352 lines
12 KiB
Python
352 lines
12 KiB
Python
"""
|
|
Various data structures used in query construction.
|
|
|
|
Factored out from django.db.models.query to avoid making the main module very
|
|
large and/or so that they can be used by other modules without getting into
|
|
circular import difficulties.
|
|
"""
|
|
import copy
|
|
import functools
|
|
import inspect
|
|
import warnings
|
|
from collections import namedtuple
|
|
|
|
from django.core.exceptions import FieldDoesNotExist, FieldError
|
|
from django.db.models.constants import LOOKUP_SEP
|
|
from django.utils import tree
|
|
from django.utils.deprecation import RemovedInDjango40Warning
|
|
|
|
# PathInfo is used when converting lookups (fk__somecol). The contents
|
|
# describe the relation in Model terms (model Options and Fields for both
|
|
# sides of the relation. The join_field is the field backing the relation.
|
|
PathInfo = namedtuple('PathInfo', 'from_opts to_opts target_fields join_field m2m direct filtered_relation')
|
|
|
|
|
|
class InvalidQueryType(type):
|
|
@property
|
|
def _subclasses(self):
|
|
return (FieldDoesNotExist, FieldError)
|
|
|
|
def __warn(self):
|
|
warnings.warn(
|
|
'The InvalidQuery exception class is deprecated. Use '
|
|
'FieldDoesNotExist or FieldError instead.',
|
|
category=RemovedInDjango40Warning,
|
|
stacklevel=4,
|
|
)
|
|
|
|
def __instancecheck__(self, instance):
|
|
self.__warn()
|
|
return isinstance(instance, self._subclasses) or super().__instancecheck__(instance)
|
|
|
|
def __subclasscheck__(self, subclass):
|
|
self.__warn()
|
|
return issubclass(subclass, self._subclasses) or super().__subclasscheck__(subclass)
|
|
|
|
|
|
class InvalidQuery(Exception, metaclass=InvalidQueryType):
|
|
pass
|
|
|
|
|
|
def subclasses(cls):
|
|
yield cls
|
|
for subclass in cls.__subclasses__():
|
|
yield from subclasses(subclass)
|
|
|
|
|
|
class Q(tree.Node):
|
|
"""
|
|
Encapsulate filters as objects that can then be combined logically (using
|
|
`&` and `|`).
|
|
"""
|
|
# Connection types
|
|
AND = 'AND'
|
|
OR = 'OR'
|
|
default = AND
|
|
conditional = True
|
|
|
|
def __init__(self, *args, _connector=None, _negated=False, **kwargs):
|
|
super().__init__(children=[*args, *sorted(kwargs.items())], connector=_connector, negated=_negated)
|
|
|
|
def _combine(self, other, conn):
|
|
if not isinstance(other, Q):
|
|
raise TypeError(other)
|
|
|
|
# If the other Q() is empty, ignore it and just use `self`.
|
|
if not other:
|
|
return copy.deepcopy(self)
|
|
# Or if this Q is empty, ignore it and just use `other`.
|
|
elif not self:
|
|
return copy.deepcopy(other)
|
|
|
|
obj = type(self)()
|
|
obj.connector = conn
|
|
obj.add(self, conn)
|
|
obj.add(other, conn)
|
|
return obj
|
|
|
|
def __or__(self, other):
|
|
return self._combine(other, self.OR)
|
|
|
|
def __and__(self, other):
|
|
return self._combine(other, self.AND)
|
|
|
|
def __invert__(self):
|
|
obj = type(self)()
|
|
obj.add(self, self.AND)
|
|
obj.negate()
|
|
return obj
|
|
|
|
def resolve_expression(self, query=None, allow_joins=True, reuse=None, summarize=False, for_save=False):
|
|
# We must promote any new joins to left outer joins so that when Q is
|
|
# used as an expression, rows aren't filtered due to joins.
|
|
clause, joins = query._add_q(
|
|
self, reuse, allow_joins=allow_joins, split_subq=False,
|
|
check_filterable=False,
|
|
)
|
|
query.promote_joins(joins)
|
|
return clause
|
|
|
|
def deconstruct(self):
|
|
path = '%s.%s' % (self.__class__.__module__, self.__class__.__name__)
|
|
if path.startswith('django.db.models.query_utils'):
|
|
path = path.replace('django.db.models.query_utils', 'django.db.models')
|
|
args, kwargs = (), {}
|
|
if len(self.children) == 1 and not isinstance(self.children[0], Q):
|
|
child = self.children[0]
|
|
kwargs = {child[0]: child[1]}
|
|
else:
|
|
args = tuple(self.children)
|
|
if self.connector != self.default:
|
|
kwargs = {'_connector': self.connector}
|
|
if self.negated:
|
|
kwargs['_negated'] = True
|
|
return path, args, kwargs
|
|
|
|
|
|
class DeferredAttribute:
|
|
"""
|
|
A wrapper for a deferred-loading field. When the value is read from this
|
|
object the first time, the query is executed.
|
|
"""
|
|
def __init__(self, field):
|
|
self.field = field
|
|
|
|
def __get__(self, instance, cls=None):
|
|
"""
|
|
Retrieve and caches the value from the datastore on the first lookup.
|
|
Return the cached value.
|
|
"""
|
|
if instance is None:
|
|
return self
|
|
data = instance.__dict__
|
|
field_name = self.field.attname
|
|
if data.get(field_name, self) is self:
|
|
# Let's see if the field is part of the parent chain. If so we
|
|
# might be able to reuse the already loaded value. Refs #18343.
|
|
val = self._check_parent_chain(instance)
|
|
if val is None:
|
|
instance.refresh_from_db(fields=[field_name])
|
|
val = getattr(instance, field_name)
|
|
data[field_name] = val
|
|
return data[field_name]
|
|
|
|
def _check_parent_chain(self, instance):
|
|
"""
|
|
Check if the field value can be fetched from a parent field already
|
|
loaded in the instance. This can be done if the to-be fetched
|
|
field is a primary key field.
|
|
"""
|
|
opts = instance._meta
|
|
link_field = opts.get_ancestor_link(self.field.model)
|
|
if self.field.primary_key and self.field != link_field:
|
|
return getattr(instance, link_field.attname)
|
|
return None
|
|
|
|
|
|
class RegisterLookupMixin:
|
|
|
|
@classmethod
|
|
def _get_lookup(cls, lookup_name):
|
|
return cls.get_lookups().get(lookup_name, None)
|
|
|
|
@classmethod
|
|
@functools.lru_cache(maxsize=None)
|
|
def get_lookups(cls):
|
|
class_lookups = [parent.__dict__.get('class_lookups', {}) for parent in inspect.getmro(cls)]
|
|
return cls.merge_dicts(class_lookups)
|
|
|
|
def get_lookup(self, lookup_name):
|
|
from django.db.models.lookups import Lookup
|
|
found = self._get_lookup(lookup_name)
|
|
if found is None and hasattr(self, 'output_field'):
|
|
return self.output_field.get_lookup(lookup_name)
|
|
if found is not None and not issubclass(found, Lookup):
|
|
return None
|
|
return found
|
|
|
|
def get_transform(self, lookup_name):
|
|
from django.db.models.lookups import Transform
|
|
found = self._get_lookup(lookup_name)
|
|
if found is None and hasattr(self, 'output_field'):
|
|
return self.output_field.get_transform(lookup_name)
|
|
if found is not None and not issubclass(found, Transform):
|
|
return None
|
|
return found
|
|
|
|
@staticmethod
|
|
def merge_dicts(dicts):
|
|
"""
|
|
Merge dicts in reverse to preference the order of the original list. e.g.,
|
|
merge_dicts([a, b]) will preference the keys in 'a' over those in 'b'.
|
|
"""
|
|
merged = {}
|
|
for d in reversed(dicts):
|
|
merged.update(d)
|
|
return merged
|
|
|
|
@classmethod
|
|
def _clear_cached_lookups(cls):
|
|
for subclass in subclasses(cls):
|
|
subclass.get_lookups.cache_clear()
|
|
|
|
@classmethod
|
|
def register_lookup(cls, lookup, lookup_name=None):
|
|
if lookup_name is None:
|
|
lookup_name = lookup.lookup_name
|
|
if 'class_lookups' not in cls.__dict__:
|
|
cls.class_lookups = {}
|
|
cls.class_lookups[lookup_name] = lookup
|
|
cls._clear_cached_lookups()
|
|
return lookup
|
|
|
|
@classmethod
|
|
def _unregister_lookup(cls, lookup, lookup_name=None):
|
|
"""
|
|
Remove given lookup from cls lookups. For use in tests only as it's
|
|
not thread-safe.
|
|
"""
|
|
if lookup_name is None:
|
|
lookup_name = lookup.lookup_name
|
|
del cls.class_lookups[lookup_name]
|
|
|
|
|
|
def select_related_descend(field, restricted, requested, load_fields, reverse=False):
|
|
"""
|
|
Return True if this field should be used to descend deeper for
|
|
select_related() purposes. Used by both the query construction code
|
|
(sql.query.fill_related_selections()) and the model instance creation code
|
|
(query.get_klass_info()).
|
|
|
|
Arguments:
|
|
* field - the field to be checked
|
|
* restricted - a boolean field, indicating if the field list has been
|
|
manually restricted using a requested clause)
|
|
* requested - The select_related() dictionary.
|
|
* load_fields - the set of fields to be loaded on this model
|
|
* reverse - boolean, True if we are checking a reverse select related
|
|
"""
|
|
if not field.remote_field:
|
|
return False
|
|
if field.remote_field.parent_link and not reverse:
|
|
return False
|
|
if restricted:
|
|
if reverse and field.related_query_name() not in requested:
|
|
return False
|
|
if not reverse and field.name not in requested:
|
|
return False
|
|
if not restricted and field.null:
|
|
return False
|
|
if load_fields:
|
|
if field.attname not in load_fields:
|
|
if restricted and field.name in requested:
|
|
msg = (
|
|
'Field %s.%s cannot be both deferred and traversed using '
|
|
'select_related at the same time.'
|
|
) % (field.model._meta.object_name, field.name)
|
|
raise FieldError(msg)
|
|
return True
|
|
|
|
|
|
def refs_expression(lookup_parts, annotations):
|
|
"""
|
|
Check if the lookup_parts contains references to the given annotations set.
|
|
Because the LOOKUP_SEP is contained in the default annotation names, check
|
|
each prefix of the lookup_parts for a match.
|
|
"""
|
|
for n in range(1, len(lookup_parts) + 1):
|
|
level_n_lookup = LOOKUP_SEP.join(lookup_parts[0:n])
|
|
if level_n_lookup in annotations and annotations[level_n_lookup]:
|
|
return annotations[level_n_lookup], lookup_parts[n:]
|
|
return False, ()
|
|
|
|
|
|
def check_rel_lookup_compatibility(model, target_opts, field):
|
|
"""
|
|
Check that self.model is compatible with target_opts. Compatibility
|
|
is OK if:
|
|
1) model and opts match (where proxy inheritance is removed)
|
|
2) model is parent of opts' model or the other way around
|
|
"""
|
|
def check(opts):
|
|
return (
|
|
model._meta.concrete_model == opts.concrete_model or
|
|
opts.concrete_model in model._meta.get_parent_list() or
|
|
model in opts.get_parent_list()
|
|
)
|
|
# If the field is a primary key, then doing a query against the field's
|
|
# model is ok, too. Consider the case:
|
|
# class Restaurant(models.Model):
|
|
# place = OneToOneField(Place, primary_key=True):
|
|
# Restaurant.objects.filter(pk__in=Restaurant.objects.all()).
|
|
# If we didn't have the primary key check, then pk__in (== place__in) would
|
|
# give Place's opts as the target opts, but Restaurant isn't compatible
|
|
# with that. This logic applies only to primary keys, as when doing __in=qs,
|
|
# we are going to turn this into __in=qs.values('pk') later on.
|
|
return (
|
|
check(target_opts) or
|
|
(getattr(field, 'primary_key', False) and check(field.model._meta))
|
|
)
|
|
|
|
|
|
class FilteredRelation:
|
|
"""Specify custom filtering in the ON clause of SQL joins."""
|
|
|
|
def __init__(self, relation_name, *, condition=Q()):
|
|
if not relation_name:
|
|
raise ValueError('relation_name cannot be empty.')
|
|
self.relation_name = relation_name
|
|
self.alias = None
|
|
if not isinstance(condition, Q):
|
|
raise ValueError('condition argument must be a Q() instance.')
|
|
self.condition = condition
|
|
self.path = []
|
|
|
|
def __eq__(self, other):
|
|
if not isinstance(other, self.__class__):
|
|
return NotImplemented
|
|
return (
|
|
self.relation_name == other.relation_name and
|
|
self.alias == other.alias and
|
|
self.condition == other.condition
|
|
)
|
|
|
|
def clone(self):
|
|
clone = FilteredRelation(self.relation_name, condition=self.condition)
|
|
clone.alias = self.alias
|
|
clone.path = self.path[:]
|
|
return clone
|
|
|
|
def resolve_expression(self, *args, **kwargs):
|
|
"""
|
|
QuerySet.annotate() only accepts expression-like arguments
|
|
(with a resolve_expression() method).
|
|
"""
|
|
raise NotImplementedError('FilteredRelation.resolve_expression() is unused.')
|
|
|
|
def as_sql(self, compiler, connection):
|
|
# Resolve the condition in Join.filtered_relation.
|
|
query = compiler.query
|
|
where = query.build_filtered_relation_q(self.condition, reuse=set(self.path))
|
|
return compiler.compile(where)
|