StrategizedProperty via the post_instrument_class() hook. This step assigns additional state to the InstrumentedAttribute (specifically the “impl”) which has been determined after the MapperProperty has determined what kind of persistence management it needs to do (e.g. scalar, object, collection, etc).

attribute sqlalchemy.orm.CompositeProperty.mapper_property_to_assign¶

class sqlalchemy.orm.AttributeEventToken¶

A token propagated throughout the course of a chain of attribute events.

Serves as an indicator of the source of the event and also provides a means of controlling propagation across a chain of attribute operations.

The Event object is sent as the initiator argument when dealing with events such as AttributeEvents.append(), AttributeEvents.set(), and AttributeEvents.remove().

The Event object is currently interpreted by the backref event handlers, and is used to control the propagation of operations across two mutually-dependent attributes.

Changed in version 2.0: Changed the name from AttributeEvent to AttributeEventToken.

Attribute impl:: The AttributeImpl which is the current event initiator.
Attribute op:: The symbol OP_APPEND, OP_REMOVE, OP_REPLACE, or OP_BULK_REPLACE, indicating the source operation.

class sqlalchemy.orm.IdentityMap¶

Members

check_modified()

method sqlalchemy.orm.IdentityMap.check_modified() → bool¶: return True if any InstanceStates present have been marked as ‘modified’.

class sqlalchemy.orm.InspectionAttr¶

A base class applied to all ORM objects and attributes that are related to things that can be returned by the inspect() function.

The attributes defined here allow the usage of simple boolean checks to test basic facts about the object returned.

Members

extension_type, is_aliased_class, is_attribute, is_bundle, is_clause_element, is_instance, is_mapper, is_property, is_selectable

While the boolean checks here are basically the same as using the Python isinstance() function, the flags here can be used without the need to import all of these classes, and also such that the SQLAlchemy class system can change while leaving the flags here intact for forwards-compatibility.

attribute sqlalchemy.orm.InspectionAttr.extension_type: InspectionAttrExtensionType = 'not_extension'¶: The extension type, if any. Defaults to NotExtension.NOT_EXTENSION

See also

HybridExtensionType

AssociationProxyExtensionType

attribute sqlalchemy.orm.InspectionAttr.is_aliased_class = False¶: True if this object is an instance of AliasedClass.

attribute sqlalchemy.orm.InspectionAttr.is_attribute = False¶

True if this object is a Python descriptor.

This can refer to one of many types. Usually a QueryableAttribute which handles attributes events on behalf of a MapperProperty. But can also be an extension type such as AssociationProxy or hybrid_property. The InspectionAttr.extension_type will refer to a constant identifying the specific subtype.

See also

attribute sqlalchemy.orm.InspectionAttr.is_bundle = False¶: True if this object is an instance of Bundle.

attribute sqlalchemy.orm.InspectionAttr.is_clause_element = False¶: True if this object is an instance of ClauseElement.

attribute sqlalchemy.orm.InspectionAttr.is_instance = False¶: True if this object is an instance of InstanceState.

attribute sqlalchemy.orm.InspectionAttr.is_mapper = False¶: True if this object is an instance of Mapper.

attribute sqlalchemy.orm.InspectionAttr.is_property = False¶: True if this object is an instance of MapperProperty.

attribute sqlalchemy.orm.InspectionAttr.is_selectable = False¶: Return True if this object is an instance of Selectable.

class sqlalchemy.orm.InspectionAttrInfo¶

Adds the .info attribute to InspectionAttr.

The rationale for InspectionAttr vs. InspectionAttrInfo is that the former is compatible as a mixin for classes that specify __slots__; this is essentially an implementation artifact.

Members

info

Class signature

class sqlalchemy.orm.InspectionAttrInfo (sqlalchemy.orm.base.InspectionAttr)

attribute sqlalchemy.orm.InspectionAttrInfo.info¶

Info dictionary associated with the object, allowing user-defined data to be associated with this InspectionAttr.

The dictionary is generated when first accessed. Alternatively, it can be specified as a constructor argument to the column_property(), relationship(), or composite() functions.

See also

QueryableAttribute.info

Inspection of Mapped Instances

class sqlalchemy.orm.InstanceState¶

Tracks state information at the instance level.

The InstanceState is a key object used by the SQLAlchemy ORM in order to track the state of an object; it is created the moment an object is instantiated, typically as a result of instrumentation which SQLAlchemy applies to the __init__() method of the class.

InstanceState is also a semi-public object, available for runtime inspection as to the state of a mapped instance, including information such as its current status within a particular Session and details about data on individual attributes. The public API in order to acquire a InstanceState object is to use the inspect() system:

>>> from sqlalchemy import inspect
>>> insp = inspect(some_mapped_object)
>>> insp.attrs.nickname.history
History(added=['new nickname'], unchanged=(), deleted=['nickname'])

See also

Class signature

class sqlalchemy.orm.InstanceState (sqlalchemy.orm.base.InspectionAttrInfo, typing.Generic)

attribute sqlalchemy.orm.InstanceState.async_session¶

Return the owning AsyncSession for this instance, or None if none available.

This attribute is only non-None when the sqlalchemy.ext.asyncio API is in use for this ORM object. The returned AsyncSession object will be a proxy for the Session object that would be returned from the InstanceState.session attribute for this InstanceState.

New in version 1.4.18.

See also

Asynchronous I/O (asyncio)

attribute sqlalchemy.orm.InstanceState.attrs¶

Return a namespace representing each attribute on the mapped object, including its current value and history.

The returned object is an instance of AttributeState. This object allows inspection of the current data within an attribute as well as attribute history since the last flush.

attribute sqlalchemy.orm.InstanceState.callables: Dict[str, Callable[[InstanceState[_O], PassiveFlag], Any]] = {}¶

A namespace where a per-state loader callable can be associated.

In SQLAlchemy 1.0, this is only used for lazy loaders / deferred loaders that were set up via query option.

Previously, callables was used also to indicate expired attributes by storing a link to the InstanceState itself in this dictionary. This role is now handled by the expired_attributes set.

attribute sqlalchemy.orm.InstanceState.deleted¶

Return True if the object is deleted.

An object that is in the deleted state is guaranteed to not be within the Session.identity_map of its parent Session; however if the session’s transaction is rolled back, the object will be restored to the persistent state and the identity map.

Note

The InstanceState.deleted attribute refers to a specific state of the object that occurs between the “persistent” and “detached” states; once the object is detached, the InstanceState.deleted attribute no longer returns True; in order to detect that a state was deleted, regardless of whether or not the object is associated with a Session, use the InstanceState.was_deleted accessor.

See also

Quickie Intro to Object States

attribute sqlalchemy.orm.InstanceState.detached¶: Return True if the object is detached.

See also

Quickie Intro to Object States

attribute sqlalchemy.orm.InstanceState.dict¶

Return the instance dict used by the object.

Under normal circumstances, this is always synonymous with the __dict__ attribute of the mapped object, unless an alternative instrumentation system has been configured.

In the case that the actual object has been garbage collected, this accessor returns a blank dictionary.

attribute sqlalchemy.orm.InstanceState.expired: bool = False¶: When True the object is expired.

See also

Refreshing / Expiring

attribute sqlalchemy.orm.InstanceState.expired_attributes: Set[str]¶

The set of keys which are ‘expired’ to be loaded by the manager’s deferred scalar loader, assuming no pending changes.

See also the unmodified collection which is intersected against this set when a refresh operation occurs.

attribute sqlalchemy.orm.InstanceState.has_identity¶

Return True if this object has an identity key.

This should always have the same value as the expression state.persistent or state.detached.

attribute sqlalchemy.orm.InstanceState.identity¶

Return the mapped identity of the mapped object. This is the primary key identity as persisted by the ORM which can always be passed directly to Query.get().

Returns None if the object has no primary key identity.

Note

An object which is transient or pending does not have a mapped identity until it is flushed, even if its attributes include primary key values.

attribute sqlalchemy.orm.InstanceState.identity_key¶

Return the identity key for the mapped object.

This is the key used to locate the object within the Session.identity_map mapping. It contains the identity as returned by identity within it.

attribute sqlalchemy.orm.InstanceState.is_instance: bool = True¶: True if this object is an instance of InstanceState.

attribute sqlalchemy.orm.InstanceState.mapper¶: Return the Mapper used for this mapped object.

attribute sqlalchemy.orm.InstanceState.modified: bool = False¶: When True the object was modified.

attribute sqlalchemy.orm.InstanceState.object¶

Return the mapped object represented by this InstanceState.

Returns None if the object has been garbage collected

attribute sqlalchemy.orm.InstanceState.pending¶: Return True if the object is pending.

See also

Quickie Intro to Object States

attribute sqlalchemy.orm.InstanceState.persistent¶

Return True if the object is persistent.

An object that is in the persistent state is guaranteed to be within the Session.identity_map of its parent Session.

See also

Quickie Intro to Object States

attribute sqlalchemy.orm.InstanceState.session¶

Return the owning Session for this instance, or None if none available.

Note that the result here can in some cases be different from that of obj in session; an object that’s been deleted will report as not in session, however if the transaction is still in progress, this attribute will still refer to that session. Only when the transaction is completed does the object become fully detached under normal circumstances.

See also

InstanceState.async_session

attribute sqlalchemy.orm.InstanceState.transient¶: Return True if the object is transient.

See also

Quickie Intro to Object States

attribute sqlalchemy.orm.InstanceState.unloaded¶

Return the set of keys which do not have a loaded value.

This includes expired attributes and any other attribute that was never populated or modified.

attribute sqlalchemy.orm.InstanceState.unloaded_expirable¶

Synonymous with InstanceState.unloaded.

Deprecated since version 2.0: The InstanceState.unloaded_expirable attribute is deprecated. Please use InstanceState.unloaded.

This attribute was added as an implementation-specific detail at some point and should be considered to be private.

attribute sqlalchemy.orm.InstanceState.unmodified¶: Return the set of keys which have no uncommitted changes

method sqlalchemy.orm.InstanceState.unmodified_intersection(keys: Iterable[str]) → Set[str]¶: Return self.unmodified.intersection(keys).

attribute sqlalchemy.orm.InstanceState.was_deleted¶

Return True if this object is or was previously in the “deleted” state and has not been reverted to persistent.

This flag returns True once the object was deleted in flush. When the object is expunged from the session either explicitly or via transaction commit and enters the “detached” state, this flag will continue to report True.

See also

InstanceState.deleted - refers to the “deleted” state

was_deleted() - standalone function

Quickie Intro to Object States

class sqlalchemy.orm.InstrumentedAttribute¶: Base class for descriptor objects that intercept attribute events on behalf of a MapperProperty object. The actual MapperProperty is accessible via the QueryableAttribute.property attribute.

See also

InstrumentedAttribute

MapperProperty

Mapper.all_orm_descriptors

Mapper.attrs

Class signature

class sqlalchemy.orm.InstrumentedAttribute (sqlalchemy.orm.QueryableAttribute)

class sqlalchemy.orm.LoaderCallableStatus¶

An enumeration.

Members

ATTR_EMPTY, ATTR_WAS_SET, NEVER_SET, NO_VALUE, PASSIVE_CLASS_MISMATCH, PASSIVE_NO_RESULT

Class signature

class sqlalchemy.orm.LoaderCallableStatus (enum.Enum)

attribute sqlalchemy.orm.LoaderCallableStatus.ATTR_EMPTY = 3¶: Symbol used internally to indicate an attribute had no callable.

attribute sqlalchemy.orm.LoaderCallableStatus.ATTR_WAS_SET = 2¶: Symbol returned by a loader callable to indicate the retrieved value, or values, were assigned to their attributes on the target object.

attribute sqlalchemy.orm.LoaderCallableStatus.NEVER_SET = 4¶: Synonymous with NO_VALUE

Changed in version 1.4: NEVER_SET was merged with NO_VALUE

attribute sqlalchemy.orm.LoaderCallableStatus.NO_VALUE = 4¶: Symbol which may be placed as the ‘previous’ value of an attribute, indicating no value was loaded for an attribute when it was modified, and flags indicated we were not to load it.

attribute sqlalchemy.orm.LoaderCallableStatus.PASSIVE_CLASS_MISMATCH = 1¶: Symbol indicating that an object is locally present for a given primary key identity but it is not of the requested class. The return value is therefore None and no SQL should be emitted.

attribute sqlalchemy.orm.LoaderCallableStatus.PASSIVE_NO_RESULT = 0¶: Symbol returned by a loader callable or other attribute/history retrieval operation when a value could not be determined, based on loader callable flags.

class sqlalchemy.orm.Mapped¶

Represent an ORM mapped attribute on a mapped class.

This class represents the complete descriptor interface for any class attribute that will have been instrumented by the ORM Mapper class. Provides appropriate information to type checkers such as pylance and mypy so that ORM-mapped attributes are correctly typed.

The most prominent use of Mapped is in the Declarative Mapping form of Mapper configuration, where used explicitly it drives the configuration of ORM attributes such as mapped_class() and relationship().

See also

Using a Declarative Base Class

Declarative Table with mapped_column()

Tip

The Mapped class represents attributes that are handled directly by the Mapper class. It does not include other Python descriptor classes that are provided as extensions, including Hybrid Attributes and the Association Proxy. While these systems still make use of ORM-specific superclasses and structures, they are not instrumented by the Mapper and instead provide their own functionality when they are accessed on a class.

New in version 1.4.

Class signature

class sqlalchemy.orm.Mapped (sqlalchemy.orm.base.SQLORMExpression, sqlalchemy.orm.base.ORMDescriptor, sqlalchemy.orm.base._MappedAnnotationBase, sqlalchemy.sql.roles.DDLConstraintColumnRole)

class sqlalchemy.orm.MappedColumn¶

Maps a single Column on a class.

MappedColumn is a specialization of the ColumnProperty class and is oriented towards declarative configuration.

To construct MappedColumn objects, use the mapped_column() constructor function.

New in version 2.0.

Class signature

class sqlalchemy.orm.MappedColumn (sqlalchemy.orm._IntrospectsAnnotations, sqlalchemy.orm._MapsColumns, sqlalchemy.orm.base._DeclarativeMapped)

class sqlalchemy.orm.MapperProperty¶

Represent a particular class attribute mapped by Mapper.

The most common occurrences of MapperProperty are the mapped Column, which is represented in a mapping as an instance of ColumnProperty, and a reference to another class produced by relationship(), represented in the mapping as an instance of Relationship.

Members

cascade_iterator(), class_attribute, comparator, create_row_processor(), do_init(), doc, info, init(), instrument_class(), is_property, key, merge(), parent, post_instrument_class(), set_parent(), setup()

Class signature

class sqlalchemy.orm.MapperProperty (sqlalchemy.sql.cache_key.HasCacheKey, sqlalchemy.orm._DCAttributeOptions, sqlalchemy.orm.base._MappedAttribute, sqlalchemy.orm.base.InspectionAttrInfo, sqlalchemy.util.langhelpers.MemoizedSlots)

method sqlalchemy.orm.MapperProperty.cascade_iterator(type_: str, state: InstanceState[Any], dict_: _InstanceDict, visited_states: Set[InstanceState[Any]], halt_on: Callable[[InstanceState[Any]], bool] | None = None) → Iterator[Tuple[object, Mapper[Any], InstanceState[Any], _InstanceDict]]¶

Iterate through instances related to the given instance for a particular ‘cascade’, starting with this MapperProperty.

Return an iterator3-tuples (instance, mapper, state).

Note that the ‘cascade’ collection on this MapperProperty is checked first for the given type before cascade_iterator is called.

This method typically only applies to Relationship.

attribute sqlalchemy.orm.MapperProperty.class_attribute¶

Return the class-bound descriptor corresponding to this MapperProperty.

This is basically a getattr() call:

return getattr(self.parent.class_, self.key)

I.e. if this MapperProperty were named addresses, and the class to which it is mapped is User, this sequence is possible:

>>> from sqlalchemy import inspect
>>> mapper = inspect(User)
>>> addresses_property = mapper.attrs.addresses
>>> addresses_property.class_attribute is User.addresses
True
>>> User.addresses.property is addresses_property
True

attribute sqlalchemy.orm.MapperProperty.comparator: PropComparator[_T]¶: The PropComparator instance that implements SQL expression construction on behalf of this mapped attribute.

method sqlalchemy.orm.MapperProperty.create_row_processor(context: ORMCompileState, query_entity: _MapperEntity, path: AbstractEntityRegistry, mapper: Mapper[Any], result: Result[Any], adapter: ORMAdapter | None, populators: _PopulatorDict) → None¶: Produce row processing functions and append to the given set of populators lists.

method sqlalchemy.orm.MapperProperty.do_init() → None¶

Perform subclass-specific initialization post-mapper-creation steps.

This is a template method called by the MapperProperty object’s init() method.

attribute sqlalchemy.orm.MapperProperty.doc: str | None¶: optional documentation string

attribute sqlalchemy.orm.MapperProperty.info: _InfoType¶

Info dictionary associated with the object, allowing user-defined data to be associated with this InspectionAttr.

The dictionary is generated when first accessed. Alternatively, it can be specified as a constructor argument to the column_property(), relationship(), or composite() functions.

See also

QueryableAttribute.info

method sqlalchemy.orm.MapperProperty.init() → None¶: Called after all mappers are created to assemble relationships between mappers and perform other post-mapper-creation initialization steps.

method sqlalchemy.orm.MapperProperty.instrument_class(mapper: Mapper[Any]) → None¶

Hook called by the Mapper to the property to initiate instrumentation of the class attribute managed by this MapperProperty.

The MapperProperty here will typically call out to the attributes module to set up an InstrumentedAttribute.

This step is the first of two steps to set up an InstrumentedAttribute, and is called early in the mapper setup process.

The second step is typically the init_class_attribute step, called from StrategizedProperty via the post_instrument_class() hook. This step assigns additional state to the InstrumentedAttribute (specifically the “impl”) which has been determined after the MapperProperty has determined what kind of persistence management it needs to do (e.g. scalar, object, collection, etc).

attribute sqlalchemy.orm.MapperProperty.is_property = True¶: Part of the InspectionAttr interface; states this object is a mapper property.

attribute sqlalchemy.orm.MapperProperty.key: str¶: name of class attribute

method sqlalchemy.orm.MapperProperty.merge(session: Session, source_state: InstanceState[Any], source_dict: _InstanceDict, dest_state: InstanceState[Any], dest_dict: _InstanceDict, load: bool, _recursive: Dict[Any, object], _resolve_conflict_map: Dict[_IdentityKeyType[Any], object]) → None¶: Merge the attribute represented by this MapperProperty from source to destination object.

attribute sqlalchemy.orm.MapperProperty.parent: Mapper[Any]¶: the Mapper managing this property.

method sqlalchemy.orm.MapperProperty.post_instrument_class(mapper: Mapper[Any]) → None¶

Perform instrumentation adjustments that need to occur after init() has completed.

The given Mapper is the Mapper invoking the operation, which may not be the same Mapper as self.parent in an inheritance scenario; however, Mapper will always at least be a sub-mapper of self.parent.

This method is typically used by StrategizedProperty, which delegates it to LoaderStrategy.init_class_attribute() to perform final setup on the class-bound InstrumentedAttribute.

method sqlalchemy.orm.MapperProperty.set_parent(parent: Mapper[Any], init: bool) → None¶

Set the parent mapper that references this MapperProperty.

This method is overridden by some subclasses to perform extra setup when the mapper is first known.

method sqlalchemy.orm.MapperProperty.setup(context: ORMCompileState, query_entity: _MapperEntity, path: AbstractEntityRegistry, adapter: ORMAdapter | None, **kwargs: Any) → None¶

Called by Query for the purposes of constructing a SQL statement.

Each MapperProperty associated with the target mapper processes the statement referenced by the query context, adding columns and/or criterion as appropriate.

class sqlalchemy.orm.MappedSQLExpression¶

Declarative front-end for the ColumnProperty class.

Public constructor is the column_property() function.

Changed in version 2.0: Added MappedSQLExpression as a Declarative compatible subclass for ColumnProperty.

See also

MappedColumn

Class signature

class sqlalchemy.orm.MappedSQLExpression (sqlalchemy.orm.properties.ColumnProperty, sqlalchemy.orm.base._DeclarativeMapped)

class sqlalchemy.orm.InspectionAttrExtensionType¶: Symbols indicating the type of extension that a InspectionAttr is part of.

Class signature

class sqlalchemy.orm.InspectionAttrExtensionType (enum.Enum)

class sqlalchemy.orm.NotExtension¶

An enumeration.

Members

NOT_EXTENSION

Class signature

class sqlalchemy.orm.NotExtension (sqlalchemy.orm.base.InspectionAttrExtensionType)

attribute sqlalchemy.orm.NotExtension.NOT_EXTENSION = 'not_extension'¶

Symbol indicating an InspectionAttr that’s not part of sqlalchemy.ext.

Is assigned to the InspectionAttr.extension_type attribute.

function sqlalchemy.orm.merge_result(query: Query[Any], iterator: FrozenResult | Iterable[Sequence[Any]] | Iterable[object], load: bool = True) → FrozenResult | Iterable[Any]¶

Merge a result into the given Query object’s Session.

Deprecated since version 2.0: The merge_result() function is considered legacy as of the 1.x series of SQLAlchemy and becomes a legacy construct in 2.0. The function as well as the method on Query is superseded by the merge_frozen_result() function. (Background on SQLAlchemy 2.0 at: SQLAlchemy 2.0 - Major Migration Guide)

See Query.merge_result() for top-level documentation on this function.

function sqlalchemy.orm.merge_frozen_result(session, statement, frozen_result, load=True)¶

Merge a FrozenResult back into a Session, returning a new Result object with persistent objects.

See the section Re-Executing Statements for an example.

See also

Re-Executing Statements

Result.freeze()

FrozenResult

class sqlalchemy.orm.PropComparator¶

Defines SQL operations for ORM mapped attributes.

SQLAlchemy allows for operators to be redefined at both the Core and ORM level. PropComparator is the base class of operator redefinition for ORM-level operations, including those of ColumnProperty, Relationship, and Composite.

User-defined subclasses of PropComparator may be created. The built-in Python comparison and math operator methods, such as ColumnOperators.__eq__(), ColumnOperators.__lt__(), and ColumnOperators.__add__(), can be overridden to provide new operator behavior. The custom PropComparator is passed to the MapperProperty instance via the comparator_factory argument. In each case, the appropriate subclass of PropComparator should be used:

# definition of custom PropComparator subclasses

from sqlalchemy.orm.properties import \
                        ColumnProperty,\
                        Composite,\
                        Relationship

class MyColumnComparator(ColumnProperty.Comparator):
    def __eq__(self, other):
        return self.__clause_element__() == other

class MyRelationshipComparator(Relationship.Comparator):
    def any(self, expression):
        "define the 'any' operation"
        # ...

class MyCompositeComparator(Composite.Comparator):
    def __gt__(self, other):
        "redefine the 'greater than' operation"

        return sql.and_(*[a>b for a, b in
                          zip(self.__clause_element__().clauses,
                              other.__composite_values__())])


# application of custom PropComparator subclasses

from sqlalchemy.orm import column_property, relationship, composite
from sqlalchemy import Column, String

class SomeMappedClass(Base):
    some_column = column_property(Column("some_column", String),
                        comparator_factory=MyColumnComparator)

    some_relationship = relationship(SomeOtherClass,
                        comparator_factory=MyRelationshipComparator)

    some_composite = composite(
            Column("a", String), Column("b", String),
            comparator_factory=MyCompositeComparator
        )

Note that for column-level operator redefinition, it’s usually simpler to define the operators at the Core level, using the TypeEngine.comparator_factory attribute. See Redefining and Creating New Operators for more detail.

See also

Comparator

Adding Criteria to loader options

Class signature

class sqlalchemy.orm.PropComparator (sqlalchemy.orm.base.SQLORMOperations, typing.Generic, sqlalchemy.sql.expression.ColumnOperators)

method sqlalchemy.orm.PropComparator.__eq__(other: Any) → ColumnOperators¶

inherited from the sqlalchemy.sql.expression.ColumnOperators.__eq__ method of ColumnOperators

Implement the == operator.

In a column context, produces the clause a = b. If the target is None, produces a IS NULL.

method sqlalchemy.orm.PropComparator.__le__(other: Any) → ColumnOperators¶

inherited from the sqlalchemy.sql.expression.ColumnOperators.__le__ method of ColumnOperators

Implement the <= operator.

In a column context, produces the clause a <= b.

method sqlalchemy.orm.PropComparator.__lt__(other: Any) → ColumnOperators¶

inherited from the sqlalchemy.sql.expression.ColumnOperators.__lt__ method of ColumnOperators

Implement the < operator.

In a column context, produces the clause a < b.

method sqlalchemy.orm.PropComparator.__ne__(other: Any) → ColumnOperators¶

inherited from the sqlalchemy.sql.expression.ColumnOperators.__ne__ method of ColumnOperators

Implement the != operator.

In a column context, produces the clause a != b. If the target is None, produces a IS NOT NULL.

method sqlalchemy.orm.PropComparator.adapt_to_entity(adapt_to_entity: AliasedInsp[Any]) → PropComparator[_T_co]¶: Return a copy of this PropComparator which will use the given AliasedInsp to produce corresponding expressions.

attribute sqlalchemy.orm.PropComparator.adapter¶: Produce a callable that adapts column expressions to suit an aliased version of this comparator.

method sqlalchemy.orm.PropComparator.all_() → ColumnOperators¶

inherited from the ColumnOperators.all_() method of ColumnOperators

Produce an all_() clause against the parent object.

See the documentation for all_() for examples.

Note

be sure to not confuse the newer ColumnOperators.all_() method with the legacy version of this method, the Comparator.all() method that’s specific to ARRAY, which uses a different calling style.

method sqlalchemy.orm.PropComparator.and_(*criteria: _ColumnExpressionArgument[bool]) → PropComparator[bool]¶

Add additional criteria to the ON clause that’s represented by this relationship attribute.

E.g.:

stmt = select(User).join(
    User.addresses.and_(Address.email_address != 'foo')
)

stmt = select(User).options(
    joinedload(User.addresses.and_(Address.email_address != 'foo'))
)

New in version 1.4.

with_loader_criteria()

method sqlalchemy.orm.PropComparator.any(criterion: _ColumnExpressionArgument[bool] | None = None, **kwargs: Any) → ColumnElement[bool]¶

Return a SQL expression representing true if this element references a member which meets the given criterion.

The usual implementation of any() is Comparator.any().

Parameters:

criterion¶ – an optional ClauseElement formulated against the member class’ table or attributes.
**kwargs¶ – key/value pairs corresponding to member class attribute names which will be compared via equality to the corresponding values.

method sqlalchemy.orm.PropComparator.any_() → ColumnOperators¶

inherited from the ColumnOperators.any_() method of ColumnOperators

Produce an any_() clause against the parent object.

See the documentation for any_() for examples.

Note

be sure to not confuse the newer ColumnOperators.any_() method with the legacy version of this method, the Comparator.any() method that’s specific to ARRAY, which uses a different calling style.

method sqlalchemy.orm.PropComparator.asc() → ColumnOperators¶: inherited from the ColumnOperators.asc() method of ColumnOperators

Produce a asc() clause against the parent object.

method sqlalchemy.orm.PropComparator.between(cleft: Any, cright: Any, symmetric: bool = False) → ColumnOperators¶: inherited from the ColumnOperators.between() method of ColumnOperators

Produce a between() clause against the parent object, given the lower and upper range.

method sqlalchemy.orm.PropComparator.bitwise_and(other: Any) → ColumnOperators¶: inherited from the ColumnOperators.bitwise_and() method of ColumnOperators

Produce a bitwise AND operation, typically via the & operator.

New in version 2.0.2.

See also

Bitwise Operators

method sqlalchemy.orm.PropComparator.bitwise_lshift(other: Any) → ColumnOperators¶: inherited from the ColumnOperators.bitwise_lshift() method of ColumnOperators

Produce a bitwise LSHIFT operation, typically via the << operator.

New in version 2.0.2.

See also

Bitwise Operators

method sqlalchemy.orm.PropComparator.bitwise_not() → ColumnOperators¶: inherited from the ColumnOperators.bitwise_not() method of ColumnOperators

Produce a bitwise NOT operation, typically via the ~ operator.

New in version 2.0.2.

See also

Bitwise Operators

method sqlalchemy.orm.PropComparator.bitwise_or(other: Any) → ColumnOperators¶: inherited from the ColumnOperators.bitwise_or() method of ColumnOperators

Produce a bitwise OR operation, typically via the | operator.

New in version 2.0.2.

See also

Bitwise Operators

method sqlalchemy.orm.PropComparator.bitwise_rshift(other: Any) → ColumnOperators¶: inherited from the ColumnOperators.bitwise_rshift() method of ColumnOperators

Produce a bitwise RSHIFT operation, typically via the >> operator.

New in version 2.0.2.

See also

Bitwise Operators

method sqlalchemy.orm.PropComparator.bitwise_xor(other: Any) → ColumnOperators¶: inherited from the ColumnOperators.bitwise_xor() method of ColumnOperators

Produce a bitwise XOR operation, typically via the ^ operator, or # for PostgreSQL.

New in version 2.0.2.

See also

Bitwise Operators

method sqlalchemy.orm.PropComparator.bool_op(opstring: str, precedence: int = 0, python_impl: Callable[[...], Any] | None = None) → Callable[[Any], Operators]¶

inherited from the Operators.bool_op() method of Operators

Return a custom boolean operator.

This method is shorthand for calling Operators.op() and passing the Operators.op.is_comparison flag with True. A key advantage to using Operators.bool_op() is that when using column constructs, the “boolean” nature of the returned expression will be present for PEP 484 purposes.

See also

Operators.op()

method sqlalchemy.orm.PropComparator.collate(collation: str) → ColumnOperators¶: inherited from the ColumnOperators.collate() method of ColumnOperators

Produce a collate() clause against the parent object, given the collation string.

See also

collate()

method sqlalchemy.orm.PropComparator.concat(other: Any) → ColumnOperators¶

inherited from the ColumnOperators.concat() method of ColumnOperators

Implement the ‘concat’ operator.

In a column context, produces the clause a || b, or uses the concat() operator on MySQL.

method sqlalchemy.orm.PropComparator.contains(other: Any, **kw: Any) → ColumnOperators¶

inherited from the ColumnOperators.contains() method of ColumnOperators

Implement the ‘contains’ operator.

Produces a LIKE expression that tests against a match for the middle of a string value:

column LIKE '%' || <other> || '%'

E.g.:

stmt = select(sometable).\
    where(sometable.c.column.contains("foobar"))

Since the operator uses LIKE, wildcard characters "%" and "_" that are present inside the <other> expression will behave like wildcards as well. For literal string values, the ColumnOperators.contains.autoescape flag may be set to True to apply escaping to occurrences of these characters within the string value so that they match as themselves and not as wildcard characters. Alternatively, the ColumnOperators.contains.escape parameter will establish a given character as an escape character which can be of use when the target expression is not a literal string.

Parameters:

other¶ – expression to be compared. This is usually a plain string value, but can also be an arbitrary SQL expression. LIKE wildcard characters % and _ are not escaped by default unless the ColumnOperators.contains.autoescape flag is set to True.
autoescape¶ –
boolean; when True, establishes an escape character within the LIKE expression, then applies it to all occurrences of "%", "_" and the escape character itself within the comparison value, which is assumed to be a literal string and not a SQL expression.

An expression such as:
```
somecolumn.contains("foo%bar", autoescape=True)
```
Will render as:
```
somecolumn LIKE '%' || :param || '%' ESCAPE '/'
```
With the value of :param as "foo/%bar".
escape¶ –
a character which when given will render with the ESCAPE keyword to establish that character as the escape character. This character can then be placed preceding occurrences of % and _ to allow them to act as themselves and not wildcard characters.

An expression such as:
```
somecolumn.contains("foo/%bar", escape="^")
```
Will render as:
```
somecolumn LIKE '%' || :param || '%' ESCAPE '^'
```
The parameter may also be combined with ColumnOperators.contains.autoescape:
```
somecolumn.contains("foo%bar^bat", escape="^", autoescape=True)
```
Where above, the given literal parameter will be converted to "foo^%bar^^bat" before being passed to the database.

See also

ColumnOperators.startswith()

ColumnOperators.endswith()

ColumnOperators.startswith()

method sqlalchemy.orm.PropComparator.desc() → ColumnOperators¶: inherited from the ColumnOperators.desc() method of ColumnOperators

Produce a desc() clause against the parent object.

method sqlalchemy.orm.PropComparator.distinct() → ColumnOperators¶: inherited from the ColumnOperators.distinct() method of ColumnOperators

Produce a distinct() clause against the parent object.

method sqlalchemy.orm.PropComparator.endswith(other: Any, escape: str | None = None, autoescape: bool = False) → ColumnOperators¶

inherited from the ColumnOperators.endswith() method of ColumnOperators

Implement the ‘endswith’ operator.

Produces a LIKE expression that tests against a match for the end of a string value:

column LIKE '%' || <other>

E.g.:

stmt = select(sometable).\
    where(sometable.c.column.endswith("foobar"))

Since the operator uses LIKE, wildcard characters "%" and "_" that are present inside the <other> expression will behave like wildcards as well. For literal string values, the ColumnOperators.endswith.autoescape flag may be set to True to apply escaping to occurrences of these characters within the string value so that they match as themselves and not as wildcard characters. Alternatively, the ColumnOperators.endswith.escape parameter will establish a given character as an escape character which can be of use when the target expression is not a literal string.

Parameters:

other¶ – expression to be compared. This is usually a plain string value, but can also be an arbitrary SQL expression. LIKE wildcard characters % and _ are not escaped by default unless the ColumnOperators.endswith.autoescape flag is set to True.
autoescape¶ –
boolean; when True, establishes an escape character within the LIKE expression, then applies it to all occurrences of "%", "_" and the escape character itself within the comparison value, which is assumed to be a literal string and not a SQL expression.

An expression such as:
```
somecolumn.endswith("foo%bar", autoescape=True)
```
Will render as:
```
somecolumn LIKE '%' || :param ESCAPE '/'
```
With the value of :param as "foo/%bar".
escape¶ –
a character which when given will render with the ESCAPE keyword to establish that character as the escape character. This character can then be placed preceding occurrences of % and _ to allow them to act as themselves and not wildcard characters.

An expression such as:
```
somecolumn.endswith("foo/%bar", escape="^")
```
Will render as:
```
somecolumn LIKE '%' || :param ESCAPE '^'
```
The parameter may also be combined with ColumnOperators.endswith.autoescape:
```
somecolumn.endswith("foo%bar^bat", escape="^", autoescape=True)
```
Where above, the given literal parameter will be converted to "foo^%bar^^bat" before being passed to the database.

See also

ColumnOperators.contains()

ColumnOperators.contains()

method sqlalchemy.orm.PropComparator.has(criterion: _ColumnExpressionArgument[bool] | None = None, **kwargs: Any) → ColumnElement[bool]¶

Return a SQL expression representing true if this element references a member which meets the given criterion.

The usual implementation of has() is Comparator.has().

Parameters:

criterion¶ – an optional ClauseElement formulated against the member class’ table or attributes.
**kwargs¶ – key/value pairs corresponding to member class attribute names which will be compared via equality to the corresponding values.

method sqlalchemy.orm.PropComparator.icontains(other: Any, **kw: Any) → ColumnOperators¶

inherited from the ColumnOperators.icontains() method of ColumnOperators

Implement the icontains operator, e.g. case insensitive version of ColumnOperators.contains().

Produces a LIKE expression that tests against an insensitive match for the middle of a string value:

lower(column) LIKE '%' || lower(<other>) || '%'

E.g.:

stmt = select(sometable).\
    where(sometable.c.column.icontains("foobar"))

Since the operator uses LIKE, wildcard characters "%" and "_" that are present inside the <other> expression will behave like wildcards as well. For literal string values, the ColumnOperators.icontains.autoescape flag may be set to True to apply escaping to occurrences of these characters within the string value so that they match as themselves and not as wildcard characters. Alternatively, the ColumnOperators.icontains.escape parameter will establish a given character as an escape character which can be of use when the target expression is not a literal string.

Parameters:

other¶ – expression to be compared. This is usually a plain string value, but can also be an arbitrary SQL expression. LIKE wildcard characters % and _ are not escaped by default unless the ColumnOperators.icontains.autoescape flag is set to True.
autoescape¶ –
boolean; when True, establishes an escape character within the LIKE expression, then applies it to all occurrences of "%", "_" and the escape character itself within the comparison value, which is assumed to be a literal string and not a SQL expression.

An expression such as:
```
somecolumn.icontains("foo%bar", autoescape=True)
```
Will render as:
```
lower(somecolumn) LIKE '%' || lower(:param) || '%' ESCAPE '/'
```
With the value of :param as "foo/%bar".
escape¶ –
a character which when given will render with the ESCAPE keyword to establish that character as the escape character. This character can then be placed preceding occurrences of % and _ to allow them to act as themselves and not wildcard characters.

An expression such as:
```
somecolumn.icontains("foo/%bar", escape="^")
```
Will render as:
```
lower(somecolumn) LIKE '%' || lower(:param) || '%' ESCAPE '^'
```
The parameter may also be combined with ColumnOperators.contains.autoescape:
```
somecolumn.icontains("foo%bar^bat", escape="^", autoescape=True)
```
Where above, the given literal parameter will be converted to "foo^%bar^^bat" before being passed to the database.

See also

method sqlalchemy.orm.PropComparator.iendswith(other: Any, escape: str | None = None, autoescape: bool = False) → ColumnOperators¶

inherited from the ColumnOperators.iendswith() method of ColumnOperators

Implement the iendswith operator, e.g. case insensitive version of ColumnOperators.endswith().

Produces a LIKE expression that tests against an insensitive match for the end of a string value:

lower(column) LIKE '%' || lower(<other>)

E.g.:

stmt = select(sometable).\
    where(sometable.c.column.iendswith("foobar"))

Since the operator uses LIKE, wildcard characters "%" and "_" that are present inside the <other> expression will behave like wildcards as well. For literal string values, the ColumnOperators.iendswith.autoescape flag may be set to True to apply escaping to occurrences of these characters within the string value so that they match as themselves and not as wildcard characters. Alternatively, the ColumnOperators.iendswith.escape parameter will establish a given character as an escape character which can be of use when the target expression is not a literal string.

Parameters:

other¶ – expression to be compared. This is usually a plain string value, but can also be an arbitrary SQL expression. LIKE wildcard characters % and _ are not escaped by default unless the ColumnOperators.iendswith.autoescape flag is set to True.
autoescape¶ –
boolean; when True, establishes an escape character within the LIKE expression, then applies it to all occurrences of "%", "_" and the escape character itself within the comparison value, which is assumed to be a literal string and not a SQL expression.

An expression such as:
```
somecolumn.iendswith("foo%bar", autoescape=True)
```
Will render as:
```
lower(somecolumn) LIKE '%' || lower(:param) ESCAPE '/'
```
With the value of :param as "foo/%bar".
escape¶ –
a character which when given will render with the ESCAPE keyword to establish that character as the escape character. This character can then be placed preceding occurrences of % and _ to allow them to act as themselves and not wildcard characters.

An expression such as:
```
somecolumn.iendswith("foo/%bar", escape="^")
```
Will render as:
```
lower(somecolumn) LIKE '%' || lower(:param) ESCAPE '^'
```
The parameter may also be combined with ColumnOperators.iendswith.autoescape:
```
somecolumn.endswith("foo%bar^bat", escape="^", autoescape=True)
```
Where above, the given literal parameter will be converted to "foo^%bar^^bat" before being passed to the database.

See also

ColumnOperators.endswith()

method sqlalchemy.orm.PropComparator.ilike(other: Any, escape: str | None = None) → ColumnOperators¶

inherited from the ColumnOperators.ilike() method of ColumnOperators

Implement the ilike operator, e.g. case insensitive LIKE.

In a column context, produces an expression either of the form:

lower(a) LIKE lower(other)

Or on backends that support the ILIKE operator:

a ILIKE other

E.g.:

stmt = select(sometable).\
    where(sometable.c.column.ilike("%foobar%"))

Parameters:

other¶ – expression to be compared
escape¶ –
optional escape character, renders the ESCAPE keyword, e.g.:
```
somecolumn.ilike("foo/%bar", escape="/")
```

See also

ColumnOperators.is_not()

method sqlalchemy.orm.PropComparator.in_(other: Any) → ColumnOperators¶

inherited from the ColumnOperators.in_() method of ColumnOperators

Implement the in operator.

In a column context, produces the clause column IN <other>.

The given parameter other may be:

A list of literal values, e.g.:
```
stmt.where(column.in_([1, 2, 3]))
```
In this calling form, the list of items is converted to a set of bound parameters the same length as the list given:
```
WHERE COL IN (?, ?, ?)
```

A list of tuples may be provided if the comparison is against a tuple_() containing multiple expressions:

from sqlalchemy import tuple_
stmt.where(tuple_(col1, col2).in_([(1, 10), (2, 20), (3, 30)]))

An empty list, e.g.:
```
stmt.where(column.in_([]))
```
In this calling form, the expression renders an “empty set” expression. These expressions are tailored to individual backends and are generally trying to get an empty SELECT statement as a subquery. Such as on SQLite, the expression is:
```
WHERE col IN (SELECT 1 FROM (SELECT 1) WHERE 1!=1)
```
Changed in version 1.4: empty IN expressions now use an execution-time generated SELECT subquery in all cases.
A bound parameter, e.g. bindparam(), may be used if it includes the bindparam.expanding flag:
```
stmt.where(column.in_(bindparam('value', expanding=True)))
```
In this calling form, the expression renders a special non-SQL placeholder expression that looks like:
```
WHERE COL IN ([EXPANDING_value])
```
This placeholder expression is intercepted at statement execution time to be converted into the variable number of bound parameter form illustrated earlier. If the statement were executed as:
```
connection.execute(stmt, {"value": [1, 2, 3]})
```
The database would be passed a bound parameter for each value:
```
WHERE COL IN (?, ?, ?)
```
New in version 1.2: added “expanding” bound parameters

If an empty list is passed, a special “empty list” expression, which is specific to the database in use, is rendered. On SQLite this would be:
```
WHERE COL IN (SELECT 1 FROM (SELECT 1) WHERE 1!=1)
```
New in version 1.3: “expanding” bound parameters now support empty lists

a select() construct, which is usually a correlated scalar select:

stmt.where(
    column.in_(
        select(othertable.c.y).
        where(table.c.x == othertable.c.x)
    )
)

In this calling form, ColumnOperators.in_() renders as given:

WHERE COL IN (SELECT othertable.y
FROM othertable WHERE othertable.x = table.x)

Parameters:: other¶ – a list of literals, a select() construct, or a bindparam() construct that includes the bindparam.expanding flag set to True.

method sqlalchemy.orm.PropComparator.is_(other: Any) → ColumnOperators¶

inherited from the ColumnOperators.is_() method of ColumnOperators

Implement the IS operator.

Normally, IS is generated automatically when comparing to a value of None, which resolves to NULL. However, explicit usage of IS may be desirable if comparing to boolean values on certain platforms.

See also

method sqlalchemy.orm.PropComparator.is_distinct_from(other: Any) → ColumnOperators¶

inherited from the ColumnOperators.is_distinct_from() method of ColumnOperators

Implement the IS DISTINCT FROM operator.

Renders “a IS DISTINCT FROM b” on most platforms; on some such as SQLite may render “a IS NOT b”.

method sqlalchemy.orm.PropComparator.is_not(other: Any) → ColumnOperators¶

inherited from the ColumnOperators.is_not() method of ColumnOperators

Implement the IS NOT operator.

Normally, IS NOT is generated automatically when comparing to a value of None, which resolves to NULL. However, explicit usage of IS NOT may be desirable if comparing to boolean values on certain platforms.

Changed in version 1.4: The is_not() operator is renamed from isnot() in previous releases. The previous name remains available for backwards compatibility.

See also

ColumnOperators.is_()

method sqlalchemy.orm.PropComparator.is_not_distinct_from(other: Any) → ColumnOperators¶

inherited from the ColumnOperators.is_not_distinct_from() method of ColumnOperators

Implement the IS NOT DISTINCT FROM operator.

Renders “a IS NOT DISTINCT FROM b” on most platforms; on some such as SQLite may render “a IS b”.

Changed in version 1.4: The is_not_distinct_from() operator is renamed from isnot_distinct_from() in previous releases. The previous name remains available for backwards compatibility.

method sqlalchemy.orm.PropComparator.isnot(other: Any) → ColumnOperators¶

inherited from the ColumnOperators.isnot() method of ColumnOperators

Implement the IS NOT operator.

Normally, IS NOT is generated automatically when comparing to a value of None, which resolves to NULL. However, explicit usage of IS NOT may be desirable if comparing to boolean values on certain platforms.

Changed in version 1.4: The is_not() operator is renamed from isnot() in previous releases. The previous name remains available for backwards compatibility.

See also

ColumnOperators.is_()

method sqlalchemy.orm.PropComparator.isnot_distinct_from(other: Any) → ColumnOperators¶

inherited from the ColumnOperators.isnot_distinct_from() method of ColumnOperators

Implement the IS NOT DISTINCT FROM operator.

Renders “a IS NOT DISTINCT FROM b” on most platforms; on some such as SQLite may render “a IS b”.

Changed in version 1.4: The is_not_distinct_from() operator is renamed from isnot_distinct_from() in previous releases. The previous name remains available for backwards compatibility.

method sqlalchemy.orm.PropComparator.istartswith(other: Any, escape: str | None = None, autoescape: bool = False) → ColumnOperators¶

inherited from the ColumnOperators.istartswith() method of ColumnOperators

Implement the istartswith operator, e.g. case insensitive version of ColumnOperators.startswith().

Produces a LIKE expression that tests against an insensitive match for the start of a string value:

lower(column) LIKE lower(<other>) || '%'

E.g.:

stmt = select(sometable).\
    where(sometable.c.column.istartswith("foobar"))

Since the operator uses LIKE, wildcard characters "%" and "_" that are present inside the <other> expression will behave like wildcards as well. For literal string values, the ColumnOperators.istartswith.autoescape flag may be set to True to apply escaping to occurrences of these characters within the string value so that they match as themselves and not as wildcard characters. Alternatively, the ColumnOperators.istartswith.escape parameter will establish a given character as an escape character which can be of use when the target expression is not a literal string.

Parameters:

other¶ – expression to be compared. This is usually a plain string value, but can also be an arbitrary SQL expression. LIKE wildcard characters % and _ are not escaped by default unless the ColumnOperators.istartswith.autoescape flag is set to True.
autoescape¶ –
boolean; when True, establishes an escape character within the LIKE expression, then applies it to all occurrences of "%", "_" and the escape character itself within the comparison value, which is assumed to be a literal string and not a SQL expression.

An expression such as:
```
somecolumn.istartswith("foo%bar", autoescape=True)
```
Will render as:
```
lower(somecolumn) LIKE lower(:param) || '%' ESCAPE '/'
```
With the value of :param as "foo/%bar".
escape¶ –
a character which when given will render with the ESCAPE keyword to establish that character as the escape character. This character can then be placed preceding occurrences of % and _ to allow them to act as themselves and not wildcard characters.

An expression such as:
```
somecolumn.istartswith("foo/%bar", escape="^")
```
Will render as:
```
lower(somecolumn) LIKE lower(:param) || '%' ESCAPE '^'
```
The parameter may also be combined with ColumnOperators.istartswith.autoescape:
```
somecolumn.istartswith("foo%bar^bat", escape="^", autoescape=True)
```
Where above, the given literal parameter will be converted to "foo^%bar^^bat" before being passed to the database.

See also

ColumnOperators.startswith()

method sqlalchemy.orm.PropComparator.like(other: Any, escape: str | None = None) → ColumnOperators¶

inherited from the ColumnOperators.like() method of ColumnOperators

Implement the like operator.

In a column context, produces the expression:

a LIKE other

E.g.:

stmt = select(sometable).\
    where(sometable.c.column.like("%foobar%"))

Parameters:

other¶ – expression to be compared
escape¶ –
optional escape character, renders the ESCAPE keyword, e.g.:
```
somecolumn.like("foo/%bar", escape="/")
```

See also

ColumnOperators.ilike()

method sqlalchemy.orm.PropComparator.match(other: Any, **kwargs: Any) → ColumnOperators¶

inherited from the ColumnOperators.match() method of ColumnOperators

Implements a database-specific ‘match’ operator.

ColumnOperators.match() attempts to resolve to a MATCH-like function or operator provided by the backend. Examples include:

PostgreSQL - renders x @@ plainto_tsquery(y)

Changed in version 2.0: plainto_tsquery() is used instead of to_tsquery() for PostgreSQL now; for compatibility with other forms, see Full Text Search.
MySQL - renders MATCH (x) AGAINST (y IN BOOLEAN MODE)

See also

match - MySQL specific construct with additional features.
Oracle - renders CONTAINS(x, y)
other backends may provide special implementations.
Backends without any special implementation will emit the operator as “MATCH”. This is compatible with SQLite, for example.

method sqlalchemy.orm.PropComparator.not_ilike(other: Any, escape: str | None = None) → ColumnOperators¶

inherited from the ColumnOperators.not_ilike() method of ColumnOperators

implement the NOT ILIKE operator.

This is equivalent to using negation with ColumnOperators.ilike(), i.e. ~x.ilike(y).

Changed in version 1.4: The not_ilike() operator is renamed from notilike() in previous releases. The previous name remains available for backwards compatibility.

See also

ColumnOperators.ilike()

method sqlalchemy.orm.PropComparator.not_in(other: Any) → ColumnOperators¶

inherited from the ColumnOperators.not_in() method of ColumnOperators

implement the NOT IN operator.

This is equivalent to using negation with ColumnOperators.in_(), i.e. ~x.in_(y).

In the case that other is an empty sequence, the compiler produces an “empty not in” expression. This defaults to the expression “1 = 1” to produce true in all cases. The create_engine.empty_in_strategy may be used to alter this behavior.

Changed in version 1.4: The not_in() operator is renamed from notin_() in previous releases. The previous name remains available for backwards compatibility.

Changed in version 1.2: The ColumnOperators.in_() and ColumnOperators.not_in() operators now produce a “static” expression for an empty IN sequence by default.

See also

ColumnOperators.in_()

method sqlalchemy.orm.PropComparator.not_like(other: Any, escape: str | None = None) → ColumnOperators¶

inherited from the ColumnOperators.not_like() method of ColumnOperators

implement the NOT LIKE operator.

This is equivalent to using negation with ColumnOperators.like(), i.e. ~x.like(y).

Changed in version 1.4: The not_like() operator is renamed from notlike() in previous releases. The previous name remains available for backwards compatibility.

See also

ColumnOperators.ilike()

method sqlalchemy.orm.PropComparator.notilike(other: Any, escape: str | None = None) → ColumnOperators¶

inherited from the ColumnOperators.notilike() method of ColumnOperators

implement the NOT ILIKE operator.

This is equivalent to using negation with ColumnOperators.ilike(), i.e. ~x.ilike(y).

Changed in version 1.4: The not_ilike() operator is renamed from notilike() in previous releases. The previous name remains available for backwards compatibility.

See also

method sqlalchemy.orm.PropComparator.notin_(other: Any) → ColumnOperators¶

inherited from the ColumnOperators.notin_() method of ColumnOperators

implement the NOT IN operator.

This is equivalent to using negation with ColumnOperators.in_(), i.e. ~x.in_(y).

In the case that other is an empty sequence, the compiler produces an “empty not in” expression. This defaults to the expression “1 = 1” to produce true in all cases. The create_engine.empty_in_strategy may be used to alter this behavior.

Changed in version 1.4: The not_in() operator is renamed from notin_() in previous releases. The previous name remains available for backwards compatibility.

Changed in version 1.2: The ColumnOperators.in_() and ColumnOperators.not_in() operators now produce a “static” expression for an empty IN sequence by default.

See also

ColumnOperators.in_()

method sqlalchemy.orm.PropComparator.notlike(other: Any, escape: str | None = None) → ColumnOperators¶

inherited from the ColumnOperators.notlike() method of ColumnOperators

implement the NOT LIKE operator.

This is equivalent to using negation with ColumnOperators.like(), i.e. ~x.like(y).

Changed in version 1.4: The not_like() operator is renamed from notlike() in previous releases. The previous name remains available for backwards compatibility.

See also

Joining to specific sub-types or with_polymorphic() entities

method sqlalchemy.orm.PropComparator.nulls_first() → ColumnOperators¶: inherited from the ColumnOperators.nulls_first() method of ColumnOperators

Produce a nulls_first() clause against the parent object.

Changed in version 1.4: The nulls_first() operator is renamed from nullsfirst() in previous releases. The previous name remains available for backwards compatibility.

method sqlalchemy.orm.PropComparator.nulls_last() → ColumnOperators¶: inherited from the ColumnOperators.nulls_last() method of ColumnOperators

Produce a nulls_last() clause against the parent object.

Changed in version 1.4: The nulls_last() operator is renamed from nullslast() in previous releases. The previous name remains available for backwards compatibility.

method sqlalchemy.orm.PropComparator.nullsfirst() → ColumnOperators¶: inherited from the ColumnOperators.nullsfirst() method of ColumnOperators

Produce a nulls_first() clause against the parent object.

Changed in version 1.4: The nulls_first() operator is renamed from nullsfirst() in previous releases. The previous name remains available for backwards compatibility.

method sqlalchemy.orm.PropComparator.nullslast() → ColumnOperators¶: inherited from the ColumnOperators.nullslast() method of ColumnOperators

Produce a nulls_last() clause against the parent object.

Changed in version 1.4: The nulls_last() operator is renamed from nullslast() in previous releases. The previous name remains available for backwards compatibility.

method sqlalchemy.orm.PropComparator.of_type(class_: _EntityType[Any]) → PropComparator[_T_co]¶

Redefine this object in terms of a polymorphic subclass, with_polymorphic() construct, or aliased() construct.

Returns a new PropComparator from which further criterion can be evaluated.

e.g.:

query.join(Company.employees.of_type(Engineer)).\
   filter(Engineer.name=='foo')

Parameters:: class_¶ – a class or mapper indicating that criterion will be against this specific subclass.

method sqlalchemy.orm.PropComparator.op(opstring: str, precedence: int = 0, is_comparison: bool = False, return_type: Type[TypeEngine[Any]] | TypeEngine[Any] | None = None, python_impl: Callable[..., Any] | None = None) → Callable[[Any], Operators]¶

inherited from the Operators.op() method of Operators

Produce a generic operator function.

e.g.:

somecolumn.op("*")(5)

produces:

somecolumn * 5

This function can also be used to make bitwise operators explicit. For example:

somecolumn.op('&')(0xff)

is a bitwise AND of the value in somecolumn.

Parameters:

opstring¶ – a string which will be output as the infix operator between this element and the expression passed to the generated function.
precedence¶ –
precedence which the database is expected to apply to the operator in SQL expressions. This integer value acts as a hint for the SQL compiler to know when explicit parenthesis should be rendered around a particular operation. A lower number will cause the expression to be parenthesized when applied against another operator with higher precedence. The default value of 0 is lower than all operators except for the comma (,) and AS operators. A value of 100 will be higher or equal to all operators, and -100 will be lower than or equal to all operators.

See also

I’m using op() to generate a custom operator and my parenthesis are not coming out correctly - detailed description of how the SQLAlchemy SQL compiler renders parenthesis
is_comparison¶ –
legacy; if True, the operator will be considered as a “comparison” operator, that is which evaluates to a boolean true/false value, like ==, >, etc. This flag is provided so that ORM relationships can establish that the operator is a comparison operator when used in a custom join condition.

Using the is_comparison parameter is superseded by using the Operators.bool_op() method instead; this more succinct operator sets this parameter automatically, but also provides correct PEP 484 typing support as the returned object will express a “boolean” datatype, i.e. BinaryExpression[bool].
return_type¶ – a TypeEngine class or object that will force the return type of an expression produced by this operator to be of that type. By default, operators that specify Operators.op.is_comparison will resolve to Boolean, and those that do not will be of the same type as the left-hand operand.
python_impl¶ –
an optional Python function that can evaluate two Python values in the same way as this operator works when run on the database server. Useful for in-Python SQL expression evaluation functions, such as for ORM hybrid attributes, and the ORM “evaluator” used to match objects in a session after a multi-row update or delete.

e.g.:
```
>>> expr = column('x').op('+', python_impl=lambda a, b: a + b)('y')
```
The operator for the above expression will also work for non-SQL left and right objects:
```
>>> expr.operator(5, 10)
15
```
New in version 2.0.

See also

Operators.bool_op()

Using custom operators in join conditions

method sqlalchemy.orm.PropComparator.operate(op: OperatorType, *other: Any, **kwargs: Any) → Operators¶

inherited from the Operators.operate() method of Operators

Operate on an argument.

This is the lowest level of operation, raises NotImplementedError by default.

Overriding this on a subclass can allow common behavior to be applied to all operations. For example, overriding ColumnOperators to apply func.lower() to the left and right side:

class MyComparator(ColumnOperators):
    def operate(self, op, other, **kwargs):
        return op(func.lower(self), func.lower(other), **kwargs)

Parameters:

op¶ – Operator callable.
*other¶ – the ‘other’ side of the operation. Will be a single scalar for most operations.
**kwargs¶ – modifiers. These may be passed by special operators such as ColumnOperators.contains().

attribute sqlalchemy.orm.PropComparator.property¶

Return the MapperProperty associated with this PropComparator.

Return values here will commonly be instances of ColumnProperty or Relationship.

method sqlalchemy.orm.PropComparator.regexp_match(pattern: Any, flags: str | None = None) → ColumnOperators¶

inherited from the ColumnOperators.regexp_match() method of ColumnOperators

Implements a database-specific ‘regexp match’ operator.

E.g.:

stmt = select(table.c.some_column).where(
    table.c.some_column.regexp_match('^(b|c)')
)

ColumnOperators.regexp_match() attempts to resolve to a REGEXP-like function or operator provided by the backend, however the specific regular expression syntax and flags available are not backend agnostic.

Examples include:

PostgreSQL - renders x ~ y or x !~ y when negated.
Oracle - renders REGEXP_LIKE(x, y)
SQLite - uses SQLite’s REGEXP placeholder operator and calls into the Python re.match() builtin.
other backends may provide special implementations.
Backends without any special implementation will emit the operator as “REGEXP” or “NOT REGEXP”. This is compatible with SQLite and MySQL, for example.

Regular expression support is currently implemented for Oracle, PostgreSQL, MySQL and MariaDB. Partial support is available for SQLite. Support among third-party dialects may vary.

Parameters:

pattern¶ – The regular expression pattern string or column clause.
flags¶ – Any regular expression string flags to apply, passed as plain Python string only. These flags are backend specific. Some backends, like PostgreSQL and MariaDB, may alternatively specify the flags as part of the pattern. When using the ignore case flag ‘i’ in PostgreSQL, the ignore case regexp match operator ~* or !~* will be used.

New in version 1.4.

Changed in version 1.4.48,: 2.0.18 Note that due to an implementation error, the “flags” parameter previously accepted SQL expression objects such as column expressions in addition to plain Python strings. This implementation did not work correctly with caching and was removed; strings only should be passed for the “flags” parameter, as these flags are rendered as literal inline values within SQL expressions.

See also

ColumnOperators.regexp_replace()

method sqlalchemy.orm.PropComparator.regexp_replace(pattern: Any, replacement: Any, flags: str | None = None) → ColumnOperators¶

inherited from the ColumnOperators.regexp_replace() method of ColumnOperators

Implements a database-specific ‘regexp replace’ operator.

E.g.:

stmt = select(
    table.c.some_column.regexp_replace(
        'b(..)',
        'XY',
        flags='g'
    )
)

ColumnOperators.regexp_replace() attempts to resolve to a REGEXP_REPLACE-like function provided by the backend, that usually emit the function REGEXP_REPLACE(). However, the specific regular expression syntax and flags available are not backend agnostic.

Regular expression replacement support is currently implemented for Oracle, PostgreSQL, MySQL 8 or greater and MariaDB. Support among third-party dialects may vary.

Parameters:

pattern¶ – The regular expression pattern string or column clause.
pattern¶ – The replacement string or column clause.
flags¶ – Any regular expression string flags to apply, passed as plain Python string only. These flags are backend specific. Some backends, like PostgreSQL and MariaDB, may alternatively specify the flags as part of the pattern.

New in version 1.4.

Changed in version 1.4.48,: 2.0.18 Note that due to an implementation error, the “flags” parameter previously accepted SQL expression objects such as column expressions in addition to plain Python strings. This implementation did not work correctly with caching and was removed; strings only should be passed for the “flags” parameter, as these flags are rendered as literal inline values within SQL expressions.

See also

ColumnOperators.regexp_match()

method sqlalchemy.orm.PropComparator.reverse_operate(op: OperatorType, other: Any, **kwargs: Any) → Operators¶

inherited from the Operators.reverse_operate() method of Operators

Reverse operate on an argument.

Usage is the same as operate().

method sqlalchemy.orm.PropComparator.startswith(other: Any, escape: str | None = None, autoescape: bool = False) → ColumnOperators¶

inherited from the ColumnOperators.startswith() method of ColumnOperators

Implement the startswith operator.

Produces a LIKE expression that tests against a match for the start of a string value:

column LIKE <other> || '%'

E.g.:

stmt = select(sometable).\
    where(sometable.c.column.startswith("foobar"))

Since the operator uses LIKE, wildcard characters "%" and "_" that are present inside the <other> expression will behave like wildcards as well. For literal string values, the ColumnOperators.startswith.autoescape flag may be set to True to apply escaping to occurrences of these characters within the string value so that they match as themselves and not as wildcard characters. Alternatively, the ColumnOperators.startswith.escape parameter will establish a given character as an escape character which can be of use when the target expression is not a literal string.

Parameters:

other¶ – expression to be compared. This is usually a plain string value, but can also be an arbitrary SQL expression. LIKE wildcard characters % and _ are not escaped by default unless the ColumnOperators.startswith.autoescape flag is set to True.
autoescape¶ –
boolean; when True, establishes an escape character within the LIKE expression, then applies it to all occurrences of "%", "_" and the escape character itself within the comparison value, which is assumed to be a literal string and not a SQL expression.

An expression such as:
```
somecolumn.startswith("foo%bar", autoescape=True)
```
Will render as:
```
somecolumn LIKE :param || '%' ESCAPE '/'
```
With the value of :param as "foo/%bar".
escape¶ –
a character which when given will render with the ESCAPE keyword to establish that character as the escape character. This character can then be placed preceding occurrences of % and _ to allow them to act as themselves and not wildcard characters.

An expression such as:
```
somecolumn.startswith("foo/%bar", escape="^")
```
Will render as:
```
somecolumn LIKE :param || '%' ESCAPE '^'
```
The parameter may also be combined with ColumnOperators.startswith.autoescape:
```
somecolumn.startswith("foo%bar^bat", escape="^", autoescape=True)
```
Where above, the given literal parameter will be converted to "foo^%bar^^bat" before being passed to the database.

See also

ColumnOperators.endswith()

ColumnOperators.contains()

Relationship Configuration

attribute sqlalchemy.orm.PropComparator.timetuple: Literal[None] = None¶: inherited from the ColumnOperators.timetuple attribute of ColumnOperators

Hack, allows datetime objects to be compared on the LHS.

class sqlalchemy.orm.Relationship¶

Describes an object property that holds a single item or list of items that correspond to a related database table.

Public constructor is the relationship() function.

See also

Changed in version 2.0: Added Relationship as a Declarative compatible subclass for RelationshipProperty.

Class signature

class sqlalchemy.orm.Relationship (sqlalchemy.orm.RelationshipProperty, sqlalchemy.orm.base._DeclarativeMapped)

class sqlalchemy.orm.RelationshipDirection¶

enumeration which indicates the ‘direction’ of a RelationshipProperty.

RelationshipDirection is accessible from the Relationship.direction attribute of RelationshipProperty.

Members

MANYTOMANY, MANYTOONE, ONETOMANY

Class signature

class sqlalchemy.orm.RelationshipDirection (enum.Enum)

attribute sqlalchemy.orm.RelationshipDirection.MANYTOMANY = 3¶

Indicates the many-to-many direction for a relationship().

This symbol is typically used by the internals but may be exposed within certain API features.

attribute sqlalchemy.orm.RelationshipDirection.MANYTOONE = 2¶

Indicates the many-to-one direction for a relationship().

This symbol is typically used by the internals but may be exposed within certain API features.

attribute sqlalchemy.orm.RelationshipDirection.ONETOMANY = 1¶

Indicates the one-to-many direction for a relationship().

This symbol is typically used by the internals but may be exposed within certain API features.

class sqlalchemy.orm.RelationshipProperty¶

Describes an object property that holds a single item or list of items that correspond to a related database table.

Public constructor is the relationship() function.

See also

Relationship Configuration

Members

__eq__(), __init__(), __ne__(), adapt_to_entity(), and_(), any(), contains(), entity, has(), in_(), mapper, of_type(), cascade, cascade_iterator(), declarative_scan(), do_init(), entity, instrument_class(), mapper, merge()

Class signature

class sqlalchemy.orm.RelationshipProperty (sqlalchemy.orm._IntrospectsAnnotations, sqlalchemy.orm.StrategizedProperty, sqlalchemy.log.Identified)

class Comparator¶

Produce boolean, comparison, and other operators for RelationshipProperty attributes.

See the documentation for PropComparator for a brief overview of ORM level operator definition.

See also

PropComparator

Comparator

QueryableAttribute.info

Class signature

class sqlalchemy.orm.RelationshipProperty.Comparator (sqlalchemy.util.langhelpers.MemoizedSlots, sqlalchemy.orm.PropComparator)

method sqlalchemy.orm.RelationshipProperty.Comparator.__eq__(other: Any) → ColumnElement[bool]¶

Implement the == operator.

In a many-to-one context, such as:

MyClass.some_prop == <some object>

this will typically produce a clause such as:

mytable.related_id == <some id>

Where <some id> is the primary key of the given object.

The == operator provides partial functionality for non- many-to-one comparisons:

Comparisons against collections are not supported. Use Comparator.contains().
Compared to a scalar one-to-many, will produce a clause that compares the target columns in the parent to the given target.
Compared to a scalar many-to-many, an alias of the association table will be rendered as well, forming a natural join that is part of the main body of the query. This will not work for queries that go beyond simple AND conjunctions of comparisons, such as those which use OR. Use explicit joins, outerjoins, or Comparator.has() for more comprehensive non-many-to-one scalar membership tests.
Comparisons against None given in a one-to-many or many-to-many context produce a NOT EXISTS clause.

method sqlalchemy.orm.RelationshipProperty.Comparator.__init__(prop: RelationshipProperty[_PT], parentmapper: _InternalEntityType[Any], adapt_to_entity: AliasedInsp[Any] | None = None, of_type: _EntityType[_PT] | None = None, extra_criteria: Tuple[ColumnElement[bool], ...] = ())¶: Construction of Comparator is internal to the ORM’s attribute mechanics.

method sqlalchemy.orm.RelationshipProperty.Comparator.__ne__(other: Any) → ColumnElement[bool]¶

Implement the != operator.

In a many-to-one context, such as:

MyClass.some_prop != <some object>

This will typically produce a clause such as:

mytable.related_id != <some id>

Where <some id> is the primary key of the given object.

The != operator provides partial functionality for non- many-to-one comparisons:

Comparisons against collections are not supported. Use Comparator.contains() in conjunction with not_().
Compared to a scalar one-to-many, will produce a clause that compares the target columns in the parent to the given target.
Compared to a scalar many-to-many, an alias of the association table will be rendered as well, forming a natural join that is part of the main body of the query. This will not work for queries that go beyond simple AND conjunctions of comparisons, such as those which use OR. Use explicit joins, outerjoins, or Comparator.has() in conjunction with not_() for more comprehensive non-many-to-one scalar membership tests.
Comparisons against None given in a one-to-many or many-to-many context produce an EXISTS clause.

method sqlalchemy.orm.RelationshipProperty.Comparator.adapt_to_entity(adapt_to_entity: AliasedInsp[Any]) → RelationshipProperty.Comparator[Any]¶: Return a copy of this PropComparator which will use the given AliasedInsp to produce corresponding expressions.

method sqlalchemy.orm.RelationshipProperty.Comparator.and_(*criteria: _ColumnExpressionArgument[bool]) → PropComparator[Any]¶

Add AND criteria.

See PropComparator.and_() for an example.

New in version 1.4.

method sqlalchemy.orm.RelationshipProperty.Comparator.any(criterion: _ColumnExpressionArgument[bool] | None = None, **kwargs: Any) → ColumnElement[bool]¶

Produce an expression that tests a collection against particular criterion, using EXISTS.

An expression like:

session.query(MyClass).filter(
    MyClass.somereference.any(SomeRelated.x==2)
)

Will produce a query like:

SELECT * FROM my_table WHERE
EXISTS (SELECT 1 FROM related WHERE related.my_id=my_table.id
AND related.x=2)

Because Comparator.any() uses a correlated subquery, its performance is not nearly as good when compared against large target tables as that of using a join.

Comparator.any() is particularly useful for testing for empty collections:

session.query(MyClass).filter(
    ~MyClass.somereference.any()
)

will produce:

SELECT * FROM my_table WHERE
NOT (EXISTS (SELECT 1 FROM related WHERE
related.my_id=my_table.id))

Comparator.any() is only valid for collections, i.e. a relationship() that has uselist=True. For scalar references, use Comparator.has().

method sqlalchemy.orm.RelationshipProperty.Comparator.contains(other: _ColumnExpressionArgument[Any], **kwargs: Any) → ColumnElement[bool]¶

Return a simple expression that tests a collection for containment of a particular item.

Comparator.contains() is only valid for a collection, i.e. a relationship() that implements one-to-many or many-to-many with uselist=True.

When used in a simple one-to-many context, an expression like:

MyClass.contains(other)

Produces a clause like:

mytable.id == <some id>

Where <some id> is the value of the foreign key attribute on other which refers to the primary key of its parent object. From this it follows that Comparator.contains() is very useful when used with simple one-to-many operations.

For many-to-many operations, the behavior of Comparator.contains() has more caveats. The association table will be rendered in the statement, producing an “implicit” join, that is, includes multiple tables in the FROM clause which are equated in the WHERE clause:

query(MyClass).filter(MyClass.contains(other))

Produces a query like:

SELECT * FROM my_table, my_association_table AS
my_association_table_1 WHERE
my_table.id = my_association_table_1.parent_id
AND my_association_table_1.child_id = <some id>

Where <some id> would be the primary key of other. From the above, it is clear that Comparator.contains() will not work with many-to-many collections when used in queries that move beyond simple AND conjunctions, such as multiple Comparator.contains() expressions joined by OR. In such cases subqueries or explicit “outer joins” will need to be used instead. See Comparator.any() for a less-performant alternative using EXISTS, or refer to Query.outerjoin() as well as Joins for more details on constructing outer joins.

kwargs may be ignored by this operator but are required for API conformance.

attribute sqlalchemy.orm.RelationshipProperty.Comparator.entity: _InternalEntityType[_PT]¶

The target entity referred to by this Comparator.

This is either a Mapper or AliasedInsp object.

This is the “target” or “remote” side of the relationship().

method sqlalchemy.orm.RelationshipProperty.Comparator.has(criterion: _ColumnExpressionArgument[bool] | None = None, **kwargs: Any) → ColumnElement[bool]¶

Produce an expression that tests a scalar reference against particular criterion, using EXISTS.

An expression like:

session.query(MyClass).filter(
    MyClass.somereference.has(SomeRelated.x==2)
)

Will produce a query like:

SELECT * FROM my_table WHERE
EXISTS (SELECT 1 FROM related WHERE
related.id==my_table.related_id AND related.x=2)

Because Comparator.has() uses a correlated subquery, its performance is not nearly as good when compared against large target tables as that of using a join.

Comparator.has() is only valid for scalar references, i.e. a relationship() that has uselist=False. For collection references, use Comparator.any().

method sqlalchemy.orm.RelationshipProperty.Comparator.in_(other: Any) → NoReturn¶: Produce an IN clause - this is not implemented for relationship()-based attributes at this time.

attribute sqlalchemy.orm.RelationshipProperty.Comparator.mapper: Mapper[_PT]¶

The target Mapper referred to by this Comparator.

This is the “target” or “remote” side of the relationship().

method sqlalchemy.orm.RelationshipProperty.Comparator.of_type(class_: _EntityType[Any]) → PropComparator[_PT]¶

Redefine this object in terms of a polymorphic subclass.

See PropComparator.of_type() for an example.

attribute sqlalchemy.orm.RelationshipProperty.cascade¶: Return the current cascade setting for this RelationshipProperty.

method sqlalchemy.orm.RelationshipProperty.cascade_iterator(type_: str, state: InstanceState[Any], dict_: _InstanceDict, visited_states: Set[InstanceState[Any]], halt_on: Callable[[InstanceState[Any]], bool] | None = None) → Iterator[Tuple[Any, Mapper[Any], InstanceState[Any], _InstanceDict]]¶

Iterate through instances related to the given instance for a particular ‘cascade’, starting with this MapperProperty.

Return an iterator3-tuples (instance, mapper, state).

Note that the ‘cascade’ collection on this MapperProperty is checked first for the given type before cascade_iterator is called.

This method typically only applies to Relationship.

method sqlalchemy.orm.RelationshipProperty.declarative_scan(decl_scan: _ClassScanMapperConfig, registry: _RegistryType, cls: Type[Any], originating_module: str | None, key: str, mapped_container: Type[Mapped[Any]] | None, annotation: _AnnotationScanType | None, extracted_mapped_annotation: _AnnotationScanType | None, is_dataclass_field: bool) → None¶: Perform class-specific initializaton at early declarative scanning time.

New in version 2.0.

method sqlalchemy.orm.RelationshipProperty.do_init() → None¶

Perform subclass-specific initialization post-mapper-creation steps.

This is a template method called by the MapperProperty object’s init() method.

attribute sqlalchemy.orm.RelationshipProperty.entity¶: Return the target mapped entity, which is an inspect() of the class or aliased class that is referenced by this RelationshipProperty.

method sqlalchemy.orm.RelationshipProperty.instrument_class(mapper: Mapper[Any]) → None¶

Hook called by the Mapper to the property to initiate instrumentation of the class attribute managed by this MapperProperty.

The MapperProperty here will typically call out to the attributes module to set up an InstrumentedAttribute.

This step is the first of two steps to set up an InstrumentedAttribute, and is called early in the mapper setup process.

The second step is typically the init_class_attribute step, called from StrategizedProperty via the post_instrument_class() hook. This step assigns additional state to the InstrumentedAttribute (specifically the “impl”) which has been determined after the MapperProperty has determined what kind of persistence management it needs to do (e.g. scalar, object, collection, etc).

attribute sqlalchemy.orm.RelationshipProperty.mapper¶: Return the targeted Mapper for this RelationshipProperty.

method sqlalchemy.orm.RelationshipProperty.merge(session: Session, source_state: InstanceState[Any], source_dict: _InstanceDict, dest_state: InstanceState[Any], dest_dict: _InstanceDict, load: bool, _recursive: Dict[Any, object], _resolve_conflict_map: Dict[_IdentityKeyType[Any], object]) → None¶: Merge the attribute represented by this MapperProperty from source to destination object.

class sqlalchemy.orm.SQLORMExpression¶

A type that may be used to indicate any ORM-level attribute or object that acts in place of one, in the context of SQL expression construction.

SQLORMExpression extends from the Core SQLColumnExpression to add additional SQL methods that are ORM specific, such as PropComparator.of_type(), and is part of the bases for InstrumentedAttribute. It may be used in PEP 484 typing to indicate arguments or return values that should behave as ORM-level attribute expressions.

New in version 2.0.0b4.

Class signature

class sqlalchemy.orm.SQLORMExpression (sqlalchemy.orm.base.SQLORMOperations, sqlalchemy.sql.expression.SQLColumnExpression, sqlalchemy.util.langhelpers.TypingOnly)

class sqlalchemy.orm.Synonym¶

Declarative front-end for the SynonymProperty class.

Public constructor is the synonym() function.

Changed in version 2.0: Added Synonym as a Declarative compatible subclass for SynonymProperty

See also

Synonyms - Overview of synonyms

Class signature

class sqlalchemy.orm.Synonym (sqlalchemy.orm.descriptor_props.SynonymProperty, sqlalchemy.orm.base._DeclarativeMapped)

class sqlalchemy.orm.SynonymProperty¶

Denote an attribute name as a synonym to a mapped property, in that the attribute will mirror the value and expression behavior of another attribute.

Synonym is constructed using the synonym() function.

See also

Synonyms - Overview of synonyms

Members

doc, info, key, parent, set_parent(), uses_objects

Class signature

class sqlalchemy.orm.SynonymProperty (sqlalchemy.orm.descriptor_props.DescriptorProperty)

attribute sqlalchemy.orm.SynonymProperty.doc: str | None¶: inherited from the DescriptorProperty.doc attribute of DescriptorProperty

optional documentation string

attribute sqlalchemy.orm.SynonymProperty.info: _InfoType¶

inherited from the MapperProperty.info attribute of MapperProperty

Info dictionary associated with the object, allowing user-defined data to be associated with this InspectionAttr.

The dictionary is generated when first accessed. Alternatively, it can be specified as a constructor argument to the column_property(), relationship(), or composite() functions.

See also

Mapper.all_orm_descriptors

attribute sqlalchemy.orm.SynonymProperty.key: str¶: inherited from the MapperProperty.key attribute of MapperProperty

name of class attribute

attribute sqlalchemy.orm.SynonymProperty.parent: Mapper[Any]¶: inherited from the MapperProperty.parent attribute of MapperProperty

the Mapper managing this property.

method sqlalchemy.orm.SynonymProperty.set_parent(parent: Mapper[Any], init: bool) → None¶

Set the parent mapper that references this MapperProperty.

This method is overridden by some subclasses to perform extra setup when the mapper is first known.

attribute sqlalchemy.orm.SynonymProperty.uses_objects¶

class sqlalchemy.orm.QueryContext¶

class default_load_options¶: Class signature

class sqlalchemy.orm.QueryContext.default_load_options (sqlalchemy.sql.expression.Options)

class sqlalchemy.orm.QueryableAttribute¶

Base class for descriptor objects that intercept attribute events on behalf of a MapperProperty object. The actual MapperProperty is accessible via the QueryableAttribute.property attribute.

See also

InstrumentedAttribute

MapperProperty

Mapper.attrs

Members

adapt_to_entity(), and_(), expression, info, is_attribute, of_type(), operate(), parent, reverse_operate()

Class signature

class sqlalchemy.orm.QueryableAttribute (sqlalchemy.orm.base._DeclarativeMapped, sqlalchemy.orm.base.SQLORMExpression, sqlalchemy.orm.base.InspectionAttr, sqlalchemy.orm.PropComparator, sqlalchemy.sql.roles.JoinTargetRole, sqlalchemy.sql.roles.OnClauseRole, sqlalchemy.sql.expression.Immutable, sqlalchemy.sql.cache_key.SlotsMemoizedHasCacheKey, sqlalchemy.util.langhelpers.MemoizedSlots, sqlalchemy.event.registry.EventTarget)

method sqlalchemy.orm.QueryableAttribute.adapt_to_entity(adapt_to_entity: AliasedInsp[Any]) → Self¶: Return a copy of this PropComparator which will use the given AliasedInsp to produce corresponding expressions.

method sqlalchemy.orm.QueryableAttribute.and_(*clauses: _ColumnExpressionArgument[bool]) → QueryableAttribute[bool]¶

Add additional criteria to the ON clause that’s represented by this relationship attribute.

E.g.:

stmt = select(User).join(
    User.addresses.and_(Address.email_address != 'foo')
)

stmt = select(User).options(
    joinedload(User.addresses.and_(Address.email_address != 'foo'))
)

New in version 1.4.

Adding Criteria to loader options

with_loader_criteria()

attribute sqlalchemy.orm.QueryableAttribute.expression: ColumnElement[_T_co]¶

The SQL expression object represented by this QueryableAttribute.

This will typically be an instance of a ColumnElement subclass representing a column expression.

attribute sqlalchemy.orm.QueryableAttribute.info¶

Return the ‘info’ dictionary for the underlying SQL element.

The behavior here is as follows:

If the attribute is a column-mapped property, i.e. ColumnProperty, which is mapped directly to a schema-level Column object, this attribute will return the SchemaItem.info dictionary associated with the core-level Column object.
If the attribute is a ColumnProperty but is mapped to any other kind of SQL expression other than a Column, the attribute will refer to the MapperProperty.info dictionary associated directly with the ColumnProperty, assuming the SQL expression itself does not have its own .info attribute (which should be the case, unless a user-defined SQL construct has defined one).
If the attribute refers to any other kind of MapperProperty, including Relationship, the attribute will refer to the MapperProperty.info dictionary associated with that MapperProperty.
To access the MapperProperty.info dictionary of the MapperProperty unconditionally, including for a ColumnProperty that’s associated directly with a Column, the attribute can be referred to using QueryableAttribute.property attribute, as MyClass.someattribute.property.info.

See also