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|
# orm/interfaces.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
"""
Contains various base classes used throughout the ORM.
Defines the now deprecated ORM extension classes as well
as ORM internals.
Other than the deprecated extensions, this module and the
classes within should be considered mostly private.
"""
from itertools import chain
from sqlalchemy import exc as sa_exc
from sqlalchemy import util
from sqlalchemy.sql import expression
deque = util.importlater('collections').deque
mapperutil = util.importlater('sqlalchemy.orm', 'util')
collections = None
__all__ = (
'AttributeExtension',
'EXT_CONTINUE',
'EXT_STOP',
'ExtensionOption',
'InstrumentationManager',
'LoaderStrategy',
'MapperExtension',
'MapperOption',
'MapperProperty',
'PropComparator',
'PropertyOption',
'SessionExtension',
'StrategizedOption',
'StrategizedProperty',
'build_path',
)
EXT_CONTINUE = util.symbol('EXT_CONTINUE')
EXT_STOP = util.symbol('EXT_STOP')
ONETOMANY = util.symbol('ONETOMANY')
MANYTOONE = util.symbol('MANYTOONE')
MANYTOMANY = util.symbol('MANYTOMANY')
from deprecated_interfaces import AttributeExtension, SessionExtension, \
MapperExtension
class MapperProperty(object):
"""Manage the relationship of a ``Mapper`` to a single class
attribute, as well as that attribute as it appears on individual
instances of the class, including attribute instrumentation,
attribute access, loading behavior, and dependency calculations.
"""
cascade = ()
"""The set of 'cascade' attribute names.
This collection is checked before the 'cascade_iterator' method is called.
"""
def setup(self, context, entity, path, reduced_path, adapter, **kwargs):
"""Called by Query for the purposes of constructing a SQL statement.
Each MapperProperty associated with the target mapper processes the
statement referenced by the query context, adding columns and/or
criterion as appropriate.
"""
pass
def create_row_processor(self, selectcontext, path, reduced_path,
mapper, row, adapter):
"""Return a 3-tuple consisting of three row processing functions.
"""
return None, None, None
def cascade_iterator(self, type_, state, visited_instances=None,
halt_on=None):
"""Iterate through instances related to the given instance for
a particular 'cascade', starting with this MapperProperty.
Return an iterator3-tuples (instance, mapper, state).
Note that the 'cascade' collection on this MapperProperty is
checked first for the given type before cascade_iterator is called.
See PropertyLoader for the related instance implementation.
"""
return iter(())
def set_parent(self, parent, init):
self.parent = parent
def instrument_class(self, mapper):
raise NotImplementedError()
_compile_started = False
_compile_finished = False
def init(self):
"""Called after all mappers are created to assemble
relationships between mappers and perform other post-mapper-creation
initialization steps.
"""
self._compile_started = True
self.do_init()
self._compile_finished = True
@property
def class_attribute(self):
"""Return the class-bound descriptor corresponding to this
MapperProperty."""
return getattr(self.parent.class_, self.key)
def do_init(self):
"""Perform subclass-specific initialization post-mapper-creation
steps.
This is a template method called by the ``MapperProperty``
object's init() method.
"""
pass
def post_instrument_class(self, mapper):
"""Perform instrumentation adjustments that need to occur
after init() has completed.
"""
pass
def per_property_preprocessors(self, uow):
pass
def is_primary(self):
"""Return True if this ``MapperProperty``'s mapper is the
primary mapper for its class.
This flag is used to indicate that the ``MapperProperty`` can
define attribute instrumentation for the class at the class
level (as opposed to the individual instance level).
"""
return not self.parent.non_primary
def merge(self, session, source_state, source_dict, dest_state,
dest_dict, load, _recursive):
"""Merge the attribute represented by this ``MapperProperty``
from source to destination object"""
pass
def compare(self, operator, value, **kw):
"""Return a compare operation for the columns represented by
this ``MapperProperty`` to the given value, which may be a
column value or an instance. 'operator' is an operator from
the operators module, or from sql.Comparator.
By default uses the PropComparator attached to this MapperProperty
under the attribute name "comparator".
"""
return operator(self.comparator, value)
class PropComparator(expression.ColumnOperators):
"""Defines comparison operations for MapperProperty objects.
User-defined subclasses of :class:`.PropComparator` may be created. The
built-in Python comparison and math operator methods, such as
``__eq__()``, ``__lt__()``, ``__add__()``, can be overridden to provide
new operator behaivor. The custom :class:`.PropComparator` is passed to
the mapper property via the ``comparator_factory`` argument. In each case,
the appropriate subclass of :class:`.PropComparator` should be used::
from sqlalchemy.orm.properties import \\
ColumnProperty,\\
CompositeProperty,\\
RelationshipProperty
class MyColumnComparator(ColumnProperty.Comparator):
pass
class MyCompositeComparator(CompositeProperty.Comparator):
pass
class MyRelationshipComparator(RelationshipProperty.Comparator):
pass
"""
def __init__(self, prop, mapper, adapter=None):
self.prop = self.property = prop
self.mapper = mapper
self.adapter = adapter
def __clause_element__(self):
raise NotImplementedError("%r" % self)
def adapted(self, adapter):
"""Return a copy of this PropComparator which will use the given
adaption function on the local side of generated expressions.
"""
return self.__class__(self.prop, self.mapper, adapter)
@staticmethod
def any_op(a, b, **kwargs):
return a.any(b, **kwargs)
@staticmethod
def has_op(a, b, **kwargs):
return a.has(b, **kwargs)
@staticmethod
def of_type_op(a, class_):
return a.of_type(class_)
def of_type(self, class_):
"""Redefine this object in terms of a polymorphic subclass.
Returns a new PropComparator from which further criterion can be
evaluated.
e.g.::
query.join(Company.employees.of_type(Engineer)).\\
filter(Engineer.name=='foo')
\class_
a class or mapper indicating that criterion will be against
this specific subclass.
"""
return self.operate(PropComparator.of_type_op, class_)
def any(self, criterion=None, **kwargs):
"""Return true if this collection contains any member that meets the
given criterion.
criterion
an optional ClauseElement formulated against the member class' table
or attributes.
\**kwargs
key/value pairs corresponding to member class attribute names which
will be compared via equality to the corresponding values.
"""
return self.operate(PropComparator.any_op, criterion, **kwargs)
def has(self, criterion=None, **kwargs):
"""Return true if this element references a member which meets the
given criterion.
criterion
an optional ClauseElement formulated against the member class' table
or attributes.
\**kwargs
key/value pairs corresponding to member class attribute names which
will be compared via equality to the corresponding values.
"""
return self.operate(PropComparator.has_op, criterion, **kwargs)
class StrategizedProperty(MapperProperty):
"""A MapperProperty which uses selectable strategies to affect
loading behavior.
There is a single strategy selected by default. Alternate
strategies can be selected at Query time through the usage of
``StrategizedOption`` objects via the Query.options() method.
"""
def _get_context_strategy(self, context, reduced_path):
key = ('loaderstrategy', reduced_path)
if key in context.attributes:
cls = context.attributes[key]
try:
return self._strategies[cls]
except KeyError:
return self.__init_strategy(cls)
else:
return self.strategy
def _get_strategy(self, cls):
try:
return self._strategies[cls]
except KeyError:
return self.__init_strategy(cls)
def __init_strategy(self, cls):
self._strategies[cls] = strategy = cls(self)
strategy.init()
return strategy
def setup(self, context, entity, path, reduced_path, adapter, **kwargs):
self._get_context_strategy(context, reduced_path + (self.key,)).\
setup_query(context, entity, path,
reduced_path, adapter, **kwargs)
def create_row_processor(self, context, path, reduced_path, mapper, row, adapter):
return self._get_context_strategy(context, reduced_path + (self.key,)).\
create_row_processor(context, path,
reduced_path, mapper, row, adapter)
def do_init(self):
self._strategies = {}
self.strategy = self.__init_strategy(self.strategy_class)
def post_instrument_class(self, mapper):
if self.is_primary() and \
not mapper.class_manager._attr_has_impl(self.key):
self.strategy.init_class_attribute(mapper)
def build_path(entity, key, prev=None):
if prev:
return prev + (entity, key)
else:
return (entity, key)
def serialize_path(path):
if path is None:
return None
return zip(
[m.class_ for m in [path[i] for i in range(0, len(path), 2)]],
[path[i] for i in range(1, len(path), 2)] + [None]
)
def deserialize_path(path):
if path is None:
return None
p = tuple(chain(*[(mapperutil.class_mapper(cls), key) for cls, key in path]))
if p and p[-1] is None:
p = p[0:-1]
return p
class MapperOption(object):
"""Describe a modification to a Query."""
propagate_to_loaders = False
"""if True, indicate this option should be carried along
Query object generated by scalar or object lazy loaders.
"""
def process_query(self, query):
pass
def process_query_conditionally(self, query):
"""same as process_query(), except that this option may not
apply to the given query.
Used when secondary loaders resend existing options to a new
Query."""
self.process_query(query)
class PropertyOption(MapperOption):
"""A MapperOption that is applied to a property off the mapper or
one of its child mappers, identified by a dot-separated key. """
def __init__(self, key, mapper=None):
self.key = key
self.mapper = mapper
def process_query(self, query):
self._process(query, True)
def process_query_conditionally(self, query):
self._process(query, False)
def _process(self, query, raiseerr):
paths, mappers = self._get_paths(query, raiseerr)
if paths:
self.process_query_property(query, paths, mappers)
def process_query_property(self, query, paths, mappers):
pass
def __getstate__(self):
d = self.__dict__.copy()
d['key'] = ret = []
for token in util.to_list(self.key):
if isinstance(token, PropComparator):
ret.append((token.mapper.class_, token.key))
else:
ret.append(token)
return d
def __setstate__(self, state):
ret = []
for key in state['key']:
if isinstance(key, tuple):
cls, propkey = key
ret.append(getattr(cls, propkey))
else:
ret.append(key)
state['key'] = tuple(ret)
self.__dict__ = state
def _find_entity_prop_comparator(self, query, token, mapper, raiseerr):
if mapperutil._is_aliased_class(mapper):
searchfor = mapper
isa = False
else:
searchfor = mapperutil._class_to_mapper(mapper)
isa = True
for ent in query._mapper_entities:
if searchfor is ent.path_entity or isa \
and searchfor.common_parent(ent.path_entity):
return ent
else:
if raiseerr:
if not list(query._mapper_entities):
raise sa_exc.ArgumentError(
"Query has only expression-based entities - "
"can't find property named '%s'."
% (token, )
)
else:
raise sa_exc.ArgumentError(
"Can't find property '%s' on any entity "
"specified in this Query. Note the full path "
"from root (%s) to target entity must be specified."
% (token, ",".join(str(x) for
x in query._mapper_entities))
)
else:
return None
def _find_entity_basestring(self, query, token, raiseerr):
for ent in query._mapper_entities:
# return only the first _MapperEntity when searching
# based on string prop name. Ideally object
# attributes are used to specify more exactly.
return ent
else:
if raiseerr:
raise sa_exc.ArgumentError(
"Query has only expression-based entities - "
"can't find property named '%s'."
% (token, )
)
else:
return None
def _get_paths(self, query, raiseerr):
path = None
entity = None
l = []
mappers = []
# _current_path implies we're in a
# secondary load with an existing path
current_path = list(query._current_path)
tokens = deque(self.key)
while tokens:
token = tokens.popleft()
if isinstance(token, basestring):
sub_tokens = token.split(".", 1)
token = sub_tokens[0]
tokens.extendleft(sub_tokens[1:])
# exhaust current_path before
# matching tokens to entities
if current_path:
if current_path[1] == token:
current_path = current_path[2:]
continue
else:
return [], []
if not entity:
entity = self._find_entity_basestring(
query,
token,
raiseerr)
if entity is None:
return [], []
path_element = entity.path_entity
mapper = entity.mapper
mappers.append(mapper)
if mapper.has_property(token):
prop = mapper.get_property(token)
else:
if raiseerr:
raise sa_exc.ArgumentError(
"Can't find property named '%s' on the "
"mapped entity %s in this Query. " % (
token, mapper)
)
else:
return [], []
elif isinstance(token, PropComparator):
prop = token.property
# exhaust current_path before
# matching tokens to entities
if current_path:
if current_path[0:2] == \
[token.parententity, prop.key]:
current_path = current_path[2:]
continue
else:
return [], []
if not entity:
entity = self._find_entity_prop_comparator(
query,
prop.key,
token.parententity,
raiseerr)
if not entity:
return [], []
path_element = entity.path_entity
mapper = entity.mapper
mappers.append(prop.parent)
else:
raise sa_exc.ArgumentError(
"mapper option expects "
"string key or list of attributes")
assert prop is not None
path = build_path(path_element, prop.key, path)
l.append(path)
if getattr(token, '_of_type', None):
path_element = mapper = token._of_type
else:
path_element = mapper = getattr(prop, 'mapper', None)
if mapper is None and tokens:
raise sa_exc.ArgumentError(
"Attribute '%s' of entity '%s' does not "
"refer to a mapped entity" %
(token, entity)
)
if path_element:
path_element = path_element
if current_path:
# ran out of tokens before
# current_path was exhausted.
assert not tokens
return [], []
return l, mappers
class StrategizedOption(PropertyOption):
"""A MapperOption that affects which LoaderStrategy will be used
for an operation by a StrategizedProperty.
"""
chained = False
def process_query_property(self, query, paths, mappers):
# _get_context_strategy may receive the path in terms of a base
# mapper - e.g. options(eagerload_all(Company.employees,
# Engineer.machines)) in the polymorphic tests leads to
# "(Person, 'machines')" in the path due to the mechanics of how
# the eager strategy builds up the path
if self.chained:
for path in paths:
query._attributes[('loaderstrategy',
_reduce_path(path))] = \
self.get_strategy_class()
else:
query._attributes[('loaderstrategy',
_reduce_path(paths[-1]))] = \
self.get_strategy_class()
def get_strategy_class(self):
raise NotImplementedError()
def _reduce_path(path):
"""Convert a (mapper, path) path to use base mappers.
This is used to allow more open ended selection of loader strategies, i.e.
Mapper -> prop1 -> Subclass -> prop2, where Subclass is a sub-mapper
of the mapper referenced by Mapper.prop1.
"""
return tuple([i % 2 != 0 and
element or
getattr(element, 'base_mapper', element)
for i, element in enumerate(path)])
class LoaderStrategy(object):
"""Describe the loading behavior of a StrategizedProperty object.
The ``LoaderStrategy`` interacts with the querying process in three
ways:
* it controls the configuration of the ``InstrumentedAttribute``
placed on a class to handle the behavior of the attribute. this
may involve setting up class-level callable functions to fire
off a select operation when the attribute is first accessed
(i.e. a lazy load)
* it processes the ``QueryContext`` at statement construction time,
where it can modify the SQL statement that is being produced.
simple column attributes may add their represented column to the
list of selected columns, *eager loading* properties may add
``LEFT OUTER JOIN`` clauses to the statement.
* it processes the ``SelectionContext`` at row-processing time. This
includes straight population of attributes corresponding to rows,
setting instance-level lazyloader callables on newly
constructed instances, and appending child items to scalar/collection
attributes in response to eagerly-loaded relations.
"""
def __init__(self, parent):
self.parent_property = parent
self.is_class_level = False
self.parent = self.parent_property.parent
self.key = self.parent_property.key
def init(self):
raise NotImplementedError("LoaderStrategy")
def init_class_attribute(self, mapper):
pass
def setup_query(self, context, entity, path, reduced_path, adapter, **kwargs):
pass
def create_row_processor(self, selectcontext, path, reduced_path, mapper,
row, adapter):
"""Return row processing functions which fulfill the contract
specified by MapperProperty.create_row_processor.
StrategizedProperty delegates its create_row_processor method
directly to this method. """
return None, None, None
def __str__(self):
return str(self.parent_property)
def debug_callable(self, fn, logger, announcement, logfn):
if announcement:
logger.debug(announcement)
if logfn:
def call(*args, **kwargs):
logger.debug(logfn(*args, **kwargs))
return fn(*args, **kwargs)
return call
else:
return fn
class InstrumentationManager(object):
"""User-defined class instrumentation extension.
:class:`.InstrumentationManager` can be subclassed in order
to change
how class instrumentation proceeds. This class exists for
the purposes of integration with other object management
frameworks which would like to entirely modify the
instrumentation methodology of the ORM, and is not intended
for regular usage. For interception of class instrumentation
events, see :class:`.InstrumentationEvents`.
For an example of :class:`.InstrumentationManager`, see the
example :ref:`examples_instrumentation`.
The API for this class should be considered as semi-stable,
and may change slightly with new releases.
"""
# r4361 added a mandatory (cls) constructor to this interface.
# given that, perhaps class_ should be dropped from all of these
# signatures.
def __init__(self, class_):
pass
def manage(self, class_, manager):
setattr(class_, '_default_class_manager', manager)
def dispose(self, class_, manager):
delattr(class_, '_default_class_manager')
def manager_getter(self, class_):
def get(cls):
return cls._default_class_manager
return get
def instrument_attribute(self, class_, key, inst):
pass
def post_configure_attribute(self, class_, key, inst):
pass
def install_descriptor(self, class_, key, inst):
setattr(class_, key, inst)
def uninstall_descriptor(self, class_, key):
delattr(class_, key)
def install_member(self, class_, key, implementation):
setattr(class_, key, implementation)
def uninstall_member(self, class_, key):
delattr(class_, key)
def instrument_collection_class(self, class_, key, collection_class):
global collections
if collections is None:
from sqlalchemy.orm import collections
return collections.prepare_instrumentation(collection_class)
def get_instance_dict(self, class_, instance):
return instance.__dict__
def initialize_instance_dict(self, class_, instance):
pass
def install_state(self, class_, instance, state):
setattr(instance, '_default_state', state)
def remove_state(self, class_, instance):
delattr(instance, '_default_state')
def state_getter(self, class_):
return lambda instance: getattr(instance, '_default_state')
def dict_getter(self, class_):
return lambda inst: self.get_instance_dict(class_, inst)
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