JezK
Edit File: annotation.py
# sql/annotation.py # Copyright (C) 2005-2024 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 """The :class:`.Annotated` class and related routines; creates hash-equivalent copies of SQL constructs which contain context-specific markers and associations. """ from . import operators from .base import HasCacheKey from .traversals import anon_map from .visitors import InternalTraversal from .. import util EMPTY_ANNOTATIONS = util.immutabledict() class SupportsAnnotations(object): _annotations = EMPTY_ANNOTATIONS @util.memoized_property def _annotations_cache_key(self): anon_map_ = anon_map() return self._gen_annotations_cache_key(anon_map_) def _gen_annotations_cache_key(self, anon_map): return ( "_annotations", tuple( ( key, value._gen_cache_key(anon_map, []) if isinstance(value, HasCacheKey) else value, ) for key, value in [ (key, self._annotations[key]) for key in sorted(self._annotations) ] ), ) class SupportsCloneAnnotations(SupportsAnnotations): _clone_annotations_traverse_internals = [ ("_annotations", InternalTraversal.dp_annotations_key) ] def _annotate(self, values): """return a copy of this ClauseElement with annotations updated by the given dictionary. """ new = self._clone() new._annotations = new._annotations.union(values) new.__dict__.pop("_annotations_cache_key", None) new.__dict__.pop("_generate_cache_key", None) return new def _with_annotations(self, values): """return a copy of this ClauseElement with annotations replaced by the given dictionary. """ new = self._clone() new._annotations = util.immutabledict(values) new.__dict__.pop("_annotations_cache_key", None) new.__dict__.pop("_generate_cache_key", None) return new def _deannotate(self, values=None, clone=False): """return a copy of this :class:`_expression.ClauseElement` with annotations removed. :param values: optional tuple of individual values to remove. """ if clone or self._annotations: # clone is used when we are also copying # the expression for a deep deannotation new = self._clone() new._annotations = util.immutabledict() new.__dict__.pop("_annotations_cache_key", None) return new else: return self class SupportsWrappingAnnotations(SupportsAnnotations): def _annotate(self, values): """return a copy of this ClauseElement with annotations updated by the given dictionary. """ return Annotated(self, values) def _with_annotations(self, values): """return a copy of this ClauseElement with annotations replaced by the given dictionary. """ return Annotated(self, values) def _deannotate(self, values=None, clone=False): """return a copy of this :class:`_expression.ClauseElement` with annotations removed. :param values: optional tuple of individual values to remove. """ if clone: s = self._clone() return s else: return self class Annotated(object): """clones a SupportsAnnotated 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. .. note:: The rationale for Annotated producing a brand new class, rather than placing the functionality directly within ClauseElement, is **performance**. The __hash__() method is absent on plain ClauseElement which leads to significantly reduced function call overhead, as the use of sets and dictionaries against ClauseElement objects is prevalent, but most are not "annotated". """ _is_column_operators = False 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.__dict__.pop("_annotations_cache_key", None) self.__dict__.pop("_generate_cache_key", None) self.__element = element self._annotations = util.immutabledict(values) self._hash = hash(element) def _annotate(self, values): _values = self._annotations.union(values) return self._with_annotations(_values) def _with_annotations(self, values): clone = self.__class__.__new__(self.__class__) clone.__dict__ = self.__dict__.copy() clone.__dict__.pop("_annotations_cache_key", None) clone.__dict__.pop("_generate_cache_key", None) clone._annotations = values return clone def _deannotate(self, values=None, clone=True): if values is None: return self.__element else: return self._with_annotations( util.immutabledict( { key: value for key, value in self._annotations.items() if key not in 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, **kw): clone = self.__element._clone(**kw) 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 __reduce__(self): return self.__class__, (self.__element, self._annotations) def __hash__(self): return self._hash def __eq__(self, other): if self._is_column_operators: return self.__element.__class__.__eq__(self, other) else: return hash(other) == hash(self) @property def entity_namespace(self): if "entity_namespace" in self._annotations: return self._annotations["entity_namespace"].entity_namespace else: return self.__element.entity_namespace # 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; additionally, other # decisions can be made up front about the type of object being annotated # just once per class rather than per-instance. annotated_classes = {} def _safe_annotate(to_annotate, annotations): try: _annotate = to_annotate._annotate except AttributeError: # skip objects that don't actually have an `_annotate` # attribute, namely QueryableAttribute inside of a join # condition return to_annotate else: return _annotate(annotations) def _deep_annotate( element, annotations, exclude=None, detect_subquery_cols=False ): """Deep copy the given ClauseElement, annotating each element with the given annotations dictionary. Elements within the exclude collection will be cloned but not annotated. """ # annotated objects hack the __hash__() method so if we want to # uniquely process them we have to use id() cloned_ids = {} def clone(elem, **kw): kw["detect_subquery_cols"] = detect_subquery_cols id_ = id(elem) if id_ in cloned_ids: return cloned_ids[id_] if ( exclude and hasattr(elem, "proxy_set") and elem.proxy_set.intersection(exclude) ): newelem = elem._clone(clone=clone, **kw) elif annotations != elem._annotations: if detect_subquery_cols and elem._is_immutable: newelem = _safe_annotate( elem._clone(clone=clone, **kw), annotations ) else: newelem = _safe_annotate(elem, annotations) else: newelem = elem newelem._copy_internals(clone=clone) cloned_ids[id_] = newelem return newelem if element is not None: element = clone(element) clone = None # remove gc cycles return element def _deep_deannotate(element, values=None): """Deep copy the given element, removing annotations.""" cloned = {} def clone(elem, **kw): if values: key = id(elem) else: key = elem if key not in cloned: newelem = elem._deannotate(values=values, clone=True) newelem._copy_internals(clone=clone) cloned[key] = newelem return newelem else: return cloned[key] if element is not None: element = clone(element) clone = None # remove gc cycles 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 "don't 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 if "_traverse_internals" in cls.__dict__: anno_cls._traverse_internals = list(cls._traverse_internals) + [ ("_annotations", InternalTraversal.dp_annotations_key) ] elif cls.__dict__.get("inherit_cache", False): anno_cls._traverse_internals = list(cls._traverse_internals) + [ ("_annotations", InternalTraversal.dp_annotations_key) ] # some classes include this even if they have traverse_internals # e.g. BindParameter, add it if present. if cls.__dict__.get("inherit_cache", False): anno_cls.inherit_cache = True anno_cls._is_column_operators = issubclass(cls, operators.ColumnOperators) return anno_cls def _prepare_annotations(target_hierarchy, base_cls): for cls in util.walk_subclasses(target_hierarchy): _new_annotation_type(cls, base_cls)