278 lines
10 KiB
Python
278 lines
10 KiB
Python
# orm/properties.py
|
|
# Copyright (C) 2005-2018 the SQLAlchemy authors and contributors
|
|
# <see AUTHORS file>
|
|
#
|
|
# This module is part of SQLAlchemy and is released under
|
|
# the MIT License: http://www.opensource.org/licenses/mit-license.php
|
|
|
|
"""MapperProperty implementations.
|
|
|
|
This is a private module which defines the behavior of invidual ORM-
|
|
mapped attributes.
|
|
|
|
"""
|
|
from __future__ import absolute_import
|
|
|
|
from .. import util, log
|
|
from ..sql import expression
|
|
from . import attributes
|
|
from .util import _orm_full_deannotate
|
|
|
|
from .interfaces import PropComparator, StrategizedProperty
|
|
|
|
__all__ = ['ColumnProperty', 'CompositeProperty', 'SynonymProperty',
|
|
'ComparableProperty', 'RelationshipProperty']
|
|
|
|
|
|
@log.class_logger
|
|
class ColumnProperty(StrategizedProperty):
|
|
"""Describes an object attribute that corresponds to a table column.
|
|
|
|
Public constructor is the :func:`.orm.column_property` function.
|
|
|
|
"""
|
|
|
|
strategy_wildcard_key = 'column'
|
|
|
|
__slots__ = (
|
|
'_orig_columns', 'columns', 'group', 'deferred',
|
|
'instrument', 'comparator_factory', 'descriptor', 'extension',
|
|
'active_history', 'expire_on_flush', 'info', 'doc',
|
|
'strategy_key', '_creation_order', '_is_polymorphic_discriminator',
|
|
'_mapped_by_synonym', '_deferred_column_loader')
|
|
|
|
def __init__(self, *columns, **kwargs):
|
|
r"""Provide a column-level property for use with a Mapper.
|
|
|
|
Column-based properties can normally be applied to the mapper's
|
|
``properties`` dictionary using the :class:`.Column` element directly.
|
|
Use this function when the given column is not directly present within
|
|
the mapper's selectable; examples include SQL expressions, functions,
|
|
and scalar SELECT queries.
|
|
|
|
Columns that aren't present in the mapper's selectable won't be
|
|
persisted by the mapper and are effectively "read-only" attributes.
|
|
|
|
: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. Normally, history tracking logic for
|
|
simple non-primary-key scalar values only needs to be
|
|
aware of the "new" value in order to perform a flush. This
|
|
flag is available for applications that make use of
|
|
:func:`.attributes.get_history` or :meth:`.Session.is_modified`
|
|
which also need to know
|
|
the "previous" value of the attribute.
|
|
|
|
.. versionadded:: 0.6.6
|
|
|
|
:param comparator_factory: a class which extends
|
|
:class:`.ColumnProperty.Comparator` which provides custom SQL
|
|
clause generation for comparison operations.
|
|
|
|
: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 doc:
|
|
optional string that will be applied as the doc on the
|
|
class-bound descriptor.
|
|
|
|
:param expire_on_flush=True:
|
|
Disable expiry on flush. A column_property() which refers
|
|
to a SQL expression (and not a single table-bound column)
|
|
is considered to be a "read only" property; populating it
|
|
has no effect on the state of data, and it can only return
|
|
database state. For this reason a column_property()'s value
|
|
is expired whenever the parent object is involved in a
|
|
flush, that is, has any kind of "dirty" state within a flush.
|
|
Setting this parameter to ``False`` will have the effect of
|
|
leaving any existing value present after the flush proceeds.
|
|
Note however that the :class:`.Session` with default expiration
|
|
settings still expires
|
|
all attributes after a :meth:`.Session.commit` call, however.
|
|
|
|
.. versionadded:: 0.7.3
|
|
|
|
:param info: Optional data dictionary which will be populated into the
|
|
:attr:`.MapperProperty.info` attribute of this object.
|
|
|
|
.. versionadded:: 0.8
|
|
|
|
:param extension:
|
|
an
|
|
:class:`.AttributeExtension`
|
|
instance, or list of extensions, which will be prepended
|
|
to the list of attribute listeners for the resulting
|
|
descriptor placed on the class.
|
|
**Deprecated.** Please see :class:`.AttributeEvents`.
|
|
|
|
"""
|
|
super(ColumnProperty, self).__init__()
|
|
self._orig_columns = [expression._labeled(c) for c in columns]
|
|
self.columns = [expression._labeled(_orm_full_deannotate(c))
|
|
for c in columns]
|
|
self.group = kwargs.pop('group', None)
|
|
self.deferred = kwargs.pop('deferred', False)
|
|
self.instrument = kwargs.pop('_instrument', True)
|
|
self.comparator_factory = kwargs.pop('comparator_factory',
|
|
self.__class__.Comparator)
|
|
self.descriptor = kwargs.pop('descriptor', None)
|
|
self.extension = kwargs.pop('extension', None)
|
|
self.active_history = kwargs.pop('active_history', False)
|
|
self.expire_on_flush = kwargs.pop('expire_on_flush', True)
|
|
|
|
if 'info' in kwargs:
|
|
self.info = kwargs.pop('info')
|
|
|
|
if 'doc' in kwargs:
|
|
self.doc = kwargs.pop('doc')
|
|
else:
|
|
for col in reversed(self.columns):
|
|
doc = getattr(col, 'doc', None)
|
|
if doc is not None:
|
|
self.doc = doc
|
|
break
|
|
else:
|
|
self.doc = None
|
|
|
|
if kwargs:
|
|
raise TypeError(
|
|
"%s received unexpected keyword argument(s): %s" % (
|
|
self.__class__.__name__,
|
|
', '.join(sorted(kwargs.keys()))))
|
|
|
|
util.set_creation_order(self)
|
|
|
|
self.strategy_key = (
|
|
("deferred", self.deferred),
|
|
("instrument", self.instrument)
|
|
)
|
|
|
|
@util.dependencies("sqlalchemy.orm.state", "sqlalchemy.orm.strategies")
|
|
def _memoized_attr__deferred_column_loader(self, state, strategies):
|
|
return state.InstanceState._instance_level_callable_processor(
|
|
self.parent.class_manager,
|
|
strategies.LoadDeferredColumns(self.key), self.key)
|
|
|
|
@property
|
|
def expression(self):
|
|
"""Return the primary column or expression for this ColumnProperty.
|
|
|
|
"""
|
|
return self.columns[0]
|
|
|
|
def instrument_class(self, mapper):
|
|
if not self.instrument:
|
|
return
|
|
|
|
attributes.register_descriptor(
|
|
mapper.class_,
|
|
self.key,
|
|
comparator=self.comparator_factory(self, mapper),
|
|
parententity=mapper,
|
|
doc=self.doc
|
|
)
|
|
|
|
def do_init(self):
|
|
super(ColumnProperty, self).do_init()
|
|
if len(self.columns) > 1 and \
|
|
set(self.parent.primary_key).issuperset(self.columns):
|
|
util.warn(
|
|
("On mapper %s, primary key column '%s' is being combined "
|
|
"with distinct primary key column '%s' in attribute '%s'. "
|
|
"Use explicit properties to give each column its own mapped "
|
|
"attribute name.") % (self.parent, self.columns[1],
|
|
self.columns[0], self.key))
|
|
|
|
def copy(self):
|
|
return ColumnProperty(
|
|
deferred=self.deferred,
|
|
group=self.group,
|
|
active_history=self.active_history,
|
|
*self.columns)
|
|
|
|
def _getcommitted(self, state, dict_, column,
|
|
passive=attributes.PASSIVE_OFF):
|
|
return state.get_impl(self.key).\
|
|
get_committed_value(state, dict_, passive=passive)
|
|
|
|
def merge(self, session, source_state, source_dict, dest_state,
|
|
dest_dict, load, _recursive, _resolve_conflict_map):
|
|
if not self.instrument:
|
|
return
|
|
elif self.key in source_dict:
|
|
value = source_dict[self.key]
|
|
|
|
if not load:
|
|
dest_dict[self.key] = value
|
|
else:
|
|
impl = dest_state.get_impl(self.key)
|
|
impl.set(dest_state, dest_dict, value, None)
|
|
elif dest_state.has_identity and self.key not in dest_dict:
|
|
dest_state._expire_attributes(
|
|
dest_dict, [self.key], no_loader=True)
|
|
|
|
class Comparator(util.MemoizedSlots, PropComparator):
|
|
"""Produce boolean, comparison, and other operators for
|
|
:class:`.ColumnProperty` attributes.
|
|
|
|
See the documentation for :class:`.PropComparator` for a brief
|
|
overview.
|
|
|
|
See also:
|
|
|
|
:class:`.PropComparator`
|
|
|
|
:class:`.ColumnOperators`
|
|
|
|
:ref:`types_operators`
|
|
|
|
:attr:`.TypeEngine.comparator_factory`
|
|
|
|
"""
|
|
|
|
__slots__ = '__clause_element__', 'info'
|
|
|
|
def _memoized_method___clause_element__(self):
|
|
if self.adapter:
|
|
return self.adapter(self.prop.columns[0])
|
|
else:
|
|
# no adapter, so we aren't aliased
|
|
# assert self._parententity is self._parentmapper
|
|
return self.prop.columns[0]._annotate({
|
|
"parententity": self._parententity,
|
|
"parentmapper": self._parententity})
|
|
|
|
def _memoized_attr_info(self):
|
|
ce = self.__clause_element__()
|
|
try:
|
|
return ce.info
|
|
except AttributeError:
|
|
return self.prop.info
|
|
|
|
def _fallback_getattr(self, key):
|
|
"""proxy attribute access down to the mapped column.
|
|
|
|
this allows user-defined comparison methods to be accessed.
|
|
"""
|
|
return getattr(self.__clause_element__(), key)
|
|
|
|
def operate(self, op, *other, **kwargs):
|
|
return op(self.__clause_element__(), *other, **kwargs)
|
|
|
|
def reverse_operate(self, op, other, **kwargs):
|
|
col = self.__clause_element__()
|
|
return op(col._bind_param(op, other), col, **kwargs)
|
|
|
|
def __str__(self):
|
|
return str(self.parent.class_.__name__) + "." + self.key
|