sqlalchemy.orm.strategy

class documentation

class Load(Generative, LoaderOption):

Known subclasses: sqlalchemy.orm.strategy_options._UnboundLoad

Represents loader options which modify the state of a _query.Query in order to affect how various mapped attributes are loaded.

The _orm.Load object is in most cases used implicitly behind the scenes when one makes use of a query option like _orm.joinedload, .defer, or similar. However, the _orm.Load object can also be used directly, and in some cases can be useful.

To use _orm.Load directly, instantiate it with the target mapped class as the argument. This style of usage is useful when dealing with a _query.Query that has multiple entities:

myopt = Load(MyClass).joinedload("widgets")

The above myopt can now be used with _query.Query.options, where it will only take effect for the MyClass entity:

session.query(MyClass, MyOtherClass).options(myopt)

One case where _orm.Load is useful as public API is when specifying "wildcard" options that only take effect for a certain class:

session.query(Order).options(Load(Order).lazyload('*'))

Above, all relationships on Order will be lazy-loaded, but other attributes on those descendant objects will load using their normal loader strategy.

See Also

:ref:`deferred_options`

:ref:`deferred_loading_w_multiple`

:ref:`relationship_loader_options`

Class Method	`for_existing_path`	Undocumented
Method	`__getstate__`	Undocumented
Method	`__init__`	Undocumented
Method	`__setstate__`	Undocumented
Method	`__str__`	Undocumented
Method	`_adjust_for_extra_criteria`	Apply the current bound parameters in a QueryContext to all occurrences "extra_criteria" stored within al this Load object; copying in place.
Method	`_apply_to_parent`	Undocumented
Method	`_chop_path`	Undocumented
Method	`_clone_for_bind_strategy`	No summary
Method	`_coerce_strat`	Undocumented
Method	`_deep_clone`	Undocumented
Method	`_generate`	Undocumented
Method	`_generate_extra_criteria`	Apply the current bound parameters in a QueryContext to the immediate "extra_criteria" stored with this Load object.
Method	`_generate_path`	Undocumented
Method	`_process`	Undocumented
Method	`_set_for_path`	Undocumented
Method	`_set_path_strategy`	Undocumented
Method	`options`	Apply a series of options as sub-options to this `_orm.Load` object.
Method	`process_compile_state`	Apply a modification to a given `.CompileState`.
Method	`process_compile_state_replaced_entities`	Apply a modification to a given `.CompileState`, given entities that were replaced by with_only_columns() or with_entities().
Method	`set_class_strategy`	Undocumented
Method	`set_column_strategy`	Undocumented
Method	`set_generic_strategy`	Undocumented
Method	`set_relationship_strategy`	Undocumented
Class Variable	`_cache_key_traversal`	Undocumented
Class Variable	`_is_strategy_option`	Undocumented
Class Variable	`is_opts_only`	Undocumented
Class Variable	`strategy`	Undocumented
Instance Variable	`_extra_criteria`	Undocumented
Instance Variable	`_of_type`	Undocumented
Instance Variable	`context`	Undocumented
Instance Variable	`is_class_strategy`	Undocumented
Instance Variable	`local_opts`	Undocumented
Instance Variable	`path`	Undocumented
Instance Variable	`propagate_to_loaders`	if True, indicate this option should be carried along to "secondary" SELECT statements that occur for relationship lazy loaders as well as attribute load / refresh operations.
Property	`_context_cache_key`	Undocumented

Inherited from CompileStateOption (via LoaderOption):

Class Variable _is_compile_state Undocumented

Inherited from HasCacheKey (via LoaderOption, CompileStateOption):

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	`__slots__`	Undocumented
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 ORMOption (via LoaderOption, CompileStateOption):

Class Variable	`__slots__`	Undocumented
Class Variable	`_is_criteria_option`	Undocumented
Class Variable	`_is_legacy_option`	Undocumented

Inherited from ExecutableOption (via LoaderOption, CompileStateOption, ORMOption):

Method	`_clone`	Create a shallow copy of this ExecutableOption.
Class Variable	`__visit_name__`	Undocumented
Class Variable	`_is_has_cache_key`	Undocumented

Inherited from HasCopyInternals (via LoaderOption, CompileStateOption, ORMOption, ExecutableOption):

Method _copy_internals Reassign internal elements to be clones of themselves.

@classmethod
def for_existing_path(cls, path):

Undocumented

def __getstate__(self):

overridden in sqlalchemy.orm.strategy_options._UnboundLoad

Undocumented

def __init__(self, entity):

overridden in sqlalchemy.orm.strategy_options._UnboundLoad

Undocumented

def __setstate__(self, state):

overridden in sqlalchemy.orm.strategy_options._UnboundLoad

Undocumented

def __str__(self):

Undocumented

def _adjust_for_extra_criteria(self, context):

Apply the current bound parameters in a QueryContext to all occurrences "extra_criteria" stored within al this Load object; copying in place.

def _apply_to_parent(self, parent, applied, bound):

overridden in sqlalchemy.orm.strategy_options._UnboundLoad

Undocumented

def _chop_path(self, to_chop, path):

overridden in sqlalchemy.orm.strategy_options._UnboundLoad

Undocumented

def _clone_for_bind_strategy(self, attr, strategy, wildcard_key, opts_only=False, opts=None):

Create an anonymous clone of the Load/_UnboundLoad that is suitable to be placed in the context / _to_bind collection of this Load object. The clone will then lose references to context/_to_bind in order to not create reference cycles.

def _coerce_strat(self, strategy):

Undocumented

def _deep_clone(self, applied, process):

overridden in sqlalchemy.orm.strategy_options._UnboundLoad

Undocumented

def _generate(self):

overrides sqlalchemy.sql.base.Generative._generate

Undocumented

def _generate_extra_criteria(self, context):

Apply the current bound parameters in a QueryContext to the immediate "extra_criteria" stored with this Load object.

Load objects are typically pulled from the cached version of the statement from a QueryContext. The statement currently being executed will have new values (and keys) for bound parameters in the extra criteria which need to be applied by loader strategies when they handle this criteria for a result set.

def _generate_path(self, path, attr, for_strategy, wildcard_key, raiseerr=True, polymorphic_entity_context=None):

overridden in sqlalchemy.orm.strategy_options._UnboundLoad

Undocumented

def _process(self, compile_state, mapper_entities, raiseerr):

overridden in sqlalchemy.orm.strategy_options._UnboundLoad

Undocumented

def _set_for_path(self, context, path, replace=True, merge_opts=False):

Undocumented

def _set_path_strategy(self):

overridden in sqlalchemy.orm.strategy_options._UnboundLoad

Undocumented

@_generative
def options(self, *opts):

Apply a series of options as sub-options to this _orm.Load object.

E.g.:

query = session.query(Author)
query = query.options(
            joinedload(Author.book).options(
                load_only(Book.summary, Book.excerpt),
                joinedload(Book.citations).options(
                    joinedload(Citation.author)
                )
            )
        )

New in version 1.3.6.

See Also

.defaultload

:ref:`relationship_loader_options`

:ref:`deferred_loading_w_multiple`

Parameters
*opts	A series of loader option objects (ultimately `_orm.Load` objects) which should be applied to the path specified by this `_orm.Load` object.

def process_compile_state(self, compile_state):

overrides sqlalchemy.orm.interfaces.LoaderOption.process_compile_state

Apply a modification to a given .CompileState.

def process_compile_state_replaced_entities(self, compile_state, mapper_entities):

overrides sqlalchemy.orm.interfaces.LoaderOption.process_compile_state_replaced_entities

Apply a modification to a given .CompileState, given entities that were replaced by with_only_columns() or with_entities().

New in version 1.4.19.

@_generative
def set_class_strategy(self, strategy, opts):

Undocumented

@_generative
def set_column_strategy(self, attrs, strategy, opts=None, opts_only=False):

Undocumented

@_generative
def set_generic_strategy(self, attrs, strategy):

Undocumented

@_generative
def set_relationship_strategy(self, attr, strategy, propagate_to_loaders=True):

Undocumented

_cache_key_traversal =

Undocumented

_is_strategy_option: bool =

overrides sqlalchemy.orm.interfaces.ORMOption._is_strategy_option

Undocumented

is_opts_only: bool =

Undocumented

strategy =

Undocumented

_extra_criteria =

overridden in sqlalchemy.orm.strategy_options._UnboundLoad

Undocumented

_of_type =

Undocumented

context =

Undocumented

is_class_strategy: bool =

Undocumented

local_opts: dict =

overridden in sqlalchemy.orm.strategy_options._UnboundLoad

Undocumented

path =

overridden in sqlalchemy.orm.strategy_options._UnboundLoad

Undocumented

propagate_to_loaders =

overrides sqlalchemy.orm.interfaces.ORMOption.propagate_to_loaders

overridden in sqlalchemy.orm.strategy_options._UnboundLoad

if True, indicate this option should be carried along to "secondary" SELECT statements that occur for relationship lazy loaders as well as attribute load / refresh operations.

@property
_context_cache_key =

Undocumented

sqlalchemy.orm.strategy_options.Load

`sqlalchemy.orm.strategy_options.Load`