sqlalchemy.orm.interfaces.StrategizedProperty

class documentation

class StrategizedProperty(MapperProperty):

Known subclasses: sqlalchemy.orm.properties.ColumnProperty, sqlalchemy.orm.properties.RelationshipProperty

A MapperProperty which uses selectable strategies to affect loading behavior.

There is a single strategy selected by default. Alternate strategies can be selected at Query time through the usage of StrategizedOption objects via the Query.options() method.

The mechanics of StrategizedProperty are used for every Query invocation for every mapped attribute participating in that Query, to determine first how the attribute will be rendered in SQL and secondly how the attribute will retrieve a value from a result row and apply it to a mapped object. The routines here are very performance-critical.

Class Method	`strategy_for`	Undocumented
Class Method	`_strategy_lookup`	Undocumented
Method	`_get_context_loader`	Undocumented
Method	`_get_strategy`	Undocumented
Method	`_memoized_attr__default_path_loader_key`	Undocumented
Method	`_memoized_attr__wildcard_token`	Undocumented
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	`post_instrument_class`	Perform instrumentation adjustments that need to occur after init() has completed.
Method	`setup`	Called by Query for the purposes of constructing a SQL statement.
Class Variable	`__slots__`	Undocumented
Class Variable	`_all_strategies`	Undocumented
Class Variable	`inherit_cache`	Indicate if this `.HasCacheKey` instance should make use of the cache key generation scheme used by its immediate superclass.
Class Variable	`strategy_wildcard_key`	Undocumented
Instance Variable	`_strategies`	Undocumented
Instance Variable	`strategy`	Undocumented

Inherited from MapperProperty:

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	`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	`set_parent`	Set the parent mapper that references this MapperProperty.
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 (via MapperProperty):

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 (via MapperProperty):

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 (via MapperProperty):

Method	`__getattr__`	Undocumented
Method	`_fallback_getattr`	Undocumented

@classmethod
def strategy_for(cls, **kw):

Undocumented

@classmethod
def _strategy_lookup(cls, requesting_property, *key):

Undocumented

def _get_context_loader(self, context, path):

Undocumented

def _get_strategy(self, key):

Undocumented

def _memoized_attr__default_path_loader_key(self):

Undocumented

def _memoized_attr__wildcard_token(self):

Undocumented

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

overrides sqlalchemy.orm.interfaces.MapperProperty.create_row_processor

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

def do_init(self):

overrides sqlalchemy.orm.interfaces.MapperProperty.do_init

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

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

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

def post_instrument_class(self, mapper):

overrides sqlalchemy.orm.interfaces.MapperProperty.post_instrument_class

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

overrides sqlalchemy.orm.interfaces.MapperProperty.setup

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.orm.interfaces.MapperProperty.__slots__

overridden in sqlalchemy.orm.properties.ColumnProperty

Undocumented

_all_strategies =

Undocumented

inherit_cache: bool =

overrides sqlalchemy.sql.traversals.HasCacheKey.inherit_cache

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

Indicate if this .HasCacheKey instance should make use of the cache key generation scheme used by its immediate superclass.

The attribute defaults to None, which indicates that a construct has not yet taken into account whether or not its appropriate for it to participate in caching; this is functionally equivalent to setting the value to False, except that a warning is also emitted.

This flag can be set to True on a particular class, if the SQL that corresponds to the object does not change based on attributes which are local to this class, and not its superclass.