# orm/descriptor_props.py
# Copyright (C) 2005-2013 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
"""Descriptor properties are more "auxiliary" properties
that exist as configurational elements, but don't participate
as actively in the load/persist ORM loop.
"""
from .interfaces import MapperProperty, PropComparator
from .util import _none_set
from . import attributes, strategies
from .. import util, sql, exc as sa_exc, event, schema
from ..sql import expression
properties = util.importlater('sqlalchemy.orm', 'properties')
class DescriptorProperty(MapperProperty):
""":class:`.MapperProperty` which proxies access to a
user-defined descriptor."""
doc = None
def instrument_class(self, mapper):
prop = self
class _ProxyImpl(object):
accepts_scalar_loader = False
expire_missing = True
collection = False
def __init__(self, key):
self.key = key
if hasattr(prop, 'get_history'):
def get_history(self, state, dict_,
passive=attributes.PASSIVE_OFF):
return prop.get_history(state, dict_, passive)
if self.descriptor is None:
desc = getattr(mapper.class_, self.key, None)
if mapper._is_userland_descriptor(desc):
self.descriptor = desc
if self.descriptor is None:
def fset(obj, value):
setattr(obj, self.name, value)
def fdel(obj):
delattr(obj, self.name)
def fget(obj):
return getattr(obj, self.name)
self.descriptor = property(
fget=fget,
fset=fset,
fdel=fdel,
)
proxy_attr = attributes.\
create_proxied_attribute(self.descriptor)\
(
self.parent.class_,
self.key,
self.descriptor,
lambda: self._comparator_factory(mapper),
doc=self.doc,
original_property=self
)
proxy_attr.impl = _ProxyImpl(self.key)
mapper.class_manager.instrument_attribute(self.key, proxy_attr)
class CompositeProperty(DescriptorProperty):
"""Defines a "composite" mapped attribute, representing a collection
of columns as one attribute.
:class:`.CompositeProperty` is constructed using the :func:`.composite`
function.
See also:
:ref:`mapper_composite`
"""
def __init__(self, class_, *attrs, **kwargs):
self.attrs = attrs
self.composite_class = class_
self.active_history = kwargs.get('active_history', False)
self.deferred = kwargs.get('deferred', False)
self.group = kwargs.get('group', None)
self.comparator_factory = kwargs.pop('comparator_factory',
self.__class__.Comparator)
if 'info' in kwargs:
self.info = kwargs.pop('info')
util.set_creation_order(self)
self._create_descriptor()
def instrument_class(self, mapper):
super(CompositeProperty, self).instrument_class(mapper)
self._setup_event_handlers()
def do_init(self):
"""Initialization which occurs after the :class:`.CompositeProperty`
has been associated with its parent mapper.
"""
self._init_props()
self._setup_arguments_on_columns()
def _create_descriptor(self):
"""Create the Python descriptor that will serve as
the access point on instances of the mapped class.
"""
def fget(instance):
dict_ = attributes.instance_dict(instance)
state = attributes.instance_state(instance)
if self.key not in dict_:
# key not present. Iterate through related
# attributes, retrieve their values. This
# ensures they all load.
values = [
getattr(instance, key)
for key in self._attribute_keys
]
# current expected behavior here is that the composite is
# created on access if the object is persistent or if
# col attributes have non-None. This would be better
# if the composite were created unconditionally,
# but that would be a behavioral change.
if self.key not in dict_ and (
state.key is not None or
not _none_set.issuperset(values)
):
dict_[self.key] = self.composite_class(*values)
state.manager.dispatch.refresh(state, None, [self.key])
return dict_.get(self.key, None)
def fset(instance, value):
dict_ = attributes.instance_dict(instance)
state = attributes.instance_state(instance)
attr = state.manager[self.key]
previous = dict_.get(self.key, attributes.NO_VALUE)
for fn in attr.dispatch.set:
value = fn(state, value, previous, attr.impl)
dict_[self.key] = value
if value is None:
for key in self._attribute_keys:
setattr(instance, key, None)
else:
for key, value in zip(
self._attribute_keys,
value.__composite_values__()):
setattr(instance, key, value)
def fdel(instance):
state = attributes.instance_state(instance)
dict_ = attributes.instance_dict(instance)
previous = dict_.pop(self.key, attributes.NO_VALUE)
attr = state.manager[self.key]
attr.dispatch.remove(state, previous, attr.impl)
for key in self._attribute_keys:
setattr(instance, key, None)
self.descriptor = property(fget, fset, fdel)
@util.memoized_property
def _comparable_elements(self):
return [
getattr(self.parent.class_, prop.key)
for prop in self.props
]
def _init_props(self):
self.props = props = []
for attr in self.attrs:
if isinstance(attr, basestring):
prop = self.parent.get_property(attr)
elif isinstance(attr, schema.Column):
prop = self.parent._columntoproperty[attr]
elif isinstance(attr, attributes.InstrumentedAttribute):
prop = attr.property
props.append(prop)
@property
def columns(self):
return [a for a in self.attrs if isinstance(a, schema.Column)]
def _setup_arguments_on_columns(self):
"""Propagate configuration arguments made on this composite
to the target columns, for those that apply.
"""
for prop in self.props:
prop.active_history = self.active_history
if self.deferred:
prop.deferred = self.deferred
prop.strategy_class = strategies.DeferredColumnLoader
prop.group = self.group
def _setup_event_handlers(self):
"""Establish events that populate/expire the composite attribute."""
def load_handler(state, *args):
dict_ = state.dict
if self.key in dict_:
return
# if column elements aren't loaded, skip.
# __get__() will initiate a load for those
# columns
for k in self._attribute_keys:
if k not in dict_:
return
#assert self.key not in dict_
dict_[self.key] = self.composite_class(
*[state.dict[key] for key in
self._attribute_keys]
)
def expire_handler(state, keys):
if keys is None or set(self._attribute_keys).intersection(keys):
state.dict.pop(self.key, None)
def insert_update_handler(mapper, connection, state):
"""After an insert or update, some columns may be expired due
to server side defaults, or re-populated due to client side
defaults. Pop out the composite value here so that it
recreates.
"""
state.dict.pop(self.key, None)
event.listen(self.parent, 'after_insert',
insert_update_handler, raw=True)
event.listen(self.parent, 'after_update',
insert_update_handler, raw=True)
event.listen(self.parent, 'load',
load_handler, raw=True, propagate=True)
event.listen(self.parent, 'refresh',
load_handler, raw=True, propagate=True)
event.listen(self.parent, 'expire',
expire_handler, raw=True, propagate=True)
# TODO: need a deserialize hook here
@util.memoized_property
def _attribute_keys(self):
return [
prop.key for prop in self.props
]
def get_history(self, state, dict_, passive=attributes.PASSIVE_OFF):
"""Provided for userland code that uses attributes.get_history()."""
added = []
deleted = []
has_history = False
for prop in self.props:
key = prop.key
hist = state.manager[key].impl.get_history(state, dict_)
if hist.has_changes():
has_history = True
non_deleted = hist.non_deleted()
if non_deleted:
added.extend(non_deleted)
else:
added.append(None)
if hist.deleted:
deleted.extend(hist.deleted)
else:
deleted.append(None)
if has_history:
return attributes.History(
[self.composite_class(*added)],
(),
[self.composite_class(*deleted)]
)
else:
return attributes.History(
(), [self.composite_class(*added)], ()
)
def _comparator_factory(self, mapper):
return self.comparator_factory(self, mapper)
class Comparator(PropComparator):
"""Produce boolean, comparison, and other operators for
:class:`.CompositeProperty` attributes.
See the example in :ref:`composite_operations` for an overview
of usage , as well as the documentation for :class:`.PropComparator`.
See also:
:class:`.PropComparator`
:class:`.ColumnOperators`
:ref:`types_operators`
:attr:`.TypeEngine.comparator_factory`
"""
def __clause_element__(self):
return expression.ClauseList(group=False, *self._comparable_elements)
__hash__ = None
@util.memoized_property
def _comparable_elements(self):
if self.adapter:
# we need to do a little fudging here because
# the adapter function we're given only accepts
# ColumnElements, but our prop._comparable_elements is returning
# InstrumentedAttribute, because we support the use case
# of composites that refer to relationships. The better
# solution here is to open up how AliasedClass interacts
# with PropComparators so more context is available.
return [self.adapter(x.__clause_element__())
for x in self.prop._comparable_elements]
else:
return self.prop._comparable_elements
def __eq__(self, other):
if other is None:
values = [None] * len(self.prop._comparable_elements)
else:
values = other.__composite_values__()
comparisons = [
a == b
for a, b in zip(self.prop._comparable_elements, values)
]
if self.adapter:
comparisons = [self.adapter(x) for x in comparisons]
return sql.and_(*comparisons)
def __ne__(self, other):
return sql.not_(self.__eq__(other))
def __str__(self):
return str(self.parent.class_.__name__) + "." + self.key
class ConcreteInheritedProperty(DescriptorProperty):
"""A 'do nothing' :class:`.MapperProperty` that disables
an attribute on a concrete subclass that is only present
on the inherited mapper, not the concrete classes' mapper.
Cases where this occurs include:
* When the superclass mapper is mapped against a
"polymorphic union", which includes all attributes from
all subclasses.
* When a relationship() is configured on an inherited mapper,
but not on the subclass mapper. Concrete mappers require
that relationship() is configured explicitly on each
subclass.
"""
def _comparator_factory(self, mapper):
comparator_callable = None
for m in self.parent.iterate_to_root():
p = m._props[self.key]
if not isinstance(p, ConcreteInheritedProperty):
comparator_callable = p.comparator_factory
break
return comparator_callable
def __init__(self):
def warn():
raise AttributeError("Concrete %s does not implement "
"attribute %r at the instance level. Add this "
"property explicitly to %s." %
(self.parent, self.key, self.parent))
class NoninheritedConcreteProp(object):
def __set__(s, obj, value):
warn()
def __delete__(s, obj):
warn()
def __get__(s, obj, owner):
if obj is None:
return self.descriptor
warn()
self.descriptor = NoninheritedConcreteProp()
class SynonymProperty(DescriptorProperty):
def __init__(self, name, map_column=None,
descriptor=None, comparator_factory=None,
doc=None):
self.name = name
self.map_column = map_column
self.descriptor = descriptor
self.comparator_factory = comparator_factory
self.doc = doc or (descriptor and descriptor.__doc__) or None
util.set_creation_order(self)
# TODO: when initialized, check _proxied_property,
# emit a warning if its not a column-based property
@util.memoized_property
def _proxied_property(self):
return getattr(self.parent.class_, self.name).property
def _comparator_factory(self, mapper):
prop = self._proxied_property
if self.comparator_factory:
comp = self.comparator_factory(prop, mapper)
else:
comp = prop.comparator_factory(prop, mapper)
return comp
def set_parent(self, parent, init):
if self.map_column:
# implement the 'map_column' option.
if self.key not in parent.mapped_table.c:
raise sa_exc.ArgumentError(
"Can't compile synonym '%s': no column on table "
"'%s' named '%s'"
% (self.name, parent.mapped_table.description, self.key))
elif parent.mapped_table.c[self.key] in \
parent._columntoproperty and \
parent._columntoproperty[
parent.mapped_table.c[self.key]
].key == self.name:
raise sa_exc.ArgumentError(
"Can't call map_column=True for synonym %r=%r, "
"a ColumnProperty already exists keyed to the name "
"%r for column %r" %
(self.key, self.name, self.name, self.key)
)
p = properties.ColumnProperty(parent.mapped_table.c[self.key])
parent._configure_property(
self.name, p,
init=init,
setparent=True)
p._mapped_by_synonym = self.key
self.parent = parent
class ComparableProperty(DescriptorProperty):
"""Instruments a Python property for use in query expressions."""
def __init__(self, comparator_factory, descriptor=None, doc=None):
self.descriptor = descriptor
self.comparator_factory = comparator_factory
self.doc = doc or (descriptor and descriptor.__doc__) or None
util.set_creation_order(self)
def _comparator_factory(self, mapper):
return self.comparator_factory(self, mapper)