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