text: """
  The main QuerySet implementation. This provides the public API for the ORM.
  """
  
  import copy
  import operator
  import warnings
  from itertools import chain
  
  import django
  from django.conf import settings
  from django.core import exceptions
  from django.db import (
      DJANGO_VERSION_PICKLE_KEY,
      IntegrityError,
      NotSupportedError,
      connections,
      router,
      transaction,
  )
  from django.db.models import AutoField, DateField, DateTimeField, sql
  from django.db.models.constants import LOOKUP_SEP
  from django.db.models.deletion import Collector
  from django.db.models.expressions import Case, Expression, F, Ref, Value, When
  from django.db.models.functions import Cast, Trunc
  from django.db.models.query_utils import FilteredRelation, Q
  from django.db.models.sql.constants import CURSOR, GET_ITERATOR_CHUNK_SIZE
  from django.db.models.utils import create_namedtuple_class, resolve_callables
  from django.utils import timezone
  from django.utils.functional import cached_property, partition
  
  # The maximum number of results to fetch in a get() query.
  MAX_GET_RESULTS = 21
  
  # The maximum number of items to display in a QuerySet.__repr__
  REPR_OUTPUT_SIZE = 20
  
  
  class BaseIterable:
      def __init__(
          self, queryset, chunked_fetch=False, chunk_size=GET_ITERATOR_CHUNK_SIZE
      ):
          self.queryset = queryset
          self.chunked_fetch = chunked_fetch
          self.chunk_size = chunk_size
  
  
  class ModelIterable(BaseIterable):
      """Iterable that yields a model instance for each row."""
  
      def __iter__(self):
          queryset = self.queryset
          db = queryset.db
          compiler = queryset.query.get_compiler(using=db)
          # Execute the query. This will also fill compiler.select, klass_info,
          # and annotations.
          results = compiler.execute_sql(
              chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size
          )
          select, klass_info, annotation_col_map = (
              compiler.select,
              compiler.klass_info,
              compiler.annotation_col_map,
          )
          model_cls = klass_info["model"]
          select_fields = klass_info["select_fields"]
          model_fields_start, model_fields_end = select_fields[0], select_fields[-1] + 1
          init_list = [
              f[0].target.attname for f in select[model_fields_start:model_fields_end]
          ]
          related_populators = get_related_populators(klass_info, select, db)
          known_related_objects = [
              (
                  field,
                  related_objs,
                  operator.attrgetter(
                      *[
                          field.attname
                          if from_field == "self"
                          else queryset.model._meta.get_field(from_field).attname
                          for from_field in field.from_fields
                      ]
                  ),
              )
              for field, related_objs in queryset._known_related_objects.items()
          ]
          for row in compiler.results_iter(results):
              obj = model_cls.from_db(
                  db, init_list, row[model_fields_start:model_fields_end]
              )
              for rel_populator in related_populators:
                  rel_populator.populate(row, obj)
              if annotation_col_map:
                  for attr_name, col_pos in annotation_col_map.items():
                      setattr(obj, attr_name, row[col_pos])
  
              # Add the known related objects to the model.
              for field, rel_objs, rel_getter in known_related_objects:
                  # Avoid overwriting objects loaded by, e.g., select_related().
                  if field.is_cached(obj):
                      continue
                  rel_obj_id = rel_getter(obj)
                  try:
                      rel_obj = rel_objs[rel_obj_id]
                  except KeyError:
                      pass  # May happen in qs1 | qs2 scenarios.
                  else:
                      setattr(obj, field.name, rel_obj)
  
              yield obj
  
  
  class ValuesIterable(BaseIterable):
      """
      Iterable returned by QuerySet.values() that yields a dict for each row.
      """
  
      def __iter__(self):
          queryset = self.queryset
          query = queryset.query
          compiler = query.get_compiler(queryset.db)
  
          # extra(select=...) cols are always at the start of the row.
          names = [
              *query.extra_select,
              *query.values_select,
              *query.annotation_select,
          ]
          indexes = range(len(names))
          for row in compiler.results_iter(
              chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size
          ):
              yield {names[i]: row[i] for i in indexes}
  
  
  class ValuesListIterable(BaseIterable):
      """
      Iterable returned by QuerySet.values_list(flat=False) that yields a tuple
      for each row.
      """
  
      def __iter__(self):
          queryset = self.queryset
          query = queryset.query
          compiler = query.get_compiler(queryset.db)
  
          if queryset._fields:
              # extra(select=...) cols are always at the start of the row.
              names = [
                  *query.extra_select,
                  *query.values_select,
                  *query.annotation_select,
              ]
              fields = [
                  *queryset._fields,
                  *(f for f in query.annotation_select if f not in queryset._fields),
              ]
              if fields != names:
                  # Reorder according to fields.
                  index_map = {name: idx for idx, name in enumerate(names)}
                  rowfactory = operator.itemgetter(*[index_map[f] for f in fields])
                  return map(
                      rowfactory,
                      compiler.results_iter(
                          chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size
                      ),
                  )
          return compiler.results_iter(
              tuple_expected=True,
              chunked_fetch=self.chunked_fetch,
              chunk_size=self.chunk_size,
          )
  
  
  class NamedValuesListIterable(ValuesListIterable):
      """
      Iterable returned by QuerySet.values_list(named=True) that yields a
      namedtuple for each row.
      """
  
      def __iter__(self):
          queryset = self.queryset
          if queryset._fields:
              names = queryset._fields
          else:
              query = queryset.query
              names = [
                  *query.extra_select,
                  *query.values_select,
                  *query.annotation_select,
              ]
          tuple_class = create_namedtuple_class(*names)
          new = tuple.__new__
          for row in super().__iter__():
              yield new(tuple_class, row)
  
  
  class FlatValuesListIterable(BaseIterable):
      """
      Iterable returned by QuerySet.values_list(flat=True) that yields single
      values.
      """
  
      def __iter__(self):
          queryset = self.queryset
          compiler = queryset.query.get_compiler(queryset.db)
          for row in compiler.results_iter(
              chunked_fetch=self.chunked_fetch, chunk_size=self.chunk_size
          ):
              yield row[0]
  
  
  class QuerySet:
      """Represent a lazy database lookup for a set of objects."""
  
      def __init__(self, model=None, query=None, using=None, hints=None):
          self.model = model
          self._db = using
          self._hints = hints or {}
          self._query = query or sql.Query(self.model)
          self._result_cache = None
          self._sticky_filter = False
          self._for_write = False
          self._prefetch_related_lookups = ()
          self._prefetch_done = False
          self._known_related_objects = {}  # {rel_field: {pk: rel_obj}}
          self._iterable_class = ModelIterable
          self._fields = None
          self._defer_next_filter = False
          self._deferred_filter = None
  
      @property
      def query(self):
          if self._deferred_filter:
              negate, args, kwargs = self._deferred_filter
              self._filter_or_exclude_inplace(negate, args, kwargs)
              self._deferred_filter = None
          return self._query
  
      @query.setter
      def query(self, value):
          if value.values_select:
              self._iterable_class = ValuesIterable
          self._query = value
  
      def as_manager(cls):
          # Address the circular dependency between `Queryset` and `Manager`.
          from django.db.models.manager import Manager
  
          manager = Manager.from_queryset(cls)()
          manager._built_with_as_manager = True
          return manager
  
      as_manager.queryset_only = True
      as_manager = classmethod(as_manager)
  
      ########################
      # PYTHON MAGIC METHODS #
      ########################
  
      def __deepcopy__(self, memo):
          """Don't populate the QuerySet's cache."""
          obj = self.__class__()
          for k, v in self.__dict__.items():
              if k == "_result_cache":
                  obj.__dict__[k] = None
              else:
                  obj.__dict__[k] = copy.deepcopy(v, memo)
          return obj
  
      def __getstate__(self):
          # Force the cache to be fully populated.
          self._fetch_all()
          return {**self.__dict__, DJANGO_VERSION_PICKLE_KEY: django.__version__}
  
      def __setstate__(self, state):
          pickled_version = state.get(DJANGO_VERSION_PICKLE_KEY)
          if pickled_version:
              if pickled_version != django.__version__:
                  warnings.warn(
                      "Pickled queryset instance's Django version %s does not "
                      "match the current version %s."
                      % (pickled_version, django.__version__),
                      RuntimeWarning,
                      stacklevel=2,
                  )
          else:
              warnings.warn(
                  "Pickled queryset instance's Django version is not specified.",
                  RuntimeWarning,
                  stacklevel=2,
              )
          self.__dict__.update(state)
  
      def __repr__(self):
          data = list(self[: REPR_OUTPUT_SIZE + 1])
          if len(data) > REPR_OUTPUT_SIZE:
              data[-1] = "...(remaining elements truncated)..."
          return "<%s %r>" % (self.__class__.__name__, data)
  
      def __len__(self):
          self._fetch_all()
          return len(self._result_cache)
  
      def __iter__(self):
          """
          The queryset iterator protocol uses three nested iterators in the
          default case:
              1. sql.compiler.execute_sql()
                 - Returns 100 rows at time (constants.GET_ITERATOR_CHUNK_SIZE)
                   using cursor.fetchmany(). This part is responsible for
                   doing some column masking, and returning the rows in chunks.
              2. sql.compiler.results_iter()
                 - Returns one row at time. At this point the rows are still just
                   tuples. In some cases the return values are converted to
                   Python values at this location.
              3. self.iterator()
                 - Responsible for turning the rows into model objects.
          """
          self._fetch_all()
          return iter(self._result_cache)
  
      def __bool__(self):
          self._fetch_all()
          return bool(self._result_cache)
  
      def __getitem__(self, k):
          """Retrieve an item or slice from the set of results."""
          if not isinstance(k, (int, slice)):
              raise TypeError(
                  "QuerySet indices must be integers or slices, not %s."
                  % type(k).__name__
              )
          if (isinstance(k, int) and k < 0) or (
              isinstance(k, slice)
              and (
                  (k.start is not None and k.start < 0)
                  or (k.stop is not None and k.stop < 0)
              )
          ):
              raise ValueError("Negative indexing is not supported.")
  
          if self._result_cache is not None:
              return self._result_cache[k]
  
          if isinstance(k, slice):
              qs = self._chain()
              if k.start is not None:
                  start = int(k.start)
              else:
                  start = None
              if k.stop is not None:
                  stop = int(k.stop)
              else:
                  stop = None
              qs.query.set_limits(start, stop)
              return list(qs)[:: k.step] if k.step else qs
  
          qs = self._chain()
          qs.query.set_limits(k, k + 1)
          qs._fetch_all()
          return qs._result_cache[0]
  
      def __class_getitem__(cls, *args, **kwargs):
          return cls
  
      def __and__(self, other):
          self._merge_sanity_check(other)
          if isinstance(other, EmptyQuerySet):
              return other
          if isinstance(self, EmptyQuerySet):
              return self
          combined = self._chain()
          combined._merge_known_related_objects(other)
          combined.query.combine(other.query, sql.AND)
          return combined
  
      def __or__(self, other):
          self._merge_sanity_check(other)
          if isinstance(self, EmptyQuerySet):
              return other
          if isinstance(other, EmptyQuerySet):
              return self
          query = (
              self
              if self.query.can_filter()
              else self.model._base_manager.filter(pk__in=self.values("pk"))
          )
          combined = query._chain()
          combined._merge_known_related_objects(other)
          if not other.query.can_filter():
              other = other.model._base_manager.filter(pk__in=other.values("pk"))
          combined.query.combine(other.query, sql.OR)
          return combined
  
      ####################################
      # METHODS THAT DO DATABASE QUERIES #
      ####################################
  
      def _iterator(self, use_chunked_fetch, chunk_size):
          yield from self._iterable_class(
              self, chunked_fetch=use_chunked_fetch, chunk_size=chunk_size
          )
  
      def iterator(self, chunk_size=2000):
          """
          An iterator over the results from applying this QuerySet to the
          database.
          """
          if chunk_size <= 0:
              raise ValueError("Chunk size must be strictly positive.")
          use_chunked_fetch = not connections[self.db].settings_dict.get(
              "DISABLE_SERVER_SIDE_CURSORS"
          )
          return self._iterator(use_chunked_fetch, chunk_size)
  
      def aggregate(self, *args, **kwargs):
          """
          Return a dictionary containing the calculations (aggregation)
          over the current queryset.
  
          If args is present the expression is passed as a kwarg using
          the Aggregate object's default alias.
          """
          if self.query.distinct_fields:
              raise NotImplementedError("aggregate() + distinct(fields) not implemented.")
          self._validate_values_are_expressions(
              (*args, *kwargs.values()), method_name="aggregate"
          )
          for arg in args:
              # The default_alias property raises TypeError if default_alias
              # can't be set automatically or AttributeError if it isn't an
              # attribute.
              try:
                  arg.default_alias
              except (AttributeError, TypeError):
                  raise TypeError("Complex aggregates require an alias")
              kwargs[arg.default_alias] = arg
  
          query = self.query.chain()
          for (alias, aggregate_expr) in kwargs.items():
              query.add_annotation(aggregate_expr, alias, is_summary=True)
              annotation = query.annotations[alias]
              if not annotation.contains_aggregate:
                  raise TypeError("%s is not an aggregate expression" % alias)
              for expr in annotation.get_source_expressions():
                  if (
                      expr.contains_aggregate
                      and isinstance(expr, Ref)
                      and expr.refs in kwargs
                  ):
                      name = expr.refs
                      raise exceptions.FieldError(
                          "Cannot compute %s('%s'): '%s' is an aggregate"
                          % (annotation.name, name, name)
                      )
          return query.get_aggregation(self.db, kwargs)
  
      def count(self):
          """
          Perform a SELECT COUNT() and return the number of records as an
          integer.
  
          If the QuerySet is already fully cached, return the length of the
          cached results set to avoid multiple SELECT COUNT(*) calls.
          """
          if self._result_cache is not None:
              return len(self._result_cache)
  
          return self.query.get_count(using=self.db)
  
      def get(self, *args, **kwargs):
          """
          Perform the query and return a single object matching the given
          keyword arguments.
          """
          if self.query.combinator and (args or kwargs):
              raise NotSupportedError(
                  "Calling QuerySet.get(...) with filters after %s() is not "
                  "supported." % self.query.combinator
              )
          clone = self._chain() if self.query.combinator else self.filter(*args, **kwargs)
          if self.query.can_filter() and not self.query.distinct_fields:
              clone = clone.order_by()
          limit = None
          if (
              not clone.query.select_for_update
              or connections[clone.db].features.supports_select_for_update_with_limit
          ):
              limit = MAX_GET_RESULTS
              clone.query.set_limits(high=limit)
          num = len(clone)
          if num == 1:
              return clone._result_cache[0]
          if not num:
              raise self.model.DoesNotExist(
                  "%s matching query does not exist." % self.model._meta.object_name
              )
          raise self.model.MultipleObjectsReturned(
              "get() returned more than one %s -- it returned %s!"
              % (
                  self.model._meta.object_name,
                  num if not limit or num < limit else "more than %s" % (limit - 1),
              )
          )
  
      def create(self, **kwargs):
          """
          Create a new object with the given kwargs, saving it to the database
          and returning the created object.
          """
          obj = self.model(**kwargs)
          self._for_write = True
          obj.save(force_insert=True, using=self.db)
          return obj
  
      def _prepare_for_bulk_create(self, objs):
          for obj in objs:
              if obj.pk is None:
                  # Populate new PK values.
                  obj.pk = obj._meta.pk.get_pk_value_on_save(obj)
              obj._prepare_related_fields_for_save(operation_name="bulk_create")
  
      def bulk_create(self, objs, batch_size=None, ignore_conflicts=False):
          """
          Insert each of the instances into the database. Do *not* call
          save() on each of the instances, do not send any pre/post_save
          signals, and do not set the primary key attribute if it is an
          autoincrement field (except if features.can_return_rows_from_bulk_insert=True).
          Multi-table models are not supported.
          """
          # When you bulk insert you don't get the primary keys back (if it's an
          # autoincrement, except if can_return_rows_from_bulk_insert=True), so
          # you can't insert into the child tables which references this. There
          # are two workarounds:
          # 1) This could be implemented if you didn't have an autoincrement pk
          # 2) You could do it by doing O(n) normal inserts into the parent
          #    tables to get the primary keys back and then doing a single bulk
          #    insert into the childmost table.
          # We currently set the primary keys on the objects when using
          # PostgreSQL via the RETURNING ID clause. It should be possible for
          # Oracle as well, but the semantics for extracting the primary keys is
          # trickier so it's not done yet.
          if batch_size is not None and batch_size <= 0:
              raise ValueError("Batch size must be a positive integer.")
          # Check that the parents share the same concrete model with the our
          # model to detect the inheritance pattern ConcreteGrandParent ->
          # MultiTableParent -> ProxyChild. Simply checking self.model._meta.proxy
          # would not identify that case as involving multiple tables.
          for parent in self.model._meta.get_parent_list():
              if parent._meta.concrete_model is not self.model._meta.concrete_model:
                  raise ValueError("Can't bulk create a multi-table inherited model")
          if not objs:
              return objs
          self._for_write = True
          connection = connections[self.db]
          opts = self.model._meta
          fields = opts.concrete_fields
          objs = list(objs)
          self._prepare_for_bulk_create(objs)
          with transaction.atomic(using=self.db, savepoint=False):
              objs_with_pk, objs_without_pk = partition(lambda o: o.pk is None, objs)
              if objs_with_pk:
                  returned_columns = self._batched_insert(
                      objs_with_pk,
                      fields,
                      batch_size,
                      ignore_conflicts=ignore_conflicts,
                  )
                  for obj_with_pk, results in zip(objs_with_pk, returned_columns):
                      for result, field in zip(results, opts.db_returning_fields):
                          if field != opts.pk:
                              setattr(obj_with_pk, field.attname, result)
                  for obj_with_pk in objs_with_pk:
                      obj_with_pk._state.adding = False
                      obj_with_pk._state.db = self.db
              if objs_without_pk:
                  fields = [f for f in fields if not isinstance(f, AutoField)]
                  returned_columns = self._batched_insert(
                      objs_without_pk,
                      fields,
                      batch_size,
                      ignore_conflicts=ignore_conflicts,
                  )
                  if (
                      connection.features.can_return_rows_from_bulk_insert
                      and not ignore_conflicts
                  ):
                      assert len(returned_columns) == len(objs_without_pk)
                  for obj_without_pk, results in zip(objs_without_pk, returned_columns):
                      for result, field in zip(results, opts.db_returning_fields):
                          setattr(obj_without_pk, field.attname, result)
                      obj_without_pk._state.adding = False
                      obj_without_pk._state.db = self.db
  
          return objs
  
      def bulk_update(self, objs, fields, batch_size=None):
          """
          Update the given fields in each of the given objects in the database.
          """
          if batch_size is not None and batch_size < 0:
              raise ValueError("Batch size must be a positive integer.")
          if not fields:
              raise ValueError("Field names must be given to bulk_update().")
          objs = tuple(objs)
          if any(obj.pk is None for obj in objs):
              raise ValueError("All bulk_update() objects must have a primary key set.")
          fields = [self.model._meta.get_field(name) for name in fields]
          if any(not f.concrete or f.many_to_many for f in fields):
              raise ValueError("bulk_update() can only be used with concrete fields.")
          if any(f.primary_key for f in fields):
              raise ValueError("bulk_update() cannot be used with primary key fields.")
          if not objs:
              return 0
          # PK is used twice in the resulting update query, once in the filter
          # and once in the WHEN. Each field will also have one CAST.
          max_batch_size = connections[self.db].ops.bulk_batch_size(
              ["pk", "pk"] + fields, objs
          )
          batch_size = min(batch_size, max_batch_size) if batch_size else max_batch_size
          requires_casting = connections[self.db].features.requires_casted_case_in_updates
          batches = (objs[i : i + batch_size] for i in range(0, len(objs), batch_size))
          updates = []
          for batch_objs in batches:
              update_kwargs = {}
              for field in fields:
                  when_statements = []
                  for obj in batch_objs:
                      attr = getattr(obj, field.attname)
                      if not isinstance(attr, Expression):
                          attr = Value(attr, output_field=field)
                      when_statements.append(When(pk=obj.pk, then=attr))
                  case_statement = Case(*when_statements, output_field=field)
                  if requires_casting:
                      case_statement = Cast(case_statement, output_field=field)
                  update_kwargs[field.attname] = case_statement
              updates.append(([obj.pk for obj in batch_objs], update_kwargs))
          rows_updated = 0
          with transaction.atomic(using=self.db, savepoint=False):
              for pks, update_kwargs in updates:
                  rows_updated += self.filter(pk__in=pks).update(**update_kwargs)
          return rows_updated
  
      bulk_update.alters_data = True
  
      def get_or_create(self, defaults=None, **kwargs):
          """
          Look up an object with the given kwargs, creating one if necessary.
          Return a tuple of (object, created), where created is a boolean
          specifying whether an object was created.
          """
          # The get() needs to be targeted at the write database in order
          # to avoid potential transaction consistency problems.
          self._for_write = True
          try:
              return self.get(**kwargs), False
          except self.model.DoesNotExist:
              params = self._extract_model_params(defaults, **kwargs)
              # Try to create an object using passed params.
              try:
                  with transaction.atomic(using=self.db):
                      params = dict(resolve_callables(params))
                      return self.create(**params), True
              except IntegrityError:
                  try:
                      return self.get(**kwargs), False
                  except self.model.DoesNotExist:
                      pass
                  raise
  
      def update_or_create(self, defaults=None, **kwargs):
          """
          Look up an object with the given kwargs, updating one with defaults
          if it exists, otherwise create a new one.
          Return a tuple (object, created), where created is a boolean
          specifying whether an object was created.
          """
          defaults = defaults or {}
          self._for_write = True
          with transaction.atomic(using=self.db):
              # Lock the row so that a concurrent update is blocked until
              # update_or_create() has performed its save.
              obj, created = self.select_for_update().get_or_create(defaults, **kwargs)
              if created:
                  return obj, created
              for k, v in resolve_callables(defaults):
                  setattr(obj, k, v)
              obj.save(using=self.db)
          return obj, False
  
      def _extract_model_params(self, defaults, **kwargs):
          """
          Prepare `params` for creating a model instance based on the given
          kwargs; for use by get_or_create().
          """
          defaults = defaults or {}
          params = {k: v for k, v in kwargs.items() if LOOKUP_SEP not in k}
          params.update(defaults)
          property_names = self.model._meta._property_names
          invalid_params = []
          for param in params:
              try:
                  self.model._meta.get_field(param)
              except exceptions.FieldDoesNotExist:
                  # It's okay to use a model's property if it has a setter.
                  if not (param in property_names and getattr(self.model, param).fset):
                      invalid_params.append(param)
          if invalid_params:
              raise exceptions.FieldError(
                  "Invalid field name(s) for model %s: '%s'."
                  % (
                      self.model._meta.object_name,
                      "', '".join(sorted(invalid_params)),
                  )
              )
          return params
  
      def _earliest(self, *fields):
          """
          Return the earliest object according to fields (if given) or by the
          model's Meta.get_latest_by.
          """
          if fields:
              order_by = fields
          else:
              order_by = getattr(self.model._meta, "get_latest_by")
              if order_by and not isinstance(order_by, (tuple, list)):
                  order_by = (order_by,)
          if order_by is None:
              raise ValueError(
                  "earliest() and latest() require either fields as positional "
                  "arguments or 'get_latest_by' in the model's Meta."
              )
          obj = self._chain()
          obj.query.set_limits(high=1)
          obj.query.clear_ordering(force=True)
          obj.query.add_ordering(*order_by)
          return obj.get()
  
      def earliest(self, *fields):
          if self.query.is_sliced:
              raise TypeError("Cannot change a query once a slice has been taken.")
          return self._earliest(*fields)
  
      def latest(self, *fields):
          if self.query.is_sliced:
              raise TypeError("Cannot change a query once a slice has been taken.")
          return self.reverse()._earliest(*fields)
  
      def first(self):
          """Return the first object of a query or None if no match is found."""
          for obj in (self if self.ordered else self.order_by("pk"))[:1]:
              return obj
  
      def last(self):
          """Return the last object of a query or None if no match is found."""
          for obj in (self.reverse() if self.ordered else self.order_by("-pk"))[:1]:
              return obj
  
      def in_bulk(self, id_list=None, *, field_name="pk"):
          """
          Return a dictionary mapping each of the given IDs to the object with
          that ID. If `id_list` isn't provided, evaluate the entire QuerySet.
          """
          if self.query.is_sliced:
              raise TypeError("Cannot use 'limit' or 'offset' with in_bulk().")
          opts = self.model._meta
          unique_fields = [
              constraint.fields[0]
              for constraint in opts.total_unique_constraints
              if len(constraint.fields) == 1
          ]
          if (
              field_name != "pk"
              and not opts.get_field(field_name).unique
              and field_name not in unique_fields
              and self.query.distinct_fields != (field_name,)
          ):
              raise ValueError(
                  "in_bulk()'s field_name must be a unique field but %r isn't."
                  % field_name
              )
          if id_list is not None:
              if not id_list:
                  return {}
              filter_key = "{}__in".format(field_name)
              batch_size = connections[self.db].features.max_query_params
              id_list = tuple(id_list)
              # If the database has a limit on the number of query parameters
              # (e.g. SQLite), retrieve objects in batches if necessary.
              if batch_size and batch_size < len(id_list):
                  qs = ()
                  for offset in range(0, len(id_list), batch_size):
                      batch = id_list[offset : offset + batch_size]
                      qs += tuple(self.filter(**{filter_key: batch}).order_by())
              else:
                  qs = self.filter(**{filter_key: id_list}).order_by()
          else:
              qs = self._chain()
          return {getattr(obj, field_name): obj for obj in qs}
  
      def delete(self):
          """Delete the records in the current QuerySet."""
          self._not_support_combined_queries("delete")
          if self.query.is_sliced:
              raise TypeError("Cannot use 'limit' or 'offset' with delete().")
          if self.query.distinct or self.query.distinct_fields:
              raise TypeError("Cannot call delete() after .distinct().")
          if self._fields is not None:
              raise TypeError("Cannot call delete() after .values() or .values_list()")
  
          del_query = self._chain()
  
          # The delete is actually 2 queries - one to find related objects,
          # and one to delete. Make sure that the discovery of related
          # objects is performed on the same database as the deletion.
          del_query._for_write = True
  
          # Disable non-supported fields.
          del_query.query.select_for_update = False
          del_query.query.select_related = False
          del_query.query.clear_ordering(force=True)
  
          collector = Collector(using=del_query.db)
          collector.collect(del_query)
          deleted, _rows_count = collector.delete()
  
          # Clear the result cache, in case this QuerySet gets reused.
          self._result_cache = None
          return deleted, _rows_count
  
      delete.alters_data = True
      delete.queryset_only = True
  
      def _raw_delete(self, using):
          """
          Delete objects found from the given queryset in single direct SQL
          query. No signals are sent and there is no protection for cascades.
          """
          query = self.query.clone()
          query.__class__ = sql.DeleteQuery
          cursor = query.get_compiler(using).execute_sql(CURSOR)
          if cursor:
              with cursor:
                  return cursor.rowcount
          return 0
  
      _raw_delete.alters_data = True
  
      def update(self, **kwargs):
          """
          Update all elements in the current QuerySet, setting all the given
          fields to the appropriate values.
          """
          self._not_support_combined_queries("update")
          if self.query.is_sliced:
              raise TypeError("Cannot update a query once a slice has been taken.")
          self._for_write = True
          query = self.query.chain(sql.UpdateQuery)
          query.add_update_values(kwargs)
          # Clear any annotations so that they won't be present in subqueries.
          query.annotations = {}
          with transaction.mark_for_rollback_on_error(using=self.db):
              rows = query.get_compiler(self.db).execute_sql(CURSOR)
          self._result_cache = None
          return rows
  
      update.alters_data = True
  
      def _update(self, values):
          """
          A version of update() that accepts field objects instead of field names.
          Used primarily for model saving and not intended for use by general
          code (it requires too much poking around at model internals to be
          useful at that level).
          """
          if self.query.is_sliced:
              raise TypeError("Cannot update a query once a slice has been taken.")
          query = self.query.chain(sql.UpdateQuery)
          query.add_update_fields(values)
          # Clear any annotations so that they won't be present in subqueries.
          query.annotations = {}
          self._result_cache = None
          return query.get_compiler(self.db).execute_sql(CURSOR)
  
      _update.alters_data = True
      _update.queryset_only = False
  
      def exists(self):
          if self._result_cache is None:
              return self.query.has_results(using=self.db)
          return bool(self._result_cache)
  
      def contains(self, obj):
          """Return True if the queryset contains an object."""
          self._not_support_combined_queries("contains")
          if self._fields is not None:
              raise TypeError(
                  "Cannot call QuerySet.contains() after .values() or .values_list()."
              )
          try:
              if obj._meta.concrete_model != self.model._meta.concrete_model:
                  return False
          except AttributeError:
              raise TypeError("'obj' must be a model instance.")
          if obj.pk is None:
              raise ValueError("QuerySet.contains() cannot be used on unsaved objects.")
          if self._result_cache is not None:
              return obj in self._result_cache
          return self.filter(pk=obj.pk).exists()
  
      def _prefetch_related_objects(self):
          # This method can only be called once the result cache has been filled.
          prefetch_related_objects(self._result_cache, *self._prefetch_related_lookups)
          self._prefetch_done = True
  
      def explain(self, *, format=None, **options):
          return self.query.explain(using=self.db, format=format, **options)
  
      ##################################################
      # PUBLIC METHODS THAT RETURN A QUERYSET SUBCLASS #
      ##################################################
  
      def raw(self, raw_query, params=(), translations=None, using=None):
          if using is None:
              using = self.db
          qs = RawQuerySet(
              raw_query,
              model=self.model,
              params=params,
              translations=translations,
              using=using,
          )
          qs._prefetch_related_lookups = self._prefetch_related_lookups[:]
          return qs
  
      def _values(self, *fields, **expressions):
          clone = self._chain()
          if expressions:
              clone = clone.annotate(**expressions)
          clone._fields = fields
          clone.query.set_values(fields)
          return clone
  
      def values(self, *fields, **expressions):
          fields += tuple(expressions)
          clone = self._values(*fields, **expressions)
          clone._iterable_class = ValuesIterable
          return clone
  
      def values_list(self, *fields, flat=False, named=False):
          if flat and named:
              raise TypeError("'flat' and 'named' can't be used together.")
          if flat and len(fields) > 1:
              raise TypeError(
                  "'flat' is not valid when values_list is called with more than one "
                  "field."
              )
  
          field_names = {f for f in fields if not hasattr(f, "resolve_expression")}
          _fields = []
          expressions = {}
          counter = 1
          for field in fields:
              if hasattr(field, "resolve_expression"):
                  field_id_prefix = getattr(
                      field, "default_alias", field.__class__.__name__.lower()
                  )
                  while True:
                      field_id = field_id_prefix + str(counter)
                      counter += 1
                      if field_id not in field_names:
                          break
                  expressions[field_id] = field
                  _fields.append(field_id)
              else:
                  _fields.append(field)
  
          clone = self._values(*_fields, **expressions)
          clone._iterable_class = (
              NamedValuesListIterable
              if named
              else FlatValuesListIterable
              if flat
              else ValuesListIterable
          )
          return clone
  
      def dates(self, field_name, kind, order="ASC"):
          """
          Return a list of date objects representing all available dates for
          the given field_name, scoped to 'kind'.
          """
          if kind not in ("year", "month", "week", "day"):
              raise ValueError("'kind' must be one of 'year', 'month', 'week', or 'day'.")
          if order not in ("ASC", "DESC"):
              raise ValueError("'order' must be either 'ASC' or 'DESC'.")
          return (
              self.annotate(
                  datefield=Trunc(field_name, kind, output_field=DateField()),
                  plain_field=F(field_name),
              )
              .values_list("datefield", flat=True)
              .distinct()
              .filter(plain_field__isnull=False)
              .order_by(("-" if order == "DESC" else "") + "datefield")
          )
  
      # RemovedInDjango50Warning: when the deprecation ends, remove is_dst
      # argument.
      def datetimes(
          self, field_name, kind, order="ASC", tzinfo=None, is_dst=timezone.NOT_PASSED
      ):
          """
          Return a list of datetime objects representing all available
          datetimes for the given field_name, scoped to 'kind'.
          """
          if kind not in ("year", "month", "week", "day", "hour", "minute", "second"):
              raise ValueError(
                  "'kind' must be one of 'year', 'month', 'week', 'day', "
                  "'hour', 'minute', or 'second'."
              )
          if order not in ("ASC", "DESC"):
              raise ValueError("'order' must be either 'ASC' or 'DESC'.")
          if settings.USE_TZ:
              if tzinfo is None:
                  tzinfo = timezone.get_current_timezone()
          else:
              tzinfo = None
          return (
              self.annotate(
                  datetimefield=Trunc(
                      field_name,
                      kind,
                      output_field=DateTimeField(),
                      tzinfo=tzinfo,
                      is_dst=is_dst,
                  ),
                  plain_field=F(field_name),
              )
              .values_list("datetimefield", flat=True)
              .distinct()
              .filter(plain_field__isnull=False)
              .order_by(("-" if order == "DESC" else "") + "datetimefield")
          )
  
      def none(self):
          """Return an empty QuerySet."""
          clone = self._chain()
          clone.query.set_empty()
          return clone
  
      ##################################################################
      # PUBLIC METHODS THAT ALTER ATTRIBUTES AND RETURN A NEW QUERYSET #
      ##################################################################
  
      def all(self):
          """
          Return a new QuerySet that is a copy of the current one. This allows a
          QuerySet to proxy for a model manager in some cases.
          """
          return self._chain()
  
      def filter(self, *args, **kwargs):
          """
          Return a new QuerySet instance with the args ANDed to the existing
          set.
          """
          self._not_support_combined_queries("filter")
          return self._filter_or_exclude(False, args, kwargs)
  
      def exclude(self, *args, **kwargs):
          """
          Return a new QuerySet instance with NOT (args) ANDed to the existing
          set.
          """
          self._not_support_combined_queries("exclude")
          return self._filter_or_exclude(True, args, kwargs)
  
      def _filter_or_exclude(self, negate, args, kwargs):
          if (args or kwargs) and self.query.is_sliced:
              raise TypeError("Cannot filter a query once a slice has been taken.")
          clone = self._chain()
          if self._defer_next_filter:
              self._defer_next_filter = False
              clone._deferred_filter = negate, args, kwargs
          else:
              clone._filter_or_exclude_inplace(negate, args, kwargs)
          return clone
  
      def _filter_or_exclude_inplace(self, negate, args, kwargs):
          if negate:
              self._query.add_q(~Q(*args, **kwargs))
          else:
              self._query.add_q(Q(*args, **kwargs))
  
      def complex_filter(self, filter_obj):
          """
          Return a new QuerySet instance with filter_obj added to the filters.
  
          filter_obj can be a Q object or a dictionary of keyword lookup
          arguments.
  
          This exists to support framework features such as 'limit_choices_to',
          and usually it will be more natural to use other methods.
          """
          if isinstance(filter_obj, Q):
              clone = self._chain()
              clone.query.add_q(filter_obj)
              return clone
          else:
              return self._filter_or_exclude(False, args=(), kwargs=filter_obj)
  
      def _combinator_query(self, combinator, *other_qs, all=False):
          # Clone the query to inherit the select list and everything
          clone = self._chain()
          # Clear limits and ordering so they can be reapplied
          clone.query.clear_ordering(force=True)
          clone.query.clear_limits()
          clone.query.combined_queries = (self.query,) + tuple(
              qs.query for qs in other_qs
          )
          clone.query.combinator = combinator
          clone.query.combinator_all = all
          return clone
  
      def union(self, *other_qs, all=False):
          # If the query is an EmptyQuerySet, combine all nonempty querysets.
          if isinstance(self, EmptyQuerySet):
              qs = [q for q in other_qs if not isinstance(q, EmptyQuerySet)]
              if not qs:
                  return self
              if len(qs) == 1:
                  return qs[0]
              return qs[0]._combinator_query("union", *qs[1:], all=all)
          return self._combinator_query("union", *other_qs, all=all)
  
      def intersection(self, *other_qs):
          # If any query is an EmptyQuerySet, return it.
          if isinstance(self, EmptyQuerySet):
              return self
          for other in other_qs:
              if isinstance(other, EmptyQuerySet):
                  return other
          return self._combinator_query("intersection", *other_qs)
  
      def difference(self, *other_qs):
          # If the query is an EmptyQuerySet, return it.
          if isinstance(self, EmptyQuerySet):
              return self
          return self._combinator_query("difference", *other_qs)
  
      def select_for_update(self, nowait=False, skip_locked=False, of=(), no_key=False):
          """
          Return a new QuerySet instance that will select objects with a
          FOR UPDATE lock.
          """
          if nowait and skip_locked:
              raise ValueError("The nowait option cannot be used with skip_locked.")
          obj = self._chain()
          obj._for_write = True
          obj.query.select_for_update = True
          obj.query.select_for_update_nowait = nowait
          obj.query.select_for_update_skip_locked = skip_locked
          obj.query.select_for_update_of = of
          obj.query.select_for_no_key_update = no_key
          return obj
  
      def select_related(self, *fields):
          """
          Return a new QuerySet instance that will select related objects.
  
          If fields are specified, they must be ForeignKey fields and only those
          related objects are included in the selection.
  
          If select_related(None) is called, clear the list.
          """
          self._not_support_combined_queries("select_related")
          if self._fields is not None:
              raise TypeError(
                  "Cannot call select_related() after .values() or .values_list()"
              )
  
          obj = self._chain()
          if fields == (None,):
              obj.query.select_related = False
          elif fields:
              obj.query.add_select_related(fields)
          else:
              obj.query.select_related = True
          return obj
  
      def prefetch_related(self, *lookups):
          """
          Return a new QuerySet instance that will prefetch the specified
          Many-To-One and Many-To-Many related objects when the QuerySet is
          evaluated.
  
          When prefetch_related() is called more than once, append to the list of
          prefetch lookups. If prefetch_related(None) is called, clear the list.
          """
          self._not_support_combined_queries("prefetch_related")
          clone = self._chain()
          if lookups == (None,):
              clone._prefetch_related_lookups = ()
          else:
              for lookup in lookups:
                  if isinstance(lookup, Prefetch):
                      lookup = lookup.prefetch_to
                  lookup = lookup.split(LOOKUP_SEP, 1)[0]
                  if lookup in self.query._filtered_relations:
                      raise ValueError(
                          "prefetch_related() is not supported with FilteredRelation."
                      )
              clone._prefetch_related_lookups = clone._prefetch_related_lookups + lookups
          return clone
  
      def annotate(self, *args, **kwargs):
          """
          Return a query set in which the returned objects have been annotated
          with extra data or aggregations.
          """
          self._not_support_combined_queries("annotate")
          return self._annotate(args, kwargs, select=True)
  
      def alias(self, *args, **kwargs):
          """
          Return a query set with added aliases for extra data or aggregations.
          """
          self._not_support_combined_queries("alias")
          return self._annotate(args, kwargs, select=False)
  
      def _annotate(self, args, kwargs, select=True):
          self._validate_values_are_expressions(
              args + tuple(kwargs.values()), method_name="annotate"
          )
          annotations = {}
          for arg in args:
              # The default_alias property may raise a TypeError.
              try:
                  if arg.default_alias in kwargs:
                      raise ValueError(
                          "The named annotation '%s' conflicts with the "
                          "default name for another annotation." % arg.default_alias
                      )
              except TypeError:
                  raise TypeError("Complex annotations require an alias")
              annotations[arg.default_alias] = arg
          annotations.update(kwargs)
  
          clone = self._chain()
          names = self._fields
          if names is None:
              names = set(
                  chain.from_iterable(
                      (field.name, field.attname)
                      if hasattr(field, "attname")
                      else (field.name,)
                      for field in self.model._meta.get_fields()
                  )
              )
  
          for alias, annotation in annotations.items():
              if alias in names:
                  raise ValueError(
                      "The annotation '%s' conflicts with a field on "
                      "the model." % alias
                  )
              if isinstance(annotation, FilteredRelation):
                  clone.query.add_filtered_relation(annotation, alias)
              else:
                  clone.query.add_annotation(
                      annotation,
                      alias,
                      is_summary=False,
                      select=select,
                  )
          for alias, annotation in clone.query.annotations.items():
              if alias in annotations and annotation.contains_aggregate:
                  if clone._fields is None:
                      clone.query.group_by = True
                  else:
                      clone.query.set_group_by()
                  break
  
          return clone
  
      def order_by(self, *field_names):
          """Return a new QuerySet instance with the ordering changed."""
          if self.query.is_sliced:
              raise TypeError("Cannot reorder a query once a slice has been taken.")
          obj = self._chain()
          obj.query.clear_ordering(force=True, clear_default=False)
          obj.query.add_ordering(*field_names)
          return obj
  
      def distinct(self, *field_names):
          """
          Return a new QuerySet instance that will select only distinct results.
          """
          self._not_support_combined_queries("distinct")
          if self.query.is_sliced:
              raise TypeError(
                  "Cannot create distinct fields once a slice has been taken."
              )
          obj = self._chain()
          obj.query.add_distinct_fields(*field_names)
          return obj
  
      def extra(
          self,
          select=None,
          where=None,
          params=None,
          tables=None,
          order_by=None,
          select_params=None,
      ):
          """Add extra SQL fragments to the query."""
          self._not_support_combined_queries("extra")
          if self.query.is_sliced:
              raise TypeError("Cannot change a query once a slice has been taken.")
          clone = self._chain()
          clone.query.add_extra(select, select_params, where, params, tables, order_by)
          return clone
  
      def reverse(self):
          """Reverse the ordering of the QuerySet."""
          if self.query.is_sliced:
              raise TypeError("Cannot reverse a query once a slice has been taken.")
          clone = self._chain()
          clone.query.standard_ordering = not clone.query.standard_ordering
          return clone
  
      def defer(self, *fields):
          """
          Defer the loading of data for certain fields until they are accessed.
          Add the set of deferred fields to any existing set of deferred fields.
          The only exception to this is if None is passed in as the only
          parameter, in which case removal all deferrals.
          """
          self._not_support_combined_queries("defer")
          if self._fields is not None:
              raise TypeError("Cannot call defer() after .values() or .values_list()")
          clone = self._chain()
          if fields == (None,):
              clone.query.clear_deferred_loading()
          else:
              clone.query.add_deferred_loading(fields)
          return clone
  
      def only(self, *fields):
          """
          Essentially, the opposite of defer(). Only the fields passed into this
          method and that are not already specified as deferred are loaded
          immediately when the queryset is evaluated.
          """
          self._not_support_combined_queries("only")
          if self._fields is not None:
              raise TypeError("Cannot call only() after .values() or .values_list()")
          if fields == (None,):
              # Can only pass None to defer(), not only(), as the rest option.
              # That won't stop people trying to do this, so let's be explicit.
              raise TypeError("Cannot pass None as an argument to only().")
          for field in fields:
              field = field.split(LOOKUP_SEP, 1)[0]
              if field in self.query._filtered_relations:
                  raise ValueError("only() is not supported with FilteredRelation.")
          clone = self._chain()
          clone.query.add_immediate_loading(fields)
          return clone
  
      def using(self, alias):
          """Select which database this QuerySet should execute against."""
          clone = self._chain()
          clone._db = alias
          return clone
  
      ###################################
      # PUBLIC INTROSPECTION ATTRIBUTES #
      ###################################
  
      @property
      def ordered(self):
          """
          Return True if the QuerySet is ordered -- i.e. has an order_by()
          clause or a default ordering on the model (or is empty).
          """
          if isinstance(self, EmptyQuerySet):
              return True
          if self.query.extra_order_by or self.query.order_by:
              return True
          elif (
              self.query.default_ordering
              and self.query.get_meta().ordering
              and
              # A default ordering doesn't affect GROUP BY queries.
              not self.query.group_by
          ):
              return True
          else:
              return False
  
      @property
      def db(self):
          """Return the database used if this query is executed now."""
          if self._for_write:
              return self._db or router.db_for_write(self.model, **self._hints)
          return self._db or router.db_for_read(self.model, **self._hints)
  
      ###################
      # PRIVATE METHODS #
      ###################
  
      def _insert(
          self,
          objs,
          fields,
          returning_fields=None,
          raw=False,
          using=None,
          ignore_conflicts=False,
      ):
          """
          Insert a new record for the given model. This provides an interface to
          the InsertQuery class and is how Model.save() is implemented.
          """
          self._for_write = True
          if using is None:
              using = self.db
          query = sql.InsertQuery(self.model, ignore_conflicts=ignore_conflicts)
          query.insert_values(fields, objs, raw=raw)
          return query.get_compiler(using=using).execute_sql(returning_fields)
  
      _insert.alters_data = True
      _insert.queryset_only = False
  
      def _batched_insert(self, objs, fields, batch_size, ignore_conflicts=False):
          """
          Helper method for bulk_create() to insert objs one batch at a time.
          """
          if (
              ignore_conflicts
              and not connections[self.db].features.supports_ignore_conflicts
          ):
              raise NotSupportedError(
                  "This database backend does not support ignoring conflicts."
              )
          ops = connections[self.db].ops
          max_batch_size = max(ops.bulk_batch_size(fields, objs), 1)
          batch_size = min(batch_size, max_batch_size) if batch_size else max_batch_size
          inserted_rows = []
          bulk_return = connections[self.db].features.can_return_rows_from_bulk_insert
          for item in [objs[i : i + batch_size] for i in range(0, len(objs), batch_size)]:
              if bulk_return and not ignore_conflicts:
                  inserted_rows.extend(
                      self._insert(
                          item,
                          fields=fields,
                          using=self.db,
                          returning_fields=self.model._meta.db_returning_fields,
                          ignore_conflicts=ignore_conflicts,
                      )
                  )
              else:
                  self._insert(
                      item,
                      fields=fields,
                      using=self.db,
                      ignore_conflicts=ignore_conflicts,
                  )
          return inserted_rows
  
      def _chain(self):
          """
          Return a copy of the current QuerySet that's ready for another
          operation.
          """
          obj = self._clone()
          if obj._sticky_filter:
              obj.query.filter_is_sticky = True
              obj._sticky_filter = False
          return obj
  
      def _clone(self):
          """
          Return a copy of the current QuerySet. A lightweight alternative
          to deepcopy().
          """
          c = self.__class__(
              model=self.model,
              query=self.query.chain(),
              using=self._db,
              hints=self._hints,
          )
          c._sticky_filter = self._sticky_filter
          c._for_write = self._for_write
          c._prefetch_related_lookups = self._prefetch_related_lookups[:]
          c._known_related_objects = self._known_related_objects
          c._iterable_class = self._iterable_class
          c._fields = self._fields
          return c
  
      def _fetch_all(self):
          if self._result_cache is None:
              self._result_cache = list(self._iterable_class(self))
          if self._prefetch_related_lookups and not self._prefetch_done:
              self._prefetch_related_objects()
  
      def _next_is_sticky(self):
          """
          Indicate that the next filter call and the one following that should
          be treated as a single filter. This is only important when it comes to
          determining when to reuse tables for many-to-many filters. Required so
          that we can filter naturally on the results of related managers.
  
          This doesn't return a clone of the current QuerySet (it returns
          "self"). The method is only used internally and should be immediately
          followed by a filter() that does create a clone.
          """
          self._sticky_filter = True
          return self
  
      def _merge_sanity_check(self, other):
          """Check that two QuerySet classes may be merged."""
          if self._fields is not None and (
              set(self.query.values_select) != set(other.query.values_select)
              or set(self.query.extra_select) != set(other.query.extra_select)
              or set(self.query.annotation_select) != set(other.query.annotation_select)
          ):
              raise TypeError(
                  "Merging '%s' classes must involve the same values in each case."
                  % self.__class__.__name__
              )
  
      def _merge_known_related_objects(self, other):
          """
          Keep track of all known related objects from either QuerySet instance.
          """
          for field, objects in other._known_related_objects.items():
              self._known_related_objects.setdefault(field, {}).update(objects)
  
      def resolve_expression(self, *args, **kwargs):
          if self._fields and len(self._fields) > 1:
              # values() queryset can only be used as nested queries
              # if they are set up to select only a single field.
              raise TypeError("Cannot use multi-field values as a filter value.")
          query = self.query.resolve_expression(*args, **kwargs)
          query._db = self._db
          return query
  
      resolve_expression.queryset_only = True
  
      def _add_hints(self, **hints):
          """
          Update hinting information for use by routers. Add new key/values or
          overwrite existing key/values.
          """
          self._hints.update(hints)
  
      def _has_filters(self):
          """
          Check if this QuerySet has any filtering going on. This isn't
          equivalent with checking if all objects are present in results, for
          example, qs[1:]._has_filters() -> False.
          """
          return self.query.has_filters()
  
      @staticmethod
      def _validate_values_are_expressions(values, method_name):
          invalid_args = sorted(
              str(arg) for arg in values if not hasattr(arg, "resolve_expression")
          )
          if invalid_args:
              raise TypeError(
                  "QuerySet.%s() received non-expression(s): %s."
                  % (
                      method_name,
                      ", ".join(invalid_args),
                  )
              )
  
      def _not_support_combined_queries(self, operation_name):
          if self.query.combinator:
              raise NotSupportedError(
                  "Calling QuerySet.%s() after %s() is not supported."
                  % (operation_name, self.query.combinator)
              )
  
  
  class InstanceCheckMeta(type):
      def __instancecheck__(self, instance):
          return isinstance(instance, QuerySet) and instance.query.is_empty()
  
  
  class EmptyQuerySet(metaclass=InstanceCheckMeta):
      """
      Marker class to checking if a queryset is empty by .none():
          isinstance(qs.none(), EmptyQuerySet) -> True
      """
  
      def __init__(self, *args, **kwargs):
          raise TypeError("EmptyQuerySet can't be instantiated")
  
  
  class RawQuerySet:
      """
      Provide an iterator which converts the results of raw SQL queries into
      annotated model instances.
      """
  
      def __init__(
          self,
          raw_query,
          model=None,
          query=None,
          params=(),
          translations=None,
          using=None,
          hints=None,
      ):
          self.raw_query = raw_query
          self.model = model
          self._db = using
          self._hints = hints or {}
          self.query = query or sql.RawQuery(sql=raw_query, using=self.db, params=params)
          self.params = params
          self.translations = translations or {}
          self._result_cache = None
          self._prefetch_related_lookups = ()
          self._prefetch_done = False
  
      def resolve_model_init_order(self):
          """Resolve the init field names and value positions."""
          converter = connections[self.db].introspection.identifier_converter
          model_init_fields = [
              f for f in self.model._meta.fields if converter(f.column) in self.columns
          ]
          annotation_fields = [
              (column, pos)
              for pos, column in enumerate(self.columns)
              if column not in self.model_fields
          ]
          model_init_order = [
              self.columns.index(converter(f.column)) for f in model_init_fields
          ]
          model_init_names = [f.attname for f in model_init_fields]
          return model_init_names, model_init_order, annotation_fields
  
      def prefetch_related(self, *lookups):
          """Same as QuerySet.prefetch_related()"""
          clone = self._clone()
          if lookups == (None,):
              clone._prefetch_related_lookups = ()
          else:
              clone._prefetch_related_lookups = clone._prefetch_related_lookups + lookups
          return clone
  
      def _prefetch_related_objects(self):
          prefetch_related_objects(self._result_cache, *self._prefetch_related_lookups)
          self._prefetch_done = True
  
      def _clone(self):
          """Same as QuerySet._clone()"""
          c = self.__class__(
              self.raw_query,
              model=self.model,
              query=self.query,
              params=self.params,
              translations=self.translations,
              using=self._db,
              hints=self._hints,
          )
          c._prefetch_related_lookups = self._prefetch_related_lookups[:]
          return c
  
      def _fetch_all(self):
          if self._result_cache is None:
              self._result_cache = list(self.iterator())
          if self._prefetch_related_lookups and not self._prefetch_done:
              self._prefetch_related_objects()
  
      def __len__(self):
          self._fetch_all()
          return len(self._result_cache)
  
      def __bool__(self):
          self._fetch_all()
          return bool(self._result_cache)
  
      def __iter__(self):
          self._fetch_all()
          return iter(self._result_cache)
  
      def iterator(self):
          # Cache some things for performance reasons outside the loop.
          db = self.db
          compiler = connections[db].ops.compiler("SQLCompiler")(
              self.query, connections[db], db
          )
  
          query = iter(self.query)
  
          try:
              (
                  model_init_names,
                  model_init_pos,
                  annotation_fields,
              ) = self.resolve_model_init_order()
              if self.model._meta.pk.attname not in model_init_names:
                  raise exceptions.FieldDoesNotExist(
                      "Raw query must include the primary key"
                  )
              model_cls = self.model
              fields = [self.model_fields.get(c) for c in self.columns]
              converters = compiler.get_converters(
                  [f.get_col(f.model._meta.db_table) if f else None for f in fields]
              )
              if converters:
                  query = compiler.apply_converters(query, converters)
              for values in query:
                  # Associate fields to values
                  model_init_values = [values[pos] for pos in model_init_pos]
                  instance = model_cls.from_db(db, model_init_names, model_init_values)
                  if annotation_fields:
                      for column, pos in annotation_fields:
                          setattr(instance, column, values[pos])
                  yield instance
          finally:
              # Done iterating the Query. If it has its own cursor, close it.
              if hasattr(self.query, "cursor") and self.query.cursor:
                  self.query.cursor.close()
  
      def __repr__(self):
          return "<%s: %s>" % (self.__class__.__name__, self.query)
  
      def __getitem__(self, k):
          return list(self)[k]
  
      @property
      def db(self):
          """Return the database used if this query is executed now."""
          return self._db or router.db_for_read(self.model, **self._hints)
  
      def using(self, alias):
          """Select the database this RawQuerySet should execute against."""
          return RawQuerySet(
              self.raw_query,
              model=self.model,
              query=self.query.chain(using=alias),
              params=self.params,
              translations=self.translations,
              using=alias,
          )
  
      @cached_property
      def columns(self):
          """
          A list of model field names in the order they'll appear in the
          query results.
          """
          columns = self.query.get_columns()
          # Adjust any column names which don't match field names
          for (query_name, model_name) in self.translations.items():
              # Ignore translations for nonexistent column names
              try:
                  index = columns.index(query_name)
              except ValueError:
                  pass
              else:
                  columns[index] = model_name
          return columns
  
      @cached_property
      def model_fields(self):
          """A dict mapping column names to model field names."""
          converter = connections[self.db].introspection.identifier_converter
          model_fields = {}
          for field in self.model._meta.fields:
              name, column = field.get_attname_column()
              model_fields[converter(column)] = field
          return model_fields
  
  
  class Prefetch:
      def __init__(self, lookup, queryset=None, to_attr=None):
          # `prefetch_through` is the path we traverse to perform the prefetch.
          self.prefetch_through = lookup
          # `prefetch_to` is the path to the attribute that stores the result.
          self.prefetch_to = lookup
          if queryset is not None and (
              isinstance(queryset, RawQuerySet)
              or (
                  hasattr(queryset, "_iterable_class")
                  and not issubclass(queryset._iterable_class, ModelIterable)
              )
          ):
              raise ValueError(
                  "Prefetch querysets cannot use raw(), values(), and values_list()."
              )
          if to_attr:
              self.prefetch_to = LOOKUP_SEP.join(
                  lookup.split(LOOKUP_SEP)[:-1] + [to_attr]
              )
  
          self.queryset = queryset
          self.to_attr = to_attr
  
      def __getstate__(self):
          obj_dict = self.__dict__.copy()
          if self.queryset is not None:
              queryset = self.queryset._chain()
              # Prevent the QuerySet from being evaluated
              queryset._result_cache = []
              queryset._prefetch_done = True
              obj_dict["queryset"] = queryset
          return obj_dict
  
      def add_prefix(self, prefix):
          self.prefetch_through = prefix + LOOKUP_SEP + self.prefetch_through
          self.prefetch_to = prefix + LOOKUP_SEP + self.prefetch_to
  
      def get_current_prefetch_to(self, level):
          return LOOKUP_SEP.join(self.prefetch_to.split(LOOKUP_SEP)[: level + 1])
  
      def get_current_to_attr(self, level):
          parts = self.prefetch_to.split(LOOKUP_SEP)
          to_attr = parts[level]
          as_attr = self.to_attr and level == len(parts) - 1
          return to_attr, as_attr
  
      def get_current_queryset(self, level):
          if self.get_current_prefetch_to(level) == self.prefetch_to:
              return self.queryset
          return None
  
      def __eq__(self, other):
          if not isinstance(other, Prefetch):
              return NotImplemented
          return self.prefetch_to == other.prefetch_to
  
      def __hash__(self):
          return hash((self.__class__, self.prefetch_to))
  
  
  def normalize_prefetch_lookups(lookups, prefix=None):
      """Normalize lookups into Prefetch objects."""
      ret = []
      for lookup in lookups:
          if not isinstance(lookup, Prefetch):
              lookup = Prefetch(lookup)
          if prefix:
              lookup.add_prefix(prefix)
          ret.append(lookup)
      return ret
  
  
  def prefetch_related_objects(model_instances, *related_lookups):
      """
      Populate prefetched object caches for a list of model instances based on
      the lookups/Prefetch instances given.
      """
      if not model_instances:
          return  # nothing to do
  
      # We need to be able to dynamically add to the list of prefetch_related
      # lookups that we look up (see below).  So we need some book keeping to
      # ensure we don't do duplicate work.
      done_queries = {}  # dictionary of things like 'foo__bar': [results]
  
      auto_lookups = set()  # we add to this as we go through.
      followed_descriptors = set()  # recursion protection
  
      all_lookups = normalize_prefetch_lookups(reversed(related_lookups))
      while all_lookups:
          lookup = all_lookups.pop()
          if lookup.prefetch_to in done_queries:
              if lookup.queryset is not None:
                  raise ValueError(
                      "'%s' lookup was already seen with a different queryset. "
                      "You may need to adjust the ordering of your lookups."
                      % lookup.prefetch_to
                  )
  
              continue
  
          # Top level, the list of objects to decorate is the result cache
          # from the primary QuerySet. It won't be for deeper levels.
          obj_list = model_instances
  
          through_attrs = lookup.prefetch_through.split(LOOKUP_SEP)
          for level, through_attr in enumerate(through_attrs):
              # Prepare main instances
              if not obj_list:
                  break
  
              prefetch_to = lookup.get_current_prefetch_to(level)
              if prefetch_to in done_queries:
                  # Skip any prefetching, and any object preparation
                  obj_list = done_queries[prefetch_to]
                  continue
  
              # Prepare objects:
              good_objects = True
              for obj in obj_list:
                  # Since prefetching can re-use instances, it is possible to have
                  # the same instance multiple times in obj_list, so obj might
                  # already be prepared.
                  if not hasattr(obj, "_prefetched_objects_cache"):
                      try:
                          obj._prefetched_objects_cache = {}
                      except (AttributeError, TypeError):
                          # Must be an immutable object from
                          # values_list(flat=True), for example (TypeError) or
                          # a QuerySet subclass that isn't returning Model
                          # instances (AttributeError), either in Django or a 3rd
                          # party. prefetch_related() doesn't make sense, so quit.
                          good_objects = False
                          break
              if not good_objects:
                  break
  
              # Descend down tree
  
              # We assume that objects retrieved are homogeneous (which is the premise
              # of prefetch_related), so what applies to first object applies to all.
              first_obj = obj_list[0]
              to_attr = lookup.get_current_to_attr(level)[0]
              prefetcher, descriptor, attr_found, is_fetched = get_prefetcher(
                  first_obj, through_attr, to_attr
              )
  
              if not attr_found:
                  raise AttributeError(
                      "Cannot find '%s' on %s object, '%s' is an invalid "
                      "parameter to prefetch_related()"
                      % (
                          through_attr,
                          first_obj.__class__.__name__,
                          lookup.prefetch_through,
                      )
                  )
  
              if level == len(through_attrs) - 1 and prefetcher is None:
                  # Last one, this *must* resolve to something that supports
                  # prefetching, otherwise there is no point adding it and the
                  # developer asking for it has made a mistake.
                  raise ValueError(
                      "'%s' does not resolve to an item that supports "
                      "prefetching - this is an invalid parameter to "
                      "prefetch_related()." % lookup.prefetch_through
                  )
  
              obj_to_fetch = None
              if prefetcher is not None:
                  obj_to_fetch = [obj for obj in obj_list if not is_fetched(obj)]
  
              if obj_to_fetch:
                  obj_list, additional_lookups = prefetch_one_level(
                      obj_to_fetch,
                      prefetcher,
                      lookup,
                      level,
                  )
                  # We need to ensure we don't keep adding lookups from the
                  # same relationships to stop infinite recursion. So, if we
                  # are already on an automatically added lookup, don't add
                  # the new lookups from relationships we've seen already.
                  if not (
                      prefetch_to in done_queries
                      and lookup in auto_lookups
                      and descriptor in followed_descriptors
                  ):
                      done_queries[prefetch_to] = obj_list
                      new_lookups = normalize_prefetch_lookups(
                          reversed(additional_lookups), prefetch_to
                      )
                      auto_lookups.update(new_lookups)
                      all_lookups.extend(new_lookups)
                  followed_descriptors.add(descriptor)
              else:
                  # Either a singly related object that has already been fetched
                  # (e.g. via select_related), or hopefully some other property
                  # that doesn't support prefetching but needs to be traversed.
  
                  # We replace the current list of parent objects with the list
                  # of related objects, filtering out empty or missing values so
                  # that we can continue with nullable or reverse relations.
                  new_obj_list = []
                  for obj in obj_list:
                      if through_attr in getattr(obj, "_prefetched_objects_cache", ()):
                          # If related objects have been prefetched, use the
                          # cache rather than the object's through_attr.
                          new_obj = list(obj._prefetched_objects_cache.get(through_attr))
                      else:
                          try:
                              new_obj = getattr(obj, through_attr)
                          except exceptions.ObjectDoesNotExist:
                              continue
                      if new_obj is None:
                          continue
                      # We special-case `list` rather than something more generic
                      # like `Iterable` because we don't want to accidentally match
                      # user models that define __iter__.
                      if isinstance(new_obj, list):
                          new_obj_list.extend(new_obj)
                      else:
                          new_obj_list.append(new_obj)
                  obj_list = new_obj_list
  
  
  def get_prefetcher(instance, through_attr, to_attr):
      """
      For the attribute 'through_attr' on the given instance, find
      an object that has a get_prefetch_queryset().
      Return a 4 tuple containing:
      (the object with get_prefetch_queryset (or None),
       the descriptor object representing this relationship (or None),
       a boolean that is False if the attribute was not found at all,
       a function that takes an instance and returns a boolean that is True if
       the attribute has already been fetched for that instance)
      """
  
      def has_to_attr_attribute(instance):
          return hasattr(instance, to_attr)
  
      prefetcher = None
      is_fetched = has_to_attr_attribute
  
      # For singly related objects, we have to avoid getting the attribute
      # from the object, as this will trigger the query. So we first try
      # on the class, in order to get the descriptor object.
      rel_obj_descriptor = getattr(instance.__class__, through_attr, None)
      if rel_obj_descriptor is None:
          attr_found = hasattr(instance, through_attr)
      else:
          attr_found = True
          if rel_obj_descriptor:
              # singly related object, descriptor object has the
              # get_prefetch_queryset() method.
              if hasattr(rel_obj_descriptor, "get_prefetch_queryset"):
                  prefetcher = rel_obj_descriptor
                  is_fetched = rel_obj_descriptor.is_cached
              else:
                  # descriptor doesn't support prefetching, so we go ahead and get
                  # the attribute on the instance rather than the class to
                  # support many related managers
                  rel_obj = getattr(instance, through_attr)
                  if hasattr(rel_obj, "get_prefetch_queryset"):
                      prefetcher = rel_obj
                  if through_attr != to_attr:
                      # Special case cached_property instances because hasattr
                      # triggers attribute computation and assignment.
                      if isinstance(
                          getattr(instance.__class__, to_attr, None), cached_property
                      ):
  
                          def has_cached_property(instance):
                              return to_attr in instance.__dict__
  
                          is_fetched = has_cached_property
                  else:
  
                      def in_prefetched_cache(instance):
                          return through_attr in instance._prefetched_objects_cache
  
                      is_fetched = in_prefetched_cache
      return prefetcher, rel_obj_descriptor, attr_found, is_fetched
  
  
  def prefetch_one_level(instances, prefetcher, lookup, level):
      """
      Helper function for prefetch_related_objects().
  
      Run prefetches on all instances using the prefetcher object,
      assigning results to relevant caches in instance.
  
      Return the prefetched objects along with any additional prefetches that
      must be done due to prefetch_related lookups found from default managers.
      """
      # prefetcher must have a method get_prefetch_queryset() which takes a list
      # of instances, and returns a tuple:
  
      # (queryset of instances of self.model that are related to passed in instances,
      #  callable that gets value to be matched for returned instances,
      #  callable that gets value to be matched for passed in instances,
      #  boolean that is True for singly related objects,
      #  cache or field name to assign to,
      #  boolean that is True when the previous argument is a cache name vs a field name).
  
      # The 'values to be matched' must be hashable as they will be used
      # in a dictionary.
  
      (
          rel_qs,
          rel_obj_attr,
          instance_attr,
          single,
          cache_name,
          is_descriptor,
      ) = prefetcher.get_prefetch_queryset(instances, lookup.get_current_queryset(level))
      # We have to handle the possibility that the QuerySet we just got back
      # contains some prefetch_related lookups. We don't want to trigger the
      # prefetch_related functionality by evaluating the query. Rather, we need
      # to merge in the prefetch_related lookups.
      # Copy the lookups in case it is a Prefetch object which could be reused
      # later (happens in nested prefetch_related).
      additional_lookups = [
          copy.copy(additional_lookup)
          for additional_lookup in getattr(rel_qs, "_prefetch_related_lookups", ())
      ]
      if additional_lookups:
          # Don't need to clone because the manager should have given us a fresh
          # instance, so we access an internal instead of using public interface
          # for performance reasons.
          rel_qs._prefetch_related_lookups = ()
  
      all_related_objects = list(rel_qs)
  
      rel_obj_cache = {}
      for rel_obj in all_related_objects:
          rel_attr_val = rel_obj_attr(rel_obj)
          rel_obj_cache.setdefault(rel_attr_val, []).append(rel_obj)
  
      to_attr, as_attr = lookup.get_current_to_attr(level)
      # Make sure `to_attr` does not conflict with a field.
      if as_attr and instances:
          # We assume that objects retrieved are homogeneous (which is the premise
          # of prefetch_related), so what applies to first object applies to all.
          model = instances[0].__class__
          try:
              model._meta.get_field(to_attr)
          except exceptions.FieldDoesNotExist:
              pass
          else:
              msg = "to_attr={} conflicts with a field on the {} model."
              raise ValueError(msg.format(to_attr, model.__name__))
  
      # Whether or not we're prefetching the last part of the lookup.
      leaf = len(lookup.prefetch_through.split(LOOKUP_SEP)) - 1 == level
  
      for obj in instances:
          instance_attr_val = instance_attr(obj)
          vals = rel_obj_cache.get(instance_attr_val, [])
  
          if single:
              val = vals[0] if vals else None
              if as_attr:
                  # A to_attr has been given for the prefetch.
                  setattr(obj, to_attr, val)
              elif is_descriptor:
                  # cache_name points to a field name in obj.
                  # This field is a descriptor for a related object.
                  setattr(obj, cache_name, val)
              else:
                  # No to_attr has been given for this prefetch operation and the
                  # cache_name does not point to a descriptor. Store the value of
                  # the field in the object's field cache.
                  obj._state.fields_cache[cache_name] = val
          else:
              if as_attr:
                  setattr(obj, to_attr, vals)
              else:
                  manager = getattr(obj, to_attr)
                  if leaf and lookup.queryset is not None:
                      qs = manager._apply_rel_filters(lookup.queryset)
                  else:
                      qs = manager.get_queryset()
                  qs._result_cache = vals
                  # We don't want the individual qs doing prefetch_related now,
                  # since we have merged this into the current work.
                  qs._prefetch_done = True
                  obj._prefetched_objects_cache[cache_name] = qs
      return all_related_objects, additional_lookups
  
  
  class RelatedPopulator:
      """
      RelatedPopulator is used for select_related() object instantiation.
  
      The idea is that each select_related() model will be populated by a
      different RelatedPopulator instance. The RelatedPopulator instances get
      klass_info and select (computed in SQLCompiler) plus the used db as
      input for initialization. That data is used to compute which columns
      to use, how to instantiate the model, and how to populate the links
      between the objects.
  
      The actual creation of the objects is done in populate() method. This
      method gets row and from_obj as input and populates the select_related()
      model instance.
      """
  
      def __init__(self, klass_info, select, db):
          self.db = db
          # Pre-compute needed attributes. The attributes are:
          #  - model_cls: the possibly deferred model class to instantiate
          #  - either:
          #    - cols_start, cols_end: usually the columns in the row are
          #      in the same order model_cls.__init__ expects them, so we
          #      can instantiate by model_cls(*row[cols_start:cols_end])
          #    - reorder_for_init: When select_related descends to a child
          #      class, then we want to reuse the already selected parent
          #      data. However, in this case the parent data isn't necessarily
          #      in the same order that Model.__init__ expects it to be, so
          #      we have to reorder the parent data. The reorder_for_init
          #      attribute contains a function used to reorder the field data
          #      in the order __init__ expects it.
          #  - pk_idx: the index of the primary key field in the reordered
          #    model data. Used to check if a related object exists at all.
          #  - init_list: the field attnames fetched from the database. For
          #    deferred models this isn't the same as all attnames of the
          #    model's fields.
          #  - related_populators: a list of RelatedPopulator instances if
          #    select_related() descends to related models from this model.
          #  - local_setter, remote_setter: Methods to set cached values on
          #    the object being populated and on the remote object. Usually
          #    these are Field.set_cached_value() methods.
          select_fields = klass_info["select_fields"]
          from_parent = klass_info["from_parent"]
          if not from_parent:
              self.cols_start = select_fields[0]
              self.cols_end = select_fields[-1] + 1
              self.init_list = [
                  f[0].target.attname for f in select[self.cols_start : self.cols_end]
              ]
              self.reorder_for_init = None
          else:
              attname_indexes = {
                  select[idx][0].target.attname: idx for idx in select_fields
              }
              model_init_attnames = (
                  f.attname for f in klass_info["model"]._meta.concrete_fields
              )
              self.init_list = [
                  attname for attname in model_init_attnames if attname in attname_indexes
              ]
              self.reorder_for_init = operator.itemgetter(
                  *[attname_indexes[attname] for attname in self.init_list]
              )
  
          self.model_cls = klass_info["model"]
          self.pk_idx = self.init_list.index(self.model_cls._meta.pk.attname)
          self.related_populators = get_related_populators(klass_info, select, self.db)
          self.local_setter = klass_info["local_setter"]
          self.remote_setter = klass_info["remote_setter"]
  
      def populate(self, row, from_obj):
          if self.reorder_for_init:
              obj_data = self.reorder_for_init(row)
          else:
              obj_data = row[self.cols_start : self.cols_end]
          if obj_data[self.pk_idx] is None:
              obj = None
          else:
              obj = self.model_cls.from_db(self.db, self.init_list, obj_data)
              for rel_iter in self.related_populators:
                  rel_iter.populate(row, obj)
          self.local_setter(from_obj, obj)
          if obj is not None:
              self.remote_setter(obj, from_obj)
  
  
  def get_related_populators(klass_info, select, db):
      iterators = []
      related_klass_infos = klass_info.get("related_klass_infos", [])
      for rel_klass_info in related_klass_infos:
          rel_cls = RelatedPopulator(rel_klass_info, select, db)
          iterators.append(rel_cls)
      return iterators
  