ORM Exceptions

SQLAlchemy ORM exceptions.

Object Name Description


alias of StaleDataError


Exception types that may be raised by instrumentation implementations.

attribute sqlalchemy.orm.exc..sqlalchemy.orm.exc.ConcurrentModificationError

alias of StaleDataError

exception sqlalchemy.orm.exc.DetachedInstanceError(*arg, **kw)

An attempt to access unloaded attributes on a mapped instance that is detached.

exception sqlalchemy.orm.exc.FlushError(*arg, **kw)

A invalid condition was detected during flush().

exception sqlalchemy.orm.exc.LoaderStrategyException(applied_to_property_type, requesting_property, applies_to, actual_strategy_type, strategy_key)

A loader strategy for an attribute does not exist.

sqlalchemy.orm.exc.NO_STATE = (<class 'AttributeError'>, <class 'KeyError'>)

Exception types that may be raised by instrumentation implementations.

exception sqlalchemy.orm.exc.ObjectDeletedError(state, msg=None)

A refresh operation failed to retrieve the database row corresponding to an object’s known primary key identity.

A refresh operation proceeds when an expired attribute is accessed on an object, or when Query.get() is used to retrieve an object which is, upon retrieval, detected as expired. A SELECT is emitted for the target row based on primary key; if no row is returned, this exception is raised.

The true meaning of this exception is simply that no row exists for the primary key identifier associated with a persistent object. The row may have been deleted, or in some cases the primary key updated to a new value, outside of the ORM’s management of the target object.

exception sqlalchemy.orm.exc.ObjectDereferencedError(*arg, **kw)

An operation cannot complete due to an object being garbage collected.

exception sqlalchemy.orm.exc.StaleDataError(*arg, **kw)

An operation encountered database state that is unaccounted for.

Conditions which cause this to happen include:

  • A flush may have attempted to update or delete rows and an unexpected number of rows were matched during the UPDATE or DELETE statement. Note that when version_id_col is used, rows in UPDATE or DELETE statements are also matched against the current known version identifier.

  • A mapped object with version_id_col was refreshed, and the version number coming back from the database does not match that of the object itself.

  • A object is detached from its parent object, however the object was previously attached to a different parent identity which was garbage collected, and a decision cannot be made if the new parent was really the most recent “parent”.

exception sqlalchemy.orm.exc.UnmappedClassError(cls, msg=None)

An mapping operation was requested for an unknown class.

exception sqlalchemy.orm.exc.UnmappedColumnError(*arg, **kw)

Mapping operation was requested on an unknown column.

exception sqlalchemy.orm.exc.UnmappedError(*arg, **kw)

Base for exceptions that involve expected mappings not present.

exception sqlalchemy.orm.exc.UnmappedInstanceError(obj, msg=None)

An mapping operation was requested for an unknown instance.