AlkantarClanX12
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# orm/path_registry.py
# Copyright (C) 2005-2021 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
"""Path tracking utilities, representing mapper graph traversals.
"""
from itertools import chain
import logging
from .base import class_mapper
from .. import exc
from .. import inspection
from .. import util
log = logging.getLogger(__name__)
def _unreduce_path(path):
return PathRegistry.deserialize(path)
_WILDCARD_TOKEN = "*"
_DEFAULT_TOKEN = "_sa_default"
class PathRegistry(object):
"""Represent query load paths and registry functions.
Basically represents structures like:
(<User mapper>, "orders", <Order mapper>, "items", <Item mapper>)
These structures are generated by things like
query options (joinedload(), subqueryload(), etc.) and are
used to compose keys stored in the query._attributes dictionary
for various options.
They are then re-composed at query compile/result row time as
the query is formed and as rows are fetched, where they again
serve to compose keys to look up options in the context.attributes
dictionary, which is copied from query._attributes.
The path structure has a limited amount of caching, where each
"root" ultimately pulls from a fixed registry associated with
the first mapper, that also contains elements for each of its
property keys. However paths longer than two elements, which
are the exception rather than the rule, are generated on an
as-needed basis.
"""
__slots__ = ()
is_token = False
is_root = False
def __eq__(self, other):
try:
return other is not None and self.path == other.path
except AttributeError:
util.warn(
"Comparison of PathRegistry to %r is not supported"
% (type(other))
)
return False
def __ne__(self, other):
try:
return other is None or self.path != other.path
except AttributeError:
util.warn(
"Comparison of PathRegistry to %r is not supported"
% (type(other))
)
return True
def set(self, attributes, key, value):
log.debug("set '%s' on path '%s' to '%s'", key, self, value)
attributes[(key, self.natural_path)] = value
def setdefault(self, attributes, key, value):
log.debug("setdefault '%s' on path '%s' to '%s'", key, self, value)
attributes.setdefault((key, self.natural_path), value)
def get(self, attributes, key, value=None):
key = (key, self.natural_path)
if key in attributes:
return attributes[key]
else:
return value
def __len__(self):
return len(self.path)
@property
def length(self):
return len(self.path)
def pairs(self):
path = self.path
for i in range(0, len(path), 2):
yield path[i], path[i + 1]
def contains_mapper(self, mapper):
for path_mapper in [self.path[i] for i in range(0, len(self.path), 2)]:
if path_mapper.is_mapper and path_mapper.isa(mapper):
return True
else:
return False
def contains(self, attributes, key):
return (key, self.path) in attributes
def __reduce__(self):
return _unreduce_path, (self.serialize(),)
@classmethod
def _serialize_path(cls, path):
return list(
zip(
[m.class_ for m in [path[i] for i in range(0, len(path), 2)]],
[path[i].key for i in range(1, len(path), 2)] + [None],
)
)
@classmethod
def _deserialize_path(cls, path):
p = tuple(
chain(
*[
(
class_mapper(mcls),
class_mapper(mcls).attrs[key]
if key is not None
else None,
)
for mcls, key in path
]
)
)
if p and p[-1] is None:
p = p[0:-1]
return p
@classmethod
def serialize_context_dict(cls, dict_, tokens):
return [
((key, cls._serialize_path(path)), value)
for (key, path), value in [
(k, v)
for k, v in dict_.items()
if isinstance(k, tuple) and k[0] in tokens
]
]
@classmethod
def deserialize_context_dict(cls, serialized):
return util.OrderedDict(
((key, tuple(cls._deserialize_path(path))), value)
for (key, path), value in serialized
)
def serialize(self):
path = self.path
return self._serialize_path(path)
@classmethod
def deserialize(cls, path):
if path is None:
return None
p = cls._deserialize_path(path)
return cls.coerce(p)
@classmethod
def per_mapper(cls, mapper):
if mapper.is_mapper:
return CachingEntityRegistry(cls.root, mapper)
else:
return SlotsEntityRegistry(cls.root, mapper)
@classmethod
def coerce(cls, raw):
return util.reduce(lambda prev, next: prev[next], raw, cls.root)
def token(self, token):
if token.endswith(":" + _WILDCARD_TOKEN):
return TokenRegistry(self, token)
elif token.endswith(":" + _DEFAULT_TOKEN):
return TokenRegistry(self.root, token)
else:
raise exc.ArgumentError("invalid token: %s" % token)
def __add__(self, other):
return util.reduce(lambda prev, next: prev[next], other.path, self)
def __repr__(self):
return "%s(%r)" % (self.__class__.__name__, self.path)
class RootRegistry(PathRegistry):
"""Root registry, defers to mappers so that
paths are maintained per-root-mapper.
"""
path = natural_path = ()
has_entity = False
is_aliased_class = False
is_root = True
def __getitem__(self, entity):
return entity._path_registry
PathRegistry.root = RootRegistry()
class TokenRegistry(PathRegistry):
__slots__ = ("token", "parent", "path", "natural_path")
def __init__(self, parent, token):
self.token = token
self.parent = parent
self.path = parent.path + (token,)
self.natural_path = parent.natural_path + (token,)
has_entity = False
is_token = True
def generate_for_superclasses(self):
if not self.parent.is_aliased_class and not self.parent.is_root:
for ent in self.parent.mapper.iterate_to_root():
yield TokenRegistry(self.parent.parent[ent], self.token)
elif (
self.parent.is_aliased_class
and self.parent.entity._is_with_polymorphic
):
yield self
for ent in self.parent.entity._with_polymorphic_entities:
yield TokenRegistry(self.parent.parent[ent], self.token)
else:
yield self
def __getitem__(self, entity):
raise NotImplementedError()
class PropRegistry(PathRegistry):
is_unnatural = False
def __init__(self, parent, prop):
# restate this path in terms of the
# given MapperProperty's parent.
insp = inspection.inspect(parent[-1])
natural_parent = parent
if not insp.is_aliased_class or insp._use_mapper_path:
parent = natural_parent = parent.parent[prop.parent]
elif (
insp.is_aliased_class
and insp.with_polymorphic_mappers
and prop.parent in insp.with_polymorphic_mappers
):
subclass_entity = parent[-1]._entity_for_mapper(prop.parent)
parent = parent.parent[subclass_entity]
# when building a path where with_polymorphic() is in use,
# special logic to determine the "natural path" when subclass
# entities are used.
#
# here we are trying to distinguish between a path that starts
# on a the with_polymorhpic entity vs. one that starts on a
# normal entity that introduces a with_polymorphic() in the
# middle using of_type():
#
# # as in test_polymorphic_rel->
# # test_subqueryload_on_subclass_uses_path_correctly
# wp = with_polymorphic(RegularEntity, "*")
# sess.query(wp).options(someload(wp.SomeSubEntity.foos))
#
# vs
#
# # as in test_relationship->JoinedloadWPolyOfTypeContinued
# wp = with_polymorphic(SomeFoo, "*")
# sess.query(RegularEntity).options(
# someload(RegularEntity.foos.of_type(wp))
# .someload(wp.SubFoo.bar)
# )
#
# in the former case, the Query as it generates a path that we
# want to match will be in terms of the with_polymorphic at the
# beginning. in the latter case, Query will generate simple
# paths that don't know about this with_polymorphic, so we must
# use a separate natural path.
#
#
if parent.parent:
natural_parent = parent.parent[subclass_entity.mapper]
self.is_unnatural = True
else:
natural_parent = parent
elif (
natural_parent.parent
and insp.is_aliased_class
and prop.parent # this should always be the case here
is not insp.mapper
and insp.mapper.isa(prop.parent)
):
natural_parent = parent.parent[prop.parent]
self.prop = prop
self.parent = parent
self.path = parent.path + (prop,)
self.natural_path = natural_parent.natural_path + (prop,)
self._wildcard_path_loader_key = (
"loader",
parent.path + self.prop._wildcard_token,
)
self._default_path_loader_key = self.prop._default_path_loader_key
self._loader_key = ("loader", self.path)
def __str__(self):
return " -> ".join(str(elem) for elem in self.path)
@util.memoized_property
def has_entity(self):
return hasattr(self.prop, "mapper")
@util.memoized_property
def entity(self):
return self.prop.mapper
@property
def mapper(self):
return self.entity
@property
def entity_path(self):
return self[self.entity]
def __getitem__(self, entity):
if isinstance(entity, (int, slice)):
return self.path[entity]
else:
return SlotsEntityRegistry(self, entity)
class AbstractEntityRegistry(PathRegistry):
__slots__ = ()
has_entity = True
def __init__(self, parent, entity):
self.key = entity
self.parent = parent
self.is_aliased_class = entity.is_aliased_class
self.entity = entity
self.path = parent.path + (entity,)
# the "natural path" is the path that we get when Query is traversing
# from the lead entities into the various relationships; it corresponds
# to the structure of mappers and relationships. when we are given a
# path that comes from loader options, as of 1.3 it can have ac-hoc
# with_polymorphic() and other AliasedInsp objects inside of it, which
# are usually not present in mappings. So here we track both the
# "enhanced" path in self.path and the "natural" path that doesn't
# include those objects so these two traversals can be matched up.
# the test here for "(self.is_aliased_class or parent.is_unnatural)"
# are to avoid the more expensive conditional logic that follows if we
# know we don't have to do it. This conditional can just as well be
# "if parent.path:", it just is more function calls.
if parent.path and (self.is_aliased_class or parent.is_unnatural):
# this is an infrequent code path used only for loader strategies
# that also make use of of_type().
if entity.mapper.isa(parent.natural_path[-1].entity):
self.natural_path = parent.natural_path + (entity.mapper,)
else:
self.natural_path = parent.natural_path + (
parent.natural_path[-1].entity,
)
else:
self.natural_path = self.path
@property
def entity_path(self):
return self
@property
def mapper(self):
return inspection.inspect(self.entity).mapper
def __bool__(self):
return True
__nonzero__ = __bool__
def __getitem__(self, entity):
if isinstance(entity, (int, slice)):
return self.path[entity]
else:
return PropRegistry(self, entity)
class SlotsEntityRegistry(AbstractEntityRegistry):
# for aliased class, return lightweight, no-cycles created
# version
__slots__ = (
"key",
"parent",
"is_aliased_class",
"entity",
"path",
"natural_path",
)
class CachingEntityRegistry(AbstractEntityRegistry, dict):
# for long lived mapper, return dict based caching
# version that creates reference cycles
def __getitem__(self, entity):
if isinstance(entity, (int, slice)):
return self.path[entity]
else:
return dict.__getitem__(self, entity)
def __missing__(self, key):
self[key] = item = PropRegistry(self, key)
return item