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# orm/base.py
# Copyright (C) 2005-2016 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.
""")
_never_set = frozenset([NEVER_SET])
_none_set = frozenset([None, NEVER_SET, PASSIVE_NO_RESULT])
_SET_DEFERRED_EXPIRED = util.symbol("SET_DEFERRED_EXPIRED")
_DEFER_FOR_STATE = util.symbol("DEFER_FOR_STATE")
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 \
not insp.is_clause_element 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') and hasattr(insp.selectable, 'c'):
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
except exc.NO_STATE:
return None
else:
if configure and mapper._new_mappers:
mapper._configure_all()
return mapper
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.
"""
__slots__ = ()
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 InspectionAttrInfo(InspectionAttr):
"""Adds the ``.info`` attribute to :class:`.InspectionAttr`.
The rationale for :class:`.InspectionAttr` vs. :class:`.InspectionAttrInfo`
is that the former is compatible as a mixin for classes that specify
``__slots__``; this is essentially an implementation artifact.
"""
@util.memoized_property
def info(self):
"""Info dictionary associated with the object, allowing user-defined
data to be associated with this :class:`.InspectionAttr`.
The dictionary is generated when first accessed. Alternatively,
it can be specified as a constructor argument to the
:func:`.column_property`, :func:`.relationship`, or :func:`.composite`
functions.
.. versionadded:: 0.8 Added support for .info to all
:class:`.MapperProperty` subclasses.
.. versionchanged:: 1.0.0 :attr:`.MapperProperty.info` is also
available on extension types via the
:attr:`.InspectionAttrInfo.info` attribute, so that it can apply
to a wider variety of ORM and extension constructs.
.. seealso::
:attr:`.QueryableAttribute.info`
:attr:`.SchemaItem.info`
"""
return {}
class _MappedAttribute(object):
"""Mixin for attributes which should be replaced by mapper-assigned
attributes.
"""
__slots__ = ()
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