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|
# sql/annotation.py
# Copyright (C) 2005-2016 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
"""The :class:`.Annotated` class and related routines; creates hash-equivalent
copies of SQL constructs which contain context-specific markers and
associations.
"""
from .. import util
from . import operators
class Annotated(object):
"""clones a ClauseElement and applies an 'annotations' dictionary.
Unlike regular clones, this clone also mimics __hash__() and
__cmp__() of the original element so that it takes its place
in hashed collections.
A reference to the original element is maintained, for the important
reason of keeping its hash value current. When GC'ed, the
hash value may be reused, causing conflicts.
"""
def __new__(cls, *args):
if not args:
# clone constructor
return object.__new__(cls)
else:
element, values = args
# pull appropriate subclass from registry of annotated
# classes
try:
cls = annotated_classes[element.__class__]
except KeyError:
cls = _new_annotation_type(element.__class__, cls)
return object.__new__(cls)
def __init__(self, element, values):
self.__dict__ = element.__dict__.copy()
self.__element = element
self._annotations = values
self._hash = hash(element)
def _annotate(self, values):
_values = self._annotations.copy()
_values.update(values)
return self._with_annotations(_values)
def _with_annotations(self, values):
clone = self.__class__.__new__(self.__class__)
clone.__dict__ = self.__dict__.copy()
clone._annotations = values
return clone
def _deannotate(self, values=None, clone=True):
if values is None:
return self.__element
else:
_values = self._annotations.copy()
for v in values:
_values.pop(v, None)
return self._with_annotations(_values)
def _compiler_dispatch(self, visitor, **kw):
return self.__element.__class__._compiler_dispatch(
self, visitor, **kw)
@property
def _constructor(self):
return self.__element._constructor
def _clone(self):
clone = self.__element._clone()
if clone is self.__element:
# detect immutable, don't change anything
return self
else:
# update the clone with any changes that have occurred
# to this object's __dict__.
clone.__dict__.update(self.__dict__)
return self.__class__(clone, self._annotations)
def __hash__(self):
return self._hash
def __eq__(self, other):
if isinstance(self.__element, operators.ColumnOperators):
return self.__element.__class__.__eq__(self, other)
else:
return hash(other) == hash(self)
# hard-generate Annotated subclasses. this technique
# is used instead of on-the-fly types (i.e. type.__new__())
# so that the resulting objects are pickleable.
annotated_classes = {}
def _deep_annotate(element, annotations, exclude=None):
"""Deep copy the given ClauseElement, annotating each element
with the given annotations dictionary.
Elements within the exclude collection will be cloned but not annotated.
"""
def clone(elem):
if exclude and \
hasattr(elem, 'proxy_set') and \
elem.proxy_set.intersection(exclude):
newelem = elem._clone()
elif annotations != elem._annotations:
newelem = elem._annotate(annotations)
else:
newelem = elem
newelem._copy_internals(clone=clone)
return newelem
if element is not None:
element = clone(element)
return element
def _deep_deannotate(element, values=None):
"""Deep copy the given element, removing annotations."""
cloned = util.column_dict()
def clone(elem):
# if a values dict is given,
# the elem must be cloned each time it appears,
# as there may be different annotations in source
# elements that are remaining. if totally
# removing all annotations, can assume the same
# slate...
if values or elem not in cloned:
newelem = elem._deannotate(values=values, clone=True)
newelem._copy_internals(clone=clone)
if not values:
cloned[elem] = newelem
return newelem
else:
return cloned[elem]
if element is not None:
element = clone(element)
return element
def _shallow_annotate(element, annotations):
"""Annotate the given ClauseElement and copy its internals so that
internal objects refer to the new annotated object.
Basically used to apply a "dont traverse" annotation to a
selectable, without digging throughout the whole
structure wasting time.
"""
element = element._annotate(annotations)
element._copy_internals()
return element
def _new_annotation_type(cls, base_cls):
if issubclass(cls, Annotated):
return cls
elif cls in annotated_classes:
return annotated_classes[cls]
for super_ in cls.__mro__:
# check if an Annotated subclass more specific than
# the given base_cls is already registered, such
# as AnnotatedColumnElement.
if super_ in annotated_classes:
base_cls = annotated_classes[super_]
break
annotated_classes[cls] = anno_cls = type(
"Annotated%s" % cls.__name__,
(base_cls, cls), {})
globals()["Annotated%s" % cls.__name__] = anno_cls
return anno_cls
def _prepare_annotations(target_hierarchy, base_cls):
stack = [target_hierarchy]
while stack:
cls = stack.pop()
stack.extend(cls.__subclasses__())
_new_annotation_type(cls, base_cls)
|
