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# orm/util.py
# Copyright (C) 2005-2011 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
from sqlalchemy import sql, util, event, exc as sa_exc
from sqlalchemy.sql import expression, util as sql_util, operators
from sqlalchemy.orm.interfaces import MapperExtension, EXT_CONTINUE,\
PropComparator, MapperProperty
from sqlalchemy.orm import attributes, exc
import operator
mapperlib = util.importlater("sqlalchemy.orm", "mapperlib")
all_cascades = frozenset(("delete", "delete-orphan", "all", "merge",
"expunge", "save-update", "refresh-expire",
"none"))
_INSTRUMENTOR = ('mapper', 'instrumentor')
class CascadeOptions(dict):
"""Keeps track of the options sent to relationship().cascade"""
def __init__(self, arg=""):
if not arg:
values = set()
else:
values = set(c.strip() for c in arg.split(','))
for name in ['save-update', 'delete', 'refresh-expire',
'merge', 'expunge']:
boolean = name in values or 'all' in values
setattr(self, name.replace('-', '_'), boolean)
if boolean:
self[name] = True
self.delete_orphan = "delete-orphan" in values
if self.delete_orphan:
self['delete-orphan'] = True
if self.delete_orphan and not self.delete:
util.warn("The 'delete-orphan' cascade option requires "
"'delete'. This will raise an error in 0.6.")
for x in values:
if x not in all_cascades:
raise sa_exc.ArgumentError("Invalid cascade option '%s'" % x)
def __repr__(self):
return "CascadeOptions(%s)" % repr(",".join(
[x for x in ['delete', 'save_update', 'merge', 'expunge',
'delete_orphan', 'refresh-expire']
if getattr(self, x, False) is True]))
def _validator_events(desc, key, validator):
"""Runs a validation method on an attribute value to be set or appended."""
def append(state, value, initiator):
return validator(state.obj(), key, value)
def set_(state, value, oldvalue, initiator):
return validator(state.obj(), key, value)
event.listen(desc, 'append', append, raw=True, retval=True)
event.listen(desc, 'set', set_, raw=True, retval=True)
def polymorphic_union(table_map, typecolname, aliasname='p_union', cast_nulls=True):
"""Create a ``UNION`` statement used by a polymorphic mapper.
See :ref:`concrete_inheritance` for an example of how
this is used.
:param table_map: mapping of polymorphic identities to
:class:`.Table` objects.
:param typecolname: string name of a "discriminator" column, which will be
derived from the query, producing the polymorphic identity for each row. If
``None``, no polymorphic discriminator is generated.
:param aliasname: name of the :func:`~sqlalchemy.sql.expression.alias()`
construct generated.
:param cast_nulls: if True, non-existent columns, which are represented as labeled
NULLs, will be passed into CAST. This is a legacy behavior that is problematic
on some backends such as Oracle - in which case it can be set to False.
"""
colnames = util.OrderedSet()
colnamemaps = {}
types = {}
for key in table_map.keys():
table = table_map[key]
# mysql doesnt like selecting from a select;
# make it an alias of the select
if isinstance(table, sql.Select):
table = table.alias()
table_map[key] = table
m = {}
for c in table.c:
colnames.add(c.key)
m[c.key] = c
types[c.key] = c.type
colnamemaps[table] = m
def col(name, table):
try:
return colnamemaps[table][name]
except KeyError:
if cast_nulls:
return sql.cast(sql.null(), types[name]).label(name)
else:
return sql.type_coerce(sql.null(), types[name]).label(name)
result = []
for type, table in table_map.iteritems():
if typecolname is not None:
result.append(
sql.select([col(name, table) for name in colnames] +
[sql.literal_column(sql_util._quote_ddl_expr(type)).
label(typecolname)],
from_obj=[table]))
else:
result.append(sql.select([col(name, table) for name in colnames],
from_obj=[table]))
return sql.union_all(*result).alias(aliasname)
def identity_key(*args, **kwargs):
"""Get an identity key.
Valid call signatures:
* ``identity_key(class, ident)``
class
mapped class (must be a positional argument)
ident
primary key, if the key is composite this is a tuple
* ``identity_key(instance=instance)``
instance
object instance (must be given as a keyword arg)
* ``identity_key(class, row=row)``
class
mapped class (must be a positional argument)
row
result proxy row (must be given as a keyword arg)
"""
if args:
if len(args) == 1:
class_ = args[0]
try:
row = kwargs.pop("row")
except KeyError:
ident = kwargs.pop("ident")
elif len(args) == 2:
class_, ident = args
elif len(args) == 3:
class_, ident = args
else:
raise sa_exc.ArgumentError("expected up to three "
"positional arguments, got %s" % len(args))
if kwargs:
raise sa_exc.ArgumentError("unknown keyword arguments: %s"
% ", ".join(kwargs.keys()))
mapper = class_mapper(class_)
if "ident" in locals():
return mapper.identity_key_from_primary_key(ident)
return mapper.identity_key_from_row(row)
instance = kwargs.pop("instance")
if kwargs:
raise sa_exc.ArgumentError("unknown keyword arguments: %s"
% ", ".join(kwargs.keys()))
mapper = object_mapper(instance)
return mapper.identity_key_from_instance(instance)
class ORMAdapter(sql_util.ColumnAdapter):
"""Extends ColumnAdapter to accept ORM entities.
The selectable is extracted from the given entity,
and the AliasedClass if any is referenced.
"""
def __init__(self, entity, equivalents=None,
chain_to=None, adapt_required=False):
self.mapper, selectable, is_aliased_class = _entity_info(entity)
if is_aliased_class:
self.aliased_class = entity
else:
self.aliased_class = None
sql_util.ColumnAdapter.__init__(self, selectable,
equivalents, chain_to,
adapt_required=adapt_required)
def replace(self, elem):
entity = elem._annotations.get('parentmapper', None)
if not entity or entity.isa(self.mapper):
return sql_util.ColumnAdapter.replace(self, elem)
else:
return None
class AliasedClass(object):
"""Represents an "aliased" form of a mapped class for usage with Query.
The ORM equivalent of a :func:`sqlalchemy.sql.expression.alias`
construct, this object mimics the mapped class using a
__getattr__ scheme and maintains a reference to a
real :class:`~sqlalchemy.sql.expression.Alias` object.
Usage is via the :class:`~sqlalchemy.orm.aliased()` synonym::
# find all pairs of users with the same name
user_alias = aliased(User)
session.query(User, user_alias).\\
join((user_alias, User.id > user_alias.id)).\\
filter(User.name==user_alias.name)
"""
def __init__(self, cls, alias=None, name=None):
self.__mapper = _class_to_mapper(cls)
self.__target = self.__mapper.class_
if alias is None:
alias = self.__mapper._with_polymorphic_selectable.alias(name=name)
self.__adapter = sql_util.ClauseAdapter(alias,
equivalents=self.__mapper._equivalent_columns)
self.__alias = alias
# used to assign a name to the RowTuple object
# returned by Query.
self._sa_label_name = name
self.__name__ = 'AliasedClass_' + str(self.__target)
def __getstate__(self):
return {
'mapper':self.__mapper,
'alias':self.__alias,
'name':self._sa_label_name
}
def __setstate__(self, state):
self.__mapper = state['mapper']
self.__target = self.__mapper.class_
alias = state['alias']
self.__adapter = sql_util.ClauseAdapter(alias,
equivalents=self.__mapper._equivalent_columns)
self.__alias = alias
name = state['name']
self._sa_label_name = name
self.__name__ = 'AliasedClass_' + str(self.__target)
def __adapt_element(self, elem):
return self.__adapter.traverse(elem).\
_annotate({
'parententity': self,
'parentmapper':self.__mapper}
)
def __adapt_prop(self, existing, key):
comparator = existing.comparator.adapted(self.__adapt_element)
queryattr = attributes.QueryableAttribute(self, key,
impl=existing.impl, parententity=self, comparator=comparator)
setattr(self, key, queryattr)
return queryattr
def __getattr__(self, key):
for base in self.__target.__mro__:
try:
attr = object.__getattribute__(base, key)
except AttributeError:
continue
else:
break
else:
raise AttributeError(key)
if isinstance(attr, attributes.QueryableAttribute):
return self.__adapt_prop(attr, key)
elif hasattr(attr, 'func_code'):
is_method = getattr(self.__target, key, None)
if is_method and is_method.im_self is not None:
return util.types.MethodType(attr.im_func, self, self)
else:
return None
elif hasattr(attr, '__get__'):
ret = attr.__get__(None, self)
if isinstance(ret, PropComparator):
return ret.adapted(self.__adapt_element)
return ret
else:
return attr
def __repr__(self):
return '<AliasedClass at 0x%x; %s>' % (
id(self), self.__target.__name__)
def aliased(element, alias=None, name=None):
if isinstance(element, expression.FromClause):
return element.alias(name)
else:
return AliasedClass(element, alias=alias, name=name)
def _orm_annotate(element, exclude=None):
"""Deep copy the given ClauseElement, annotating each element with the
"_orm_adapt" flag.
Elements within the exclude collection will be cloned but not annotated.
"""
return sql_util._deep_annotate(element, {'_orm_adapt':True}, exclude)
_orm_deannotate = sql_util._deep_deannotate
class _ORMJoin(expression.Join):
"""Extend Join to support ORM constructs as input."""
__visit_name__ = expression.Join.__visit_name__
def __init__(self, left, right, onclause=None,
isouter=False, join_to_left=True):
adapt_from = None
if hasattr(left, '_orm_mappers'):
left_mapper = left._orm_mappers[1]
if join_to_left:
adapt_from = left.right
else:
left_mapper, left, left_is_aliased = _entity_info(left)
if join_to_left and (left_is_aliased or not left_mapper):
adapt_from = left
right_mapper, right, right_is_aliased = _entity_info(right)
if right_is_aliased:
adapt_to = right
else:
adapt_to = None
if left_mapper or right_mapper:
self._orm_mappers = (left_mapper, right_mapper)
if isinstance(onclause, basestring):
prop = left_mapper.get_property(onclause)
elif isinstance(onclause, attributes.QueryableAttribute):
if adapt_from is None:
adapt_from = onclause.__clause_element__()
prop = onclause.property
elif isinstance(onclause, MapperProperty):
prop = onclause
else:
prop = None
if prop:
pj, sj, source, dest, \
secondary, target_adapter = prop._create_joins(
source_selectable=adapt_from,
dest_selectable=adapt_to,
source_polymorphic=True,
dest_polymorphic=True,
of_type=right_mapper)
if sj is not None:
left = sql.join(left, secondary, pj, isouter)
onclause = sj
else:
onclause = pj
self._target_adapter = target_adapter
expression.Join.__init__(self, left, right, onclause, isouter)
def join(self, right, onclause=None, isouter=False, join_to_left=True):
return _ORMJoin(self, right, onclause, isouter, join_to_left)
def outerjoin(self, right, onclause=None, join_to_left=True):
return _ORMJoin(self, right, onclause, True, join_to_left)
def join(left, right, onclause=None, isouter=False, join_to_left=True):
"""Produce an inner join between left and right clauses.
In addition to the interface provided by
:func:`~sqlalchemy.sql.expression.join()`, left and right may be mapped
classes or AliasedClass instances. The onclause may be a
string name of a relationship(), or a class-bound descriptor
representing a relationship.
join_to_left indicates to attempt aliasing the ON clause,
in whatever form it is passed, to the selectable
passed as the left side. If False, the onclause
is used as is.
"""
return _ORMJoin(left, right, onclause, isouter, join_to_left)
def outerjoin(left, right, onclause=None, join_to_left=True):
"""Produce a left outer join between left and right clauses.
In addition to the interface provided by
:func:`~sqlalchemy.sql.expression.outerjoin()`, left and right may be
mapped classes or AliasedClass instances. The onclause may be a string
name of a relationship(), or a class-bound descriptor representing a
relationship.
"""
return _ORMJoin(left, right, onclause, True, join_to_left)
def with_parent(instance, prop):
"""Create filtering criterion that relates this query's primary entity
to the given related instance, using established :func:`.relationship()`
configuration.
The SQL rendered is the same as that rendered when a lazy loader
would fire off from the given parent on that attribute, meaning
that the appropriate state is taken from the parent object in
Python without the need to render joins to the parent table
in the rendered statement.
As of 0.6.4, this method accepts parent instances in all
persistence states, including transient, persistent, and detached.
Only the requisite primary key/foreign key attributes need to
be populated. Previous versions didn't work with transient
instances.
:param instance:
An instance which has some :func:`.relationship`.
:param property:
String property name, or class-bound attribute, which indicates
what relationship from the instance should be used to reconcile the
parent/child relationship.
"""
if isinstance(prop, basestring):
mapper = object_mapper(instance)
prop = mapper.get_property(prop)
elif isinstance(prop, attributes.QueryableAttribute):
prop = prop.property
return prop.compare(operators.eq,
instance,
value_is_parent=True)
def _entity_info(entity, compile=True):
"""Return mapping information given a class, mapper, or AliasedClass.
Returns 3-tuple of: mapper, mapped selectable, boolean indicating if this
is an aliased() construct.
If the given entity is not a mapper, mapped class, or aliased construct,
returns None, the entity, False. This is typically used to allow
unmapped selectables through.
"""
if isinstance(entity, AliasedClass):
return entity._AliasedClass__mapper, entity._AliasedClass__alias, True
if isinstance(entity, mapperlib.Mapper):
mapper = entity
elif isinstance(entity, type):
class_manager = attributes.manager_of_class(entity)
if class_manager is None:
return None, entity, False
mapper = class_manager.mapper
else:
return None, entity, False
if compile and mapperlib.module._new_mappers:
mapperlib.configure_mappers()
return mapper, mapper._with_polymorphic_selectable, False
def _entity_descriptor(entity, key):
"""Return a class attribute given an entity and string name.
May return :class:`.InstrumentedAttribute` or user-defined
attribute.
"""
if not isinstance(entity, (AliasedClass, type)):
entity = entity.class_
try:
return getattr(entity, key)
except AttributeError:
raise sa_exc.InvalidRequestError(
"Entity '%s' has no property '%s'" %
(entity, key)
)
def _orm_columns(entity):
mapper, selectable, is_aliased_class = _entity_info(entity)
if isinstance(selectable, expression.Selectable):
return [c for c in selectable.c]
else:
return [selectable]
def _orm_selectable(entity):
mapper, selectable, is_aliased_class = _entity_info(entity)
return selectable
def _attr_as_key(attr):
if hasattr(attr, 'key'):
return attr.key
else:
return expression._column_as_key(attr)
def _is_aliased_class(entity):
return isinstance(entity, AliasedClass)
_state_mapper = util.dottedgetter('manager.mapper')
def object_mapper(instance):
"""Given an object, return the primary Mapper associated with the object
instance.
Raises UnmappedInstanceError if no mapping is configured.
"""
try:
state = attributes.instance_state(instance)
return state.manager.mapper
except exc.UnmappedClassError:
raise exc.UnmappedInstanceError(instance)
except exc.NO_STATE:
raise exc.UnmappedInstanceError(instance)
def class_mapper(class_, compile=True):
"""Given a class, return the primary Mapper associated with the key.
Raises UnmappedClassError if no mapping is configured.
"""
try:
class_manager = attributes.manager_of_class(class_)
mapper = class_manager.mapper
except exc.NO_STATE:
raise exc.UnmappedClassError(class_)
if compile and mapperlib.module._new_mappers:
mapperlib.configure_mappers()
return mapper
def _class_to_mapper(class_or_mapper, compile=True):
if _is_aliased_class(class_or_mapper):
return class_or_mapper._AliasedClass__mapper
elif isinstance(class_or_mapper, type):
try:
class_manager = attributes.manager_of_class(class_or_mapper)
mapper = class_manager.mapper
except exc.NO_STATE:
raise exc.UnmappedClassError(class_or_mapper)
elif isinstance(class_or_mapper, mapperlib.Mapper):
mapper = class_or_mapper
else:
raise exc.UnmappedClassError(class_or_mapper)
if compile and mapperlib.module._new_mappers:
mapperlib.configure_mappers()
return mapper
def has_identity(object):
state = attributes.instance_state(object)
return state.has_identity
def _is_mapped_class(cls):
if isinstance(cls, (AliasedClass, mapperlib.Mapper)):
return True
if isinstance(cls, expression.ClauseElement):
return False
if isinstance(cls, type):
manager = attributes.manager_of_class(cls)
return manager and _INSTRUMENTOR in manager.info
return False
def instance_str(instance):
"""Return a string describing an instance."""
return state_str(attributes.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 identity_equal(a, b):
if a is b:
return True
if a is None or b is None:
return False
try:
state_a = attributes.instance_state(a)
state_b = attributes.instance_state(b)
except exc.NO_STATE:
return False
if state_a.key is None or state_b.key is None:
return False
return state_a.key == state_b.key
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