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1# orm/exc.py
2# Copyright (C) 2005-2020 the SQLAlchemy authors and contributors
3# <see AUTHORS file>
4#
5# This module is part of SQLAlchemy and is released under
6# the MIT License: http://www.opensource.org/licenses/mit-license.php
8"""SQLAlchemy ORM exceptions."""
9from .. import exc as sa_exc
10from .. import util
13NO_STATE = (AttributeError, KeyError)
14"""Exception types that may be raised by instrumentation implementations."""
17class StaleDataError(sa_exc.SQLAlchemyError):
18 """An operation encountered database state that is unaccounted for.
20 Conditions which cause this to happen include:
22 * A flush may have attempted to update or delete rows
23 and an unexpected number of rows were matched during
24 the UPDATE or DELETE statement. Note that when
25 version_id_col is used, rows in UPDATE or DELETE statements
26 are also matched against the current known version
27 identifier.
29 * A mapped object with version_id_col was refreshed,
30 and the version number coming back from the database does
31 not match that of the object itself.
33 * A object is detached from its parent object, however
34 the object was previously attached to a different parent
35 identity which was garbage collected, and a decision
36 cannot be made if the new parent was really the most
37 recent "parent".
39 """
42ConcurrentModificationError = StaleDataError
45class FlushError(sa_exc.SQLAlchemyError):
46 """A invalid condition was detected during flush()."""
49class UnmappedError(sa_exc.InvalidRequestError):
50 """Base for exceptions that involve expected mappings not present."""
53class ObjectDereferencedError(sa_exc.SQLAlchemyError):
54 """An operation cannot complete due to an object being garbage
55 collected.
57 """
60class DetachedInstanceError(sa_exc.SQLAlchemyError):
61 """An attempt to access unloaded attributes on a
62 mapped instance that is detached."""
64 code = "bhk3"
67class UnmappedInstanceError(UnmappedError):
68 """An mapping operation was requested for an unknown instance."""
70 @util.dependencies("sqlalchemy.orm.base")
71 def __init__(self, base, obj, msg=None):
72 if not msg:
73 try:
74 base.class_mapper(type(obj))
75 name = _safe_cls_name(type(obj))
76 msg = (
77 "Class %r is mapped, but this instance lacks "
78 "instrumentation. This occurs when the instance "
79 "is created before sqlalchemy.orm.mapper(%s) "
80 "was called." % (name, name)
81 )
82 except UnmappedClassError:
83 msg = _default_unmapped(type(obj))
84 if isinstance(obj, type):
85 msg += (
86 "; was a class (%s) supplied where an instance was "
87 "required?" % _safe_cls_name(obj)
88 )
89 UnmappedError.__init__(self, msg)
91 def __reduce__(self):
92 return self.__class__, (None, self.args[0])
95class UnmappedClassError(UnmappedError):
96 """An mapping operation was requested for an unknown class."""
98 def __init__(self, cls, msg=None):
99 if not msg:
100 msg = _default_unmapped(cls)
101 UnmappedError.__init__(self, msg)
103 def __reduce__(self):
104 return self.__class__, (None, self.args[0])
107class ObjectDeletedError(sa_exc.InvalidRequestError):
108 """A refresh operation failed to retrieve the database
109 row corresponding to an object's known primary key identity.
111 A refresh operation proceeds when an expired attribute is
112 accessed on an object, or when :meth:`_query.Query.get` is
113 used to retrieve an object which is, upon retrieval, detected
114 as expired. A SELECT is emitted for the target row
115 based on primary key; if no row is returned, this
116 exception is raised.
118 The true meaning of this exception is simply that
119 no row exists for the primary key identifier associated
120 with a persistent object. The row may have been
121 deleted, or in some cases the primary key updated
122 to a new value, outside of the ORM's management of the target
123 object.
125 """
127 @util.dependencies("sqlalchemy.orm.base")
128 def __init__(self, base, state, msg=None):
129 if not msg:
130 msg = (
131 "Instance '%s' has been deleted, or its "
132 "row is otherwise not present." % base.state_str(state)
133 )
135 sa_exc.InvalidRequestError.__init__(self, msg)
137 def __reduce__(self):
138 return self.__class__, (None, self.args[0])
141class UnmappedColumnError(sa_exc.InvalidRequestError):
142 """Mapping operation was requested on an unknown column."""
145class NoResultFound(sa_exc.InvalidRequestError):
146 """A database result was required but none was found."""
149class MultipleResultsFound(sa_exc.InvalidRequestError):
150 """A single database result was required but more than one were found."""
153class LoaderStrategyException(sa_exc.InvalidRequestError):
154 """A loader strategy for an attribute does not exist."""
156 def __init__(
157 self,
158 applied_to_property_type,
159 requesting_property,
160 applies_to,
161 actual_strategy_type,
162 strategy_key,
163 ):
164 if actual_strategy_type is None:
165 sa_exc.InvalidRequestError.__init__(
166 self,
167 "Can't find strategy %s for %s"
168 % (strategy_key, requesting_property),
169 )
170 else:
171 sa_exc.InvalidRequestError.__init__(
172 self,
173 'Can\'t apply "%s" strategy to property "%s", '
174 'which is a "%s"; this loader strategy is intended '
175 'to be used with a "%s".'
176 % (
177 util.clsname_as_plain_name(actual_strategy_type),
178 requesting_property,
179 util.clsname_as_plain_name(applied_to_property_type),
180 util.clsname_as_plain_name(applies_to),
181 ),
182 )
185def _safe_cls_name(cls):
186 try:
187 cls_name = ".".join((cls.__module__, cls.__name__))
188 except AttributeError:
189 cls_name = getattr(cls, "__name__", None)
190 if cls_name is None:
191 cls_name = repr(cls)
192 return cls_name
195@util.dependencies("sqlalchemy.orm.base")
196def _default_unmapped(base, cls):
197 try:
198 mappers = base.manager_of_class(cls).mappers
199 except NO_STATE:
200 mappers = {}
201 except TypeError:
202 mappers = {}
203 name = _safe_cls_name(cls)
205 if not mappers:
206 return "Class '%s' is not mapped" % name