# orm/base.py # Copyright (C) 2005-2014 the SQLAlchemy authors and contributors <see AUTHORS file> # # This module is part of SQLAlchemy and is released under # the MIT License: http://www.opensource.org/licenses/mit-license.php """Constants and rudimental functions used throughout the ORM. """ from .. import util, inspection, exc as sa_exc from ..sql import expression from . import exc import operator PASSIVE_NO_RESULT = util.symbol('PASSIVE_NO_RESULT', """Symbol returned by a loader callable or other attribute/history retrieval operation when a value could not be determined, based on loader callable flags. """ ) ATTR_WAS_SET = util.symbol('ATTR_WAS_SET', """Symbol returned by a loader callable to indicate the retrieved value, or values, were assigned to their attributes on the target object. """) ATTR_EMPTY = util.symbol('ATTR_EMPTY', """Symbol used internally to indicate an attribute had no callable. """) NO_VALUE = util.symbol('NO_VALUE', """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. """ ) NEVER_SET = util.symbol('NEVER_SET', """Symbol which may be placed as the 'previous' value of an attribute indicating that the attribute had not been assigned to previously. """ ) NO_CHANGE = util.symbol("NO_CHANGE", """No callables or SQL should be emitted on attribute access and no state should change""", canonical=0 ) CALLABLES_OK = util.symbol("CALLABLES_OK", """Loader callables can be fired off if a value is not present.""", canonical=1 ) SQL_OK = util.symbol("SQL_OK", """Loader callables can emit SQL at least on scalar value attributes.""", canonical=2) RELATED_OBJECT_OK = util.symbol("RELATED_OBJECT_OK", """callables can use SQL to load related objects as well as scalar value attributes. """, canonical=4 ) INIT_OK = util.symbol("INIT_OK", """Attributes should be initialized with a blank value (None or an empty collection) upon get, if no other value can be obtained. """, canonical=8 ) NON_PERSISTENT_OK = util.symbol("NON_PERSISTENT_OK", """callables can be emitted if the parent is not persistent.""", canonical=16 ) LOAD_AGAINST_COMMITTED = util.symbol("LOAD_AGAINST_COMMITTED", """callables should use committed values as primary/foreign keys during a load """, canonical=32 ) NO_AUTOFLUSH = util.symbol("NO_AUTOFLUSH", """loader callables should disable autoflush. """, canonical=64) # pre-packaged sets of flags used as inputs PASSIVE_OFF = util.symbol("PASSIVE_OFF", "Callables can be emitted in all cases.", canonical=(RELATED_OBJECT_OK | NON_PERSISTENT_OK | INIT_OK | CALLABLES_OK | SQL_OK) ) PASSIVE_RETURN_NEVER_SET = util.symbol("PASSIVE_RETURN_NEVER_SET", """PASSIVE_OFF ^ INIT_OK""", canonical=PASSIVE_OFF ^ INIT_OK ) PASSIVE_NO_INITIALIZE = util.symbol("PASSIVE_NO_INITIALIZE", "PASSIVE_RETURN_NEVER_SET ^ CALLABLES_OK", canonical=PASSIVE_RETURN_NEVER_SET ^ CALLABLES_OK ) PASSIVE_NO_FETCH = util.symbol("PASSIVE_NO_FETCH", "PASSIVE_OFF ^ SQL_OK", canonical=PASSIVE_OFF ^ SQL_OK ) PASSIVE_NO_FETCH_RELATED = util.symbol("PASSIVE_NO_FETCH_RELATED", "PASSIVE_OFF ^ RELATED_OBJECT_OK", canonical=PASSIVE_OFF ^ RELATED_OBJECT_OK ) PASSIVE_ONLY_PERSISTENT = util.symbol("PASSIVE_ONLY_PERSISTENT", "PASSIVE_OFF ^ NON_PERSISTENT_OK", canonical=PASSIVE_OFF ^ NON_PERSISTENT_OK ) DEFAULT_MANAGER_ATTR = '_sa_class_manager' DEFAULT_STATE_ATTR = '_sa_instance_state' _INSTRUMENTOR = ('mapper', 'instrumentor') EXT_CONTINUE = util.symbol('EXT_CONTINUE') EXT_STOP = util.symbol('EXT_STOP') ONETOMANY = util.symbol('ONETOMANY', """Indicates the one-to-many direction for a :func:`.relationship`. This symbol is typically used by the internals but may be exposed within certain API features. """) MANYTOONE = util.symbol('MANYTOONE', """Indicates the many-to-one direction for a :func:`.relationship`. This symbol is typically used by the internals but may be exposed within certain API features. """) MANYTOMANY = util.symbol('MANYTOMANY', """Indicates the many-to-many direction for a :func:`.relationship`. This symbol is typically used by the internals but may be exposed within certain API features. """) NOT_EXTENSION = util.symbol('NOT_EXTENSION', """Symbol indicating an :class:`_InspectionAttr` that's not part of sqlalchemy.ext. Is assigned to the :attr:`._InspectionAttr.extension_type` attibute. """) _none_set = frozenset([None]) def _generative(*assertions): """Mark a method as generative, e.g. method-chained.""" @util.decorator def generate(fn, *args, **kw): self = args[0]._clone() for assertion in assertions: assertion(self, fn.__name__) fn(self, *args[1:], **kw) return self return generate # these can be replaced by sqlalchemy.ext.instrumentation # if augmented class instrumentation is enabled. def manager_of_class(cls): return cls.__dict__.get(DEFAULT_MANAGER_ATTR, None) instance_state = operator.attrgetter(DEFAULT_STATE_ATTR) instance_dict = operator.attrgetter('__dict__') def instance_str(instance): """Return a string describing an instance.""" return state_str(instance_state(instance)) def state_str(state): """Return a string describing an instance via its InstanceState.""" if state is None: return "None" else: return '<%s at 0x%x>' % (state.class_.__name__, id(state.obj())) def state_class_str(state): """Return a string describing an instance's class via its InstanceState.""" if state is None: return "None" else: return '<%s>' % (state.class_.__name__, ) def attribute_str(instance, attribute): return instance_str(instance) + "." + attribute def state_attribute_str(state, attribute): return state_str(state) + "." + attribute def object_mapper(instance): """Given an object, return the primary Mapper associated with the object instance. Raises :class:`sqlalchemy.orm.exc.UnmappedInstanceError` if no mapping is configured. This function is available via the inspection system as:: inspect(instance).mapper Using the inspection system will raise :class:`sqlalchemy.exc.NoInspectionAvailable` if the instance is not part of a mapping. """ return object_state(instance).mapper def object_state(instance): """Given an object, return the :class:`.InstanceState` associated with the object. Raises :class:`sqlalchemy.orm.exc.UnmappedInstanceError` if no mapping is configured. Equivalent functionality is available via the :func:`.inspect` function as:: inspect(instance) Using the inspection system will raise :class:`sqlalchemy.exc.NoInspectionAvailable` if the instance is not part of a mapping. """ state = _inspect_mapped_object(instance) if state is None: raise exc.UnmappedInstanceError(instance) else: return state @inspection._inspects(object) def _inspect_mapped_object(instance): try: return instance_state(instance) # TODO: whats the py-2/3 syntax to catch two # different kinds of exceptions at once ? except exc.UnmappedClassError: return None except exc.NO_STATE: return None def _class_to_mapper(class_or_mapper): insp = inspection.inspect(class_or_mapper, False) if insp is not None: return insp.mapper else: raise exc.UnmappedClassError(class_or_mapper) def _mapper_or_none(entity): """Return the :class:`.Mapper` for the given class or None if the class is not mapped.""" insp = inspection.inspect(entity, False) if insp is not None: return insp.mapper else: return None def _is_mapped_class(entity): """Return True if the given object is a mapped class, :class:`.Mapper`, or :class:`.AliasedClass`.""" insp = inspection.inspect(entity, False) return insp is not None and \ hasattr(insp, "mapper") and \ ( insp.is_mapper or insp.is_aliased_class ) def _attr_as_key(attr): if hasattr(attr, 'key'): return attr.key else: return expression._column_as_key(attr) def _orm_columns(entity): insp = inspection.inspect(entity, False) if hasattr(insp, 'selectable'): return [c for c in insp.selectable.c] else: return [entity] def _is_aliased_class(entity): insp = inspection.inspect(entity, False) return insp is not None and \ getattr(insp, "is_aliased_class", False) def _entity_descriptor(entity, key): """Return a class attribute given an entity and string name. May return :class:`.InstrumentedAttribute` or user-defined attribute. """ insp = inspection.inspect(entity) if insp.is_selectable: description = entity entity = insp.c elif insp.is_aliased_class: entity = insp.entity description = entity elif hasattr(insp, "mapper"): description = entity = insp.mapper.class_ else: description = entity try: return getattr(entity, key) except AttributeError: raise sa_exc.InvalidRequestError( "Entity '%s' has no property '%s'" % (description, key) ) _state_mapper = util.dottedgetter('manager.mapper') @inspection._inspects(type) def _inspect_mapped_class(class_, configure=False): try: class_manager = manager_of_class(class_) if not class_manager.is_mapped: return None mapper = class_manager.mapper if configure and mapper._new_mappers: mapper._configure_all() return mapper except exc.NO_STATE: return None def class_mapper(class_, configure=True): """Given a class, return the primary :class:`.Mapper` associated with the key. Raises :exc:`.UnmappedClassError` if no mapping is configured on the given class, or :exc:`.ArgumentError` if a non-class object is passed. Equivalent functionality is available via the :func:`.inspect` function as:: inspect(some_mapped_class) Using the inspection system will raise :class:`sqlalchemy.exc.NoInspectionAvailable` if the class is not mapped. """ mapper = _inspect_mapped_class(class_, configure=configure) if mapper is None: if not isinstance(class_, type): raise sa_exc.ArgumentError( "Class object expected, got '%r'." % (class_, )) raise exc.UnmappedClassError(class_) else: return mapper class _InspectionAttr(object): """A base class applied to all ORM objects that can be returned by the :func:`.inspect` function. The attributes defined here allow the usage of simple boolean checks to test basic facts about the object returned. 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. """ is_selectable = False """Return True if this object is an instance of :class:`.Selectable`.""" is_aliased_class = False """True if this object is an instance of :class:`.AliasedClass`.""" is_instance = False """True if this object is an instance of :class:`.InstanceState`.""" is_mapper = False """True if this object is an instance of :class:`.Mapper`.""" is_property = False """True if this object is an instance of :class:`.MapperProperty`.""" is_attribute = False """True if this object is a Python :term:`descriptor`. This can refer to one of many types. Usually a :class:`.QueryableAttribute` which handles attributes events on behalf of a :class:`.MapperProperty`. But can also be an extension type such as :class:`.AssociationProxy` or :class:`.hybrid_property`. The :attr:`._InspectionAttr.extension_type` will refer to a constant identifying the specific subtype. .. seealso:: :attr:`.Mapper.all_orm_descriptors` """ is_clause_element = False """True if this object is an instance of :class:`.ClauseElement`.""" extension_type = NOT_EXTENSION """The extension type, if any. Defaults to :data:`.interfaces.NOT_EXTENSION` .. versionadded:: 0.8.0 .. seealso:: :data:`.HYBRID_METHOD` :data:`.HYBRID_PROPERTY` :data:`.ASSOCIATION_PROXY` """ class _MappedAttribute(object): """Mixin for attributes which should be replaced by mapper-assigned attributes. """