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Diffstat (limited to 'lib/sqlalchemy/orm/descriptor_props.py')
| -rw-r--r-- | lib/sqlalchemy/orm/descriptor_props.py | 745 |
1 files changed, 745 insertions, 0 deletions
diff --git a/lib/sqlalchemy/orm/descriptor_props.py b/lib/sqlalchemy/orm/descriptor_props.py new file mode 100644 index 0000000..3d7f23b --- /dev/null +++ b/lib/sqlalchemy/orm/descriptor_props.py @@ -0,0 +1,745 @@ +# orm/descriptor_props.py +# Copyright (C) 2005-2022 the SQLAlchemy authors and contributors +# <see AUTHORS file> +# +# This module is part of SQLAlchemy and is released under +# the MIT License: https://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 . import attributes +from . import util as orm_util +from .interfaces import MapperProperty +from .interfaces import PropComparator +from .util import _none_set +from .. import event +from .. import exc as sa_exc +from .. import schema +from .. import sql +from .. import util +from ..sql import expression +from ..sql import operators + + +class DescriptorProperty(MapperProperty): + """:class:`.MapperProperty` which proxies access to a + user-defined descriptor.""" + + doc = None + + uses_objects = False + _links_to_entity = False + + def instrument_class(self, mapper): + prop = self + + class _ProxyImpl(object): + accepts_scalar_loader = False + load_on_unexpire = True + collection = False + + @property + def uses_objects(self): + return prop.uses_objects + + 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(self.key, 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. + + .. seealso:: + + :ref:`mapper_composite` + + """ + + def __init__(self, class_, *attrs, **kwargs): + r"""Return a composite column-based property for use with a Mapper. + + See the mapping documentation section :ref:`mapper_composite` for a + full usage example. + + The :class:`.MapperProperty` returned by :func:`.composite` + is the :class:`.CompositeProperty`. + + :param class\_: + The "composite type" class, or any classmethod or callable which + will produce a new instance of the composite object given the + column values in order. + + :param \*cols: + List of Column objects to be mapped. + + :param active_history=False: + When ``True``, indicates that the "previous" value for a + scalar attribute should be loaded when replaced, if not + already loaded. See the same flag on :func:`.column_property`. + + :param group: + A group name for this property when marked as deferred. + + :param deferred: + When True, the column property is "deferred", meaning that it does + not load immediately, and is instead loaded when the attribute is + first accessed on an instance. See also + :func:`~sqlalchemy.orm.deferred`. + + :param comparator_factory: a class which extends + :class:`.CompositeProperty.Comparator` which provides custom SQL + clause generation for comparison operations. + + :param doc: + optional string that will be applied as the doc on the + class-bound descriptor. + + :param info: Optional data dictionary which will be populated into the + :attr:`.MapperProperty.info` attribute of this object. + + """ + super(CompositeProperty, self).__init__() + + 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._setup_arguments_on_columns() + + _COMPOSITE_FGET = object() + + 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, self._COMPOSITE_FGET, [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] + + @util.memoized_property + def props(self): + props = [] + for attr in self.attrs: + if isinstance(attr, str): + prop = self.parent.get_property(attr, _configure_mappers=False) + elif isinstance(attr, schema.Column): + prop = self.parent._columntoproperty[attr] + elif isinstance(attr, attributes.InstrumentedAttribute): + prop = attr.property + else: + raise sa_exc.ArgumentError( + "Composite expects Column objects or mapped " + "attributes/attribute names as arguments, got: %r" + % (attr,) + ) + props.append(prop) + return props + + @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_key = (("deferred", True), ("instrument", True)) + prop.group = self.group + + def _setup_event_handlers(self): + """Establish events that populate/expire the composite attribute.""" + + def load_handler(state, context): + _load_refresh_handler(state, context, None, is_refresh=False) + + def refresh_handler(state, context, to_load): + # note this corresponds to sqlalchemy.ext.mutable load_attrs() + + if not to_load or ( + {self.key}.union(self._attribute_keys) + ).intersection(to_load): + _load_refresh_handler(state, context, to_load, is_refresh=True) + + def _load_refresh_handler(state, context, to_load, is_refresh): + dict_ = state.dict + + # if context indicates we are coming from the + # fget() handler, this already set the value; skip the + # handler here. (other handlers like mutablecomposite will still + # want to catch it) + # there's an insufficiency here in that the fget() handler + # really should not be using the refresh event and there should + # be some other event that mutablecomposite can subscribe + # towards for this. + + if ( + not is_refresh or context is self._COMPOSITE_FGET + ) and 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 + + 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", refresh_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 CompositeBundle(orm_util.Bundle): + def __init__(self, property_, expr): + self.property = property_ + super(CompositeProperty.CompositeBundle, self).__init__( + property_.key, *expr + ) + + def create_row_processor(self, query, procs, labels): + def proc(row): + return self.property.composite_class( + *[proc(row) for proc in procs] + ) + + return proc + + 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`. + + .. seealso:: + + :class:`.PropComparator` + + :class:`.ColumnOperators` + + :ref:`types_operators` + + :attr:`.TypeEngine.comparator_factory` + + """ + + __hash__ = None + + @util.memoized_property + def clauses(self): + return expression.ClauseList( + group=False, *self._comparable_elements + ) + + def __clause_element__(self): + return self.expression + + @util.memoized_property + def expression(self): + clauses = self.clauses._annotate( + { + "parententity": self._parententity, + "parentmapper": self._parententity, + "proxy_key": self.prop.key, + } + ) + return CompositeProperty.CompositeBundle(self.prop, clauses) + + def _bulk_update_tuples(self, value): + if isinstance(value, sql.elements.BindParameter): + value = value.value + + if value is None: + values = [None for key in self.prop._attribute_keys] + elif isinstance(value, self.prop.composite_class): + values = value.__composite_values__() + else: + raise sa_exc.ArgumentError( + "Can't UPDATE composite attribute %s to %r" + % (self.prop, value) + ) + + return zip(self._comparable_elements, values) + + @util.memoized_property + def _comparable_elements(self): + if self._adapt_to_entity: + return [ + getattr(self._adapt_to_entity.entity, prop.key) + for prop 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._adapt_to_entity: + 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): + super(ConcreteInheritedProperty, self).__init__() + + 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, + info=None, + ): + """Denote an attribute name as a synonym to a mapped property, + in that the attribute will mirror the value and expression behavior + of another attribute. + + e.g.:: + + class MyClass(Base): + __tablename__ = 'my_table' + + id = Column(Integer, primary_key=True) + job_status = Column(String(50)) + + status = synonym("job_status") + + + :param name: the name of the existing mapped property. This + can refer to the string name ORM-mapped attribute + configured on the class, including column-bound attributes + and relationships. + + :param descriptor: a Python :term:`descriptor` that will be used + as a getter (and potentially a setter) when this attribute is + accessed at the instance level. + + :param map_column: **For classical mappings and mappings against + an existing Table object only**. if ``True``, the :func:`.synonym` + construct will locate the :class:`_schema.Column` + object upon the mapped + table that would normally be associated with the attribute name of + this synonym, and produce a new :class:`.ColumnProperty` that instead + maps this :class:`_schema.Column` + to the alternate name given as the "name" + argument of the synonym; in this way, the usual step of redefining + the mapping of the :class:`_schema.Column` + to be under a different name is + unnecessary. This is usually intended to be used when a + :class:`_schema.Column` + is to be replaced with an attribute that also uses a + descriptor, that is, in conjunction with the + :paramref:`.synonym.descriptor` parameter:: + + my_table = Table( + "my_table", metadata, + Column('id', Integer, primary_key=True), + Column('job_status', String(50)) + ) + + class MyClass(object): + @property + def _job_status_descriptor(self): + return "Status: %s" % self._job_status + + + mapper( + MyClass, my_table, properties={ + "job_status": synonym( + "_job_status", map_column=True, + descriptor=MyClass._job_status_descriptor) + } + ) + + Above, the attribute named ``_job_status`` is automatically + mapped to the ``job_status`` column:: + + >>> j1 = MyClass() + >>> j1._job_status = "employed" + >>> j1.job_status + Status: employed + + When using Declarative, in order to provide a descriptor in + conjunction with a synonym, use the + :func:`sqlalchemy.ext.declarative.synonym_for` helper. However, + note that the :ref:`hybrid properties <mapper_hybrids>` feature + should usually be preferred, particularly when redefining attribute + behavior. + + :param info: Optional data dictionary which will be populated into the + :attr:`.InspectionAttr.info` attribute of this object. + + .. versionadded:: 1.0.0 + + :param comparator_factory: A subclass of :class:`.PropComparator` + that will provide custom comparison behavior at the SQL expression + level. + + .. note:: + + For the use case of providing an attribute which redefines both + Python-level and SQL-expression level behavior of an attribute, + please refer to the Hybrid attribute introduced at + :ref:`mapper_hybrids` for a more effective technique. + + .. seealso:: + + :ref:`synonyms` - Overview of synonyms + + :func:`.synonym_for` - a helper oriented towards Declarative + + :ref:`mapper_hybrids` - The Hybrid Attribute extension provides an + updated approach to augmenting attribute behavior more flexibly + than can be achieved with synonyms. + + """ + super(SynonymProperty, self).__init__() + + 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 + if info: + self.info = info + + util.set_creation_order(self) + + @property + def uses_objects(self): + return getattr(self.parent.class_, self.name).impl.uses_objects + + # TODO: when initialized, check _proxied_object, + # emit a warning if its not a column-based property + + @util.memoized_property + def _proxied_object(self): + attr = getattr(self.parent.class_, self.name) + if not hasattr(attr, "property") or not isinstance( + attr.property, MapperProperty + ): + # attribute is a non-MapperProprerty proxy such as + # hybrid or association proxy + if isinstance(attr, attributes.QueryableAttribute): + return attr.comparator + elif isinstance(attr, operators.ColumnOperators): + return attr + + raise sa_exc.InvalidRequestError( + """synonym() attribute "%s.%s" only supports """ + """ORM mapped attributes, got %r""" + % (self.parent.class_.__name__, self.name, attr) + ) + return attr.property + + def _comparator_factory(self, mapper): + prop = self._proxied_object + + if isinstance(prop, MapperProperty): + if self.comparator_factory: + comp = self.comparator_factory(prop, mapper) + else: + comp = prop.comparator_factory(prop, mapper) + return comp + else: + return prop + + def get_history(self, *arg, **kw): + attr = getattr(self.parent.class_, self.name) + return attr.impl.get_history(*arg, **kw) + + @util.preload_module("sqlalchemy.orm.properties") + def set_parent(self, parent, init): + properties = util.preloaded.orm_properties + + if self.map_column: + # implement the 'map_column' option. + if self.key not in parent.persist_selectable.c: + raise sa_exc.ArgumentError( + "Can't compile synonym '%s': no column on table " + "'%s' named '%s'" + % ( + self.name, + parent.persist_selectable.description, + self.key, + ) + ) + elif ( + parent.persist_selectable.c[self.key] + in parent._columntoproperty + and parent._columntoproperty[ + parent.persist_selectable.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.persist_selectable.c[self.key] + ) + parent._configure_property(self.name, p, init=init, setparent=True) + p._mapped_by_synonym = self.key + + self.parent = parent |