sqlalchemy.orm.interfaces.MapperProperty

class documentation

class MapperProperty(HasCacheKey, _MappedAttribute, InspectionAttr, util.MemoizedSlots):

Known subclasses: sqlalchemy.orm.descriptor_props.DescriptorProperty, sqlalchemy.orm.interfaces.StrategizedProperty

Represent a particular class attribute mapped by _orm.Mapper.

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

Method	`__init__`	Undocumented
Method	`__repr__`	Undocumented
Method	`_memoized_attr_info`	Info dictionary associated with the object, allowing user-defined data to be associated with this `.InspectionAttr`.
Method	`cascade_iterator`	Iterate through instances related to the given instance for a particular 'cascade', starting with this MapperProperty.
Method	`create_row_processor`	Produce row processing functions and append to the given set of populators lists.
Method	`do_init`	Perform subclass-specific initialization post-mapper-creation steps.
Method	`init`	Called after all mappers are created to assemble relationships between mappers and perform other post-mapper-creation initialization steps.
Method	`instrument_class`	Hook called by the Mapper to the property to initiate instrumentation of the class attribute managed by this MapperProperty.
Method	`merge`	Merge the attribute represented by this `MapperProperty` from source to destination object.
Method	`post_instrument_class`	Perform instrumentation adjustments that need to occur after init() has completed.
Method	`set_parent`	Set the parent mapper that references this MapperProperty.
Method	`setup`	Called by Query for the purposes of constructing a SQL statement.
Class Variable	`__slots__`	Undocumented
Class Variable	`_cache_key_traversal`	Undocumented
Class Variable	`cascade`	The set of 'cascade' attribute names.
Class Variable	`is_property`	Part of the InspectionAttr interface; states this object is a mapper property.
Instance Variable	`_configure_finished`	Undocumented
Instance Variable	`_configure_started`	Undocumented
Instance Variable	`parent`	Undocumented
Property	`_links_to_entity`	True if this MapperProperty refers to a mapped entity.
Property	`class_attribute`	Return the class-bound descriptor corresponding to this `.MapperProperty`.

Inherited from HasCacheKey:

Class Variable	`inherit_cache`	Indicate if this `.HasCacheKey` instance should make use of the cache key generation scheme used by its immediate superclass.
Class Method	`_generate_cache_attrs`	generate cache key dispatcher for a new class.
Class Method	`_generate_cache_key_for_object`	Undocumented
Method	`_gen_cache_key`	return an optional cache key.
Method	`_generate_cache_key`	return a cache key.
Class Variable	`_hierarchy_supports_caching`	private attribute which may be set to False to prevent the inherit_cache warning from being emitted for a hierarchy of subclasses.
Class Variable	`_is_has_cache_key`	Undocumented

Inherited from InspectionAttr:

Class Variable	`_is_internal_proxy`	True if this object is an internal proxy object.
Class Variable	`is_aliased_class`	True if this object is an instance of `.AliasedClass`.
Class Variable	`is_attribute`	True if this object is a Python :term:`descriptor`.
Class Variable	`is_bundle`	True if this object is an instance of `.Bundle`.
Class Variable	`is_clause_element`	True if this object is an instance of `_expression.ClauseElement`.
Class Variable	`is_instance`	True if this object is an instance of `.InstanceState`.
Class Variable	`is_mapper`	True if this object is an instance of `_orm.Mapper`.
Class Variable	`is_selectable`	Return True if this object is an instance of `_expression.Selectable`.

Inherited from MemoizedSlots:

Method	`__getattr__`	Undocumented
Method	`_fallback_getattr`	Undocumented

def __init__(self):

overridden in sqlalchemy.orm.properties.ColumnProperty, sqlalchemy.orm.properties.CompositeProperty, sqlalchemy.orm.properties.ConcreteInheritedProperty, sqlalchemy.orm.properties.RelationshipProperty, sqlalchemy.orm.properties.SynonymProperty

Undocumented

def __repr__(self):

Undocumented

def _memoized_attr_info(self):

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, _orm.relationship, or .composite functions.

Changed in version 1.0.0: .MapperProperty.info is also available on extension types via the .InspectionAttrInfo.info attribute, so that it can apply to a wider variety of ORM and extension constructs.

See Also

.QueryableAttribute.info

.SchemaItem.info

def cascade_iterator(self, type_, state, dict_, visited_states, halt_on=None):

overridden in sqlalchemy.orm.properties.RelationshipProperty

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

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

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

This method typically only applies to RelationshipProperty.

def create_row_processor(self, context, query_entity, path, mapper, result, adapter, populators):

overridden in sqlalchemy.orm.interfaces.StrategizedProperty

Produce row processing functions and append to the given set of populators lists.

def do_init(self):

overridden in sqlalchemy.orm.interfaces.StrategizedProperty, sqlalchemy.orm.properties.CompositeProperty

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

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

def init(self):

Called after all mappers are created to assemble relationships between mappers and perform other post-mapper-creation initialization steps.

def instrument_class(self, mapper):

overridden in sqlalchemy.orm.properties.ColumnProperty, sqlalchemy.orm.descriptor_props.DescriptorProperty, sqlalchemy.orm.properties.RelationshipProperty

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

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

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

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

def merge(self, session, source_state, source_dict, dest_state, dest_dict, load, _recursive, _resolve_conflict_map):

overridden in sqlalchemy.orm.properties.ColumnProperty, sqlalchemy.orm.properties.RelationshipProperty

Merge the attribute represented by this MapperProperty from source to destination object.

def post_instrument_class(self, mapper):

overridden in sqlalchemy.orm.interfaces.StrategizedProperty

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

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

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

def set_parent(self, parent, init):

overridden in sqlalchemy.orm.properties.SynonymProperty

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.

def setup(self, context, query_entity, path, adapter, **kwargs):

overridden in sqlalchemy.orm.interfaces.StrategizedProperty

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.

__slots__: tuple[str, ...] =

overrides sqlalchemy.sql.traversals.HasCacheKey.__slots__

overridden in sqlalchemy.orm.interfaces.StrategizedProperty

Undocumented

_cache_key_traversal =

Undocumented

cascade =

overridden in sqlalchemy.orm.properties.RelationshipProperty

The set of 'cascade' attribute names.

This collection is checked before the 'cascade_iterator' method is called.

The collection typically only applies to a RelationshipProperty.

is_property: bool =

overrides sqlalchemy.orm.base.InspectionAttr.is_property

Part of the InspectionAttr interface; states this object is a mapper property.

_configure_finished: bool =

Undocumented

_configure_started: bool =

Undocumented

parent =

overridden in sqlalchemy.orm.properties.SynonymProperty

Undocumented

@property
_links_to_entity =

overridden in sqlalchemy.orm.properties.ColumnProperty, sqlalchemy.orm.descriptor_props.DescriptorProperty, sqlalchemy.orm.properties.RelationshipProperty

True if this MapperProperty refers to a mapped entity.

Should only be True for RelationshipProperty, False for all others.

@property
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