679 lines
24 KiB
Python
679 lines
24 KiB
Python
# orm/descriptor_props.py
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# Copyright (C) 2005-2014 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
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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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from . import properties
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from . import query
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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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@util.langhelpers.dependency_for("sqlalchemy.orm.properties")
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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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.. seealso::
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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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"""Return a composite column-based property for use with a Mapper.
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See the mapping documentation section :ref:`mapper_composite` for a full
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usage example.
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The :class:`.MapperProperty` returned by :func:`.composite`
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is the :class:`.CompositeProperty`.
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:param class\_:
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The "composite type" class.
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:param \*cols:
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List of Column objects to be mapped.
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:param active_history=False:
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When ``True``, indicates that the "previous" value for a
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scalar attribute should be loaded when replaced, if not
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already loaded. See the same flag on :func:`.column_property`.
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.. versionchanged:: 0.7
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This flag specifically becomes meaningful
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- previously it was a placeholder.
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:param group:
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A group name for this property when marked as deferred.
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:param deferred:
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When True, the column property is "deferred", meaning that it does not
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load immediately, and is instead loaded when the attribute is first
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accessed on an instance. See also :func:`~sqlalchemy.orm.deferred`.
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:param comparator_factory: a class which extends
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:class:`.CompositeProperty.Comparator` which provides custom SQL clause
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generation for comparison operations.
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:param doc:
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optional string that will be applied as the doc on the
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class-bound descriptor.
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:param info: Optional data dictionary which will be populated into the
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:attr:`.MapperProperty.info` attribute of this object.
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.. versionadded:: 0.8
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:param extension:
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an :class:`.AttributeExtension` instance,
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or list of extensions, which will be prepended to the list of
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attribute listeners for the resulting descriptor placed on the class.
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**Deprecated.** Please see :class:`.AttributeEvents`.
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"""
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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._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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@util.memoized_property
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def props(self):
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props = []
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for attr in self.attrs:
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if isinstance(attr, str):
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prop = self.parent.get_property(attr, _configure_mappers=False)
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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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else:
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raise sa_exc.ArgumentError(
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"Composite expects Column objects or mapped "
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"attributes/attribute names as arguments, got: %r"
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% (attr,))
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props.append(prop)
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return props
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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 = prop._strategy_lookup(
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("deferred", True),
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("instrument", True))
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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 CompositeBundle(query.Bundle):
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def __init__(self, property, expr):
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self.property = property
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super(CompositeProperty.CompositeBundle, self).__init__(
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property.key, *expr)
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def create_row_processor(self, query, procs, labels):
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def proc(row, result):
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return self.property.composite_class(*[proc(row, result) for proc in procs])
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return proc
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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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__hash__ = None
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@property
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def clauses(self):
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return self.__clause_element__()
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def __clause_element__(self):
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return expression.ClauseList(group=False, *self._comparable_elements)
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def _query_clause_element(self):
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return CompositeProperty.CompositeBundle(self.prop, self.__clause_element__())
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@util.memoized_property
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def _comparable_elements(self):
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if self._adapt_to_entity:
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return [
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getattr(
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self._adapt_to_entity.entity,
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prop.key
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) for prop in self.prop._comparable_elements
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]
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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._adapt_to_entity:
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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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@util.langhelpers.dependency_for("sqlalchemy.orm.properties")
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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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@util.langhelpers.dependency_for("sqlalchemy.orm.properties")
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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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"""Denote an attribute name as a synonym to a mapped property,
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in that the attribute will mirror the value and expression behavior
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of another attribute.
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:param name: the name of the existing mapped property. This
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can refer to the string name of any :class:`.MapperProperty`
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configured on the class, including column-bound attributes
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and relationships.
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:param descriptor: a Python :term:`descriptor` that will be used
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as a getter (and potentially a setter) when this attribute is
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accessed at the instance level.
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:param map_column: if ``True``, the :func:`.synonym` construct will
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locate the existing named :class:`.MapperProperty` based on the
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attribute name of this :func:`.synonym`, and assign it to a new
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attribute linked to the name of this :func:`.synonym`.
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That is, given a mapping like::
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class MyClass(Base):
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__tablename__ = 'my_table'
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id = Column(Integer, primary_key=True)
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job_status = Column(String(50))
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job_status = synonym("_job_status", map_column=True)
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The above class ``MyClass`` will now have the ``job_status``
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:class:`.Column` object mapped to the attribute named ``_job_status``,
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and the attribute named ``job_status`` will refer to the synonym
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itself. This feature is typically used in conjunction with the
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``descriptor`` argument in order to link a user-defined descriptor
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as a "wrapper" for an existing column.
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:param comparator_factory: A subclass of :class:`.PropComparator`
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that will provide custom comparison behavior at the SQL expression
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level.
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.. note::
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For the use case of providing an attribute which redefines both
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Python-level and SQL-expression level behavior of an attribute,
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please refer to the Hybrid attribute introduced at
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:ref:`mapper_hybrids` for a more effective technique.
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.. seealso::
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:ref:`synonyms` - examples of functionality.
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:ref:`mapper_hybrids` - Hybrids provide a better approach for
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more complicated attribute-wrapping schemes than synonyms.
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"""
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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,
|
|
# 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
|
|
|
|
|
|
@util.langhelpers.dependency_for("sqlalchemy.orm.properties")
|
|
class ComparableProperty(DescriptorProperty):
|
|
"""Instruments a Python property for use in query expressions."""
|
|
|
|
def __init__(self, comparator_factory, descriptor=None, doc=None):
|
|
"""Provides a method of applying a :class:`.PropComparator`
|
|
to any Python descriptor attribute.
|
|
|
|
.. versionchanged:: 0.7
|
|
:func:`.comparable_property` is superseded by
|
|
the :mod:`~sqlalchemy.ext.hybrid` extension. See the example
|
|
at :ref:`hybrid_custom_comparators`.
|
|
|
|
Allows any Python descriptor to behave like a SQL-enabled
|
|
attribute when used at the class level in queries, allowing
|
|
redefinition of expression operator behavior.
|
|
|
|
In the example below we redefine :meth:`.PropComparator.operate`
|
|
to wrap both sides of an expression in ``func.lower()`` to produce
|
|
case-insensitive comparison::
|
|
|
|
from sqlalchemy.orm import comparable_property
|
|
from sqlalchemy.orm.interfaces import PropComparator
|
|
from sqlalchemy.sql import func
|
|
from sqlalchemy import Integer, String, Column
|
|
from sqlalchemy.ext.declarative import declarative_base
|
|
|
|
class CaseInsensitiveComparator(PropComparator):
|
|
def __clause_element__(self):
|
|
return self.prop
|
|
|
|
def operate(self, op, other):
|
|
return op(
|
|
func.lower(self.__clause_element__()),
|
|
func.lower(other)
|
|
)
|
|
|
|
Base = declarative_base()
|
|
|
|
class SearchWord(Base):
|
|
__tablename__ = 'search_word'
|
|
id = Column(Integer, primary_key=True)
|
|
word = Column(String)
|
|
word_insensitive = comparable_property(lambda prop, mapper:
|
|
CaseInsensitiveComparator(mapper.c.word, mapper)
|
|
)
|
|
|
|
|
|
A mapping like the above allows the ``word_insensitive`` attribute
|
|
to render an expression like::
|
|
|
|
>>> print SearchWord.word_insensitive == "Trucks"
|
|
lower(search_word.word) = lower(:lower_1)
|
|
|
|
:param comparator_factory:
|
|
A PropComparator subclass or factory that defines operator behavior
|
|
for this property.
|
|
|
|
:param descriptor:
|
|
Optional when used in a ``properties={}`` declaration. The Python
|
|
descriptor or property to layer comparison behavior on top of.
|
|
|
|
The like-named descriptor will be automatically retrieved from the
|
|
mapped class if left blank in a ``properties`` declaration.
|
|
|
|
"""
|
|
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)
|
|
|
|
|