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query.py
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query.py
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"""
The main QuerySet implementation. This provides the public API for the ORM.
"""
import copy
import itertools
import sys
import warnings
from django.conf import settings
from django.core import exceptions
from django.db import connections, router, transaction, DatabaseError
from django.db.models.constants import LOOKUP_SEP
from django.db.models.fields import AutoField
from django.db.models.query_utils import (Q, select_related_descend,
deferred_class_factory, InvalidQuery)
from django.db.models.deletion import Collector
from django.db.models import sql
from django.utils.functional import partition
from django.utils import six
from django.utils import timezone
# The maximum number of items to display in a QuerySet.__repr__
REPR_OUTPUT_SIZE = 20
# Pull into this namespace for backwards compatibility.
EmptyResultSet = sql.EmptyResultSet
class QuerySet(object):
"""
Represents a lazy database lookup for a set of objects.
"""
def __init__(self, model=None, query=None, using=None):
self.model = model
self._db = using
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}}
########################
# PYTHON MAGIC METHODS #
########################
def __deepcopy__(self, memo):
"""
Deep copy of a QuerySet doesn't populate the 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):
"""
Allows the QuerySet to be pickled.
"""
# Force the cache to be fully populated.
self._fetch_all()
obj_dict = self.__dict__.copy()
return obj_dict
def __repr__(self):
data = list(self[:REPR_OUTPUT_SIZE + 1])
if len(data) > REPR_OUTPUT_SIZE:
data[-1] = "...(remaining elements truncated)..."
return repr(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 (see resolve_columns(),
resolve_aggregate()).
3. self.iterator()
- Responsible for turning the rows into model objects.
"""
self._fetch_all()
return iter(self._result_cache)
def __nonzero__(self):
self._fetch_all()
return bool(self._result_cache)
def __getitem__(self, k):
"""
Retrieves an item or slice from the set of results.
"""
if not isinstance(k, (slice,) + six.integer_types):
raise TypeError
assert ((not isinstance(k, slice) and (k >= 0))
or (isinstance(k, slice) and (k.start is None or k.start >= 0)
and (k.stop is None or k.stop >= 0))), \
"Negative indexing is not supported."
if self._result_cache is not None:
return self._result_cache[k]
if isinstance(k, slice):
qs = self._clone()
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._clone()
qs.query.set_limits(k, k + 1)
return list(qs)[0]
def __and__(self, other):
self._merge_sanity_check(other)
if isinstance(other, EmptyQuerySet):
return other
if isinstance(self, EmptyQuerySet):
return self
combined = self._clone()
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
combined = self._clone()
combined._merge_known_related_objects(other)
combined.query.combine(other.query, sql.OR)
return combined
####################################
# METHODS THAT DO DATABASE QUERIES #
####################################
def iterator(self):
"""
An iterator over the results from applying this QuerySet to the
database.
"""
fill_cache = False
if connections[self.db].features.supports_select_related:
fill_cache = self.query.select_related
if isinstance(fill_cache, dict):
requested = fill_cache
else:
requested = None
max_depth = self.query.max_depth
extra_select = list(self.query.extra_select)
aggregate_select = list(self.query.aggregate_select)
only_load = self.query.get_loaded_field_names()
if not fill_cache:
fields = self.model._meta.concrete_fields
load_fields = []
# If only/defer clauses have been specified,
# build the list of fields that are to be loaded.
if only_load:
for field, model in self.model._meta.get_concrete_fields_with_model():
if model is None:
model = self.model
try:
if field.name in only_load[model]:
# Add a field that has been explicitly included
load_fields.append(field.name)
except KeyError:
# Model wasn't explicitly listed in the only_load table
# Therefore, we need to load all fields from this model
load_fields.append(field.name)
index_start = len(extra_select)
aggregate_start = index_start + len(load_fields or self.model._meta.concrete_fields)
skip = None
if load_fields and not fill_cache:
# Some fields have been deferred, so we have to initialise
# via keyword arguments.
skip = set()
init_list = []
for field in fields:
if field.name not in load_fields:
skip.add(field.attname)
else:
init_list.append(field.attname)
model_cls = deferred_class_factory(self.model, skip)
# Cache db and model outside the loop
db = self.db
model = self.model
compiler = self.query.get_compiler(using=db)
if fill_cache:
klass_info = get_klass_info(model, max_depth=max_depth,
requested=requested, only_load=only_load)
for row in compiler.results_iter():
if fill_cache:
obj, _ = get_cached_row(row, index_start, db, klass_info,
offset=len(aggregate_select))
else:
# Omit aggregates in object creation.
row_data = row[index_start:aggregate_start]
if skip:
obj = model_cls(**dict(zip(init_list, row_data)))
else:
obj = model(*row_data)
# Store the source database of the object
obj._state.db = db
# This object came from the database; it's not being added.
obj._state.adding = False
if extra_select:
for i, k in enumerate(extra_select):
setattr(obj, k, row[i])
# Add the aggregates to the model
if aggregate_select:
for i, aggregate in enumerate(aggregate_select):
setattr(obj, aggregate, row[i + aggregate_start])
# Add the known related objects to the model, if there are any
if self._known_related_objects:
for field, rel_objs in self._known_related_objects.items():
# Avoid overwriting objects loaded e.g. by select_related
if hasattr(obj, field.get_cache_name()):
continue
pk = getattr(obj, field.get_attname())
try:
rel_obj = rel_objs[pk]
except KeyError:
pass # may happen in qs1 | qs2 scenarios
else:
setattr(obj, field.name, rel_obj)
yield obj
def aggregate(self, *args, **kwargs):
"""
Returns 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.")
for arg in args:
kwargs[arg.default_alias] = arg
query = self.query.clone()
for (alias, aggregate_expr) in kwargs.items():
query.add_aggregate(aggregate_expr, self.model, alias,
is_summary=True)
return query.get_aggregation(using=self.db)
def count(self):
"""
Performs a SELECT COUNT() and returns the number of records as an
integer.
If the QuerySet is already fully cached this simply returns 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):
"""
Performs the query and returns a single object matching the given
keyword arguments.
"""
clone = self.filter(*args, **kwargs)
if self.query.can_filter():
clone = clone.order_by()
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))
def create(self, **kwargs):
"""
Creates 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 bulk_create(self, objs, batch_size=None):
"""
Inserts each of the instances into the database. This does *not* call
save() on each of the instances, does not send any pre/post save
signals, and does not set the primary key attribute if it is an
autoincrement field.
"""
# So this case is fun. When you bulk insert you don't get the primary
# keys back (if it's an autoincrement), 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,
# and 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. Some databases might allow doing
# this by using RETURNING clause for the insert query. We're punting
# on these for now because they are relatively rare cases.
assert batch_size is None or batch_size > 0
if self.model._meta.parents:
raise ValueError("Can't bulk create an inherited model")
if not objs:
return objs
self._for_write = True
connection = connections[self.db]
fields = self.model._meta.local_concrete_fields
with transaction.commit_on_success_unless_managed(using=self.db):
if (connection.features.can_combine_inserts_with_and_without_auto_increment_pk
and self.model._meta.has_auto_field):
self._batched_insert(objs, fields, batch_size)
else:
objs_with_pk, objs_without_pk = partition(lambda o: o.pk is None, objs)
if objs_with_pk:
self._batched_insert(objs_with_pk, fields, batch_size)
if objs_without_pk:
fields= [f for f in fields if not isinstance(f, AutoField)]
self._batched_insert(objs_without_pk, fields, batch_size)
return objs
def get_or_create(self, **kwargs):
"""
Looks up an object with the given kwargs, creating one if necessary.
Returns a tuple of (object, created), where created is a boolean
specifying whether an object was created.
"""
defaults = kwargs.pop('defaults', {})
lookup = kwargs.copy()
for f in self.model._meta.fields:
if f.attname in lookup:
lookup[f.name] = lookup.pop(f.attname)
try:
self._for_write = True
return self.get(**lookup), False
except self.model.DoesNotExist:
try:
params = dict((k, v) for k, v in kwargs.items() if LOOKUP_SEP not in k)
params.update(defaults)
obj = self.model(**params)
with transaction.atomic(using=self.db):
obj.save(force_insert=True, using=self.db)
return obj, True
except DatabaseError:
exc_info = sys.exc_info()
try:
return self.get(**lookup), False
except self.model.DoesNotExist:
# Re-raise the DatabaseError with its original traceback.
six.reraise(*exc_info)
def _earliest_or_latest(self, field_name=None, direction="-"):
"""
Returns the latest object, according to the model's
'get_latest_by' option or optional given field_name.
"""
order_by = field_name or getattr(self.model._meta, 'get_latest_by')
assert bool(order_by), "earliest() and latest() require either a "\
"field_name parameter or 'get_latest_by' in the model"
assert self.query.can_filter(), \
"Cannot change a query once a slice has been taken."
obj = self._clone()
obj.query.set_limits(high=1)
obj.query.clear_ordering(force_empty=True)
obj.query.add_ordering('%s%s' % (direction, order_by))
return obj.get()
def earliest(self, field_name=None):
return self._earliest_or_latest(field_name=field_name, direction="")
def latest(self, field_name=None):
return self._earliest_or_latest(field_name=field_name, direction="-")
def first(self):
"""
Returns the first object of a query, returns None if no match is found.
"""
qs = self if self.ordered else self.order_by('pk')
try:
return qs[0]
except IndexError:
return None
def last(self):
"""
Returns the last object of a query, returns None if no match is found.
"""
qs = self.reverse() if self.ordered else self.order_by('-pk')
try:
return qs[0]
except IndexError:
return None
def in_bulk(self, id_list):
"""
Returns a dictionary mapping each of the given IDs to the object with
that ID.
"""
assert self.query.can_filter(), \
"Cannot use 'limit' or 'offset' with in_bulk"
if not id_list:
return {}
qs = self.filter(pk__in=id_list).order_by()
return dict([(obj._get_pk_val(), obj) for obj in qs])
def delete(self):
"""
Deletes the records in the current QuerySet.
"""
assert self.query.can_filter(), \
"Cannot use 'limit' or 'offset' with delete."
del_query = self._clone()
# 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_empty=True)
collector = Collector(using=del_query.db)
collector.collect(del_query)
collector.delete()
# Clear the result cache, in case this QuerySet gets reused.
self._result_cache = None
delete.alters_data = True
def _raw_delete(self, using):
"""
Deletes objects found from the given queryset in single direct SQL
query. No signals are sent, and there is no protection for cascades.
"""
sql.DeleteQuery(self.model).delete_qs(self, using)
_raw_delete.alters_data = True
def update(self, **kwargs):
"""
Updates all elements in the current QuerySet, setting all the given
fields to the appropriate values.
"""
assert self.query.can_filter(), \
"Cannot update a query once a slice has been taken."
self._for_write = True
query = self.query.clone(sql.UpdateQuery)
query.add_update_values(kwargs)
with transaction.commit_on_success_unless_managed(using=self.db):
rows = query.get_compiler(self.db).execute_sql(None)
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).
"""
assert self.query.can_filter(), \
"Cannot update a query once a slice has been taken."
query = self.query.clone(sql.UpdateQuery)
query.add_update_fields(values)
self._result_cache = None
return query.get_compiler(self.db).execute_sql(None)
_update.alters_data = True
def exists(self):
if self._result_cache is None:
return self.query.has_results(using=self.db)
return bool(self._result_cache)
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
##################################################
# PUBLIC METHODS THAT RETURN A QUERYSET SUBCLASS #
##################################################
def values(self, *fields):
return self._clone(klass=ValuesQuerySet, setup=True, _fields=fields)
def values_list(self, *fields, **kwargs):
flat = kwargs.pop('flat', False)
if kwargs:
raise TypeError('Unexpected keyword arguments to values_list: %s'
% (list(kwargs),))
if flat and len(fields) > 1:
raise TypeError("'flat' is not valid when values_list is called with more than one field.")
return self._clone(klass=ValuesListQuerySet, setup=True, flat=flat,
_fields=fields)
def dates(self, field_name, kind, order='ASC'):
"""
Returns a list of date objects representing all available dates for
the given field_name, scoped to 'kind'.
"""
assert kind in ("year", "month", "day"), \
"'kind' must be one of 'year', 'month' or 'day'."
assert order in ('ASC', 'DESC'), \
"'order' must be either 'ASC' or 'DESC'."
return self._clone(klass=DateQuerySet, setup=True,
_field_name=field_name, _kind=kind, _order=order)
def datetimes(self, field_name, kind, order='ASC', tzinfo=None):
"""
Returns a list of datetime objects representing all available
datetimes for the given field_name, scoped to 'kind'.
"""
assert kind in ("year", "month", "day", "hour", "minute", "second"), \
"'kind' must be one of 'year', 'month', 'day', 'hour', 'minute' or 'second'."
assert order in ('ASC', 'DESC'), \
"'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._clone(klass=DateTimeQuerySet, setup=True,
_field_name=field_name, _kind=kind, _order=order, _tzinfo=tzinfo)
def none(self):
"""
Returns an empty QuerySet.
"""
clone = self._clone()
clone.query.set_empty()
return clone
##################################################################
# PUBLIC METHODS THAT ALTER ATTRIBUTES AND RETURN A NEW QUERYSET #
##################################################################
def all(self):
"""
Returns 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._clone()
def filter(self, *args, **kwargs):
"""
Returns a new QuerySet instance with the args ANDed to the existing
set.
"""
return self._filter_or_exclude(False, *args, **kwargs)
def exclude(self, *args, **kwargs):
"""
Returns a new QuerySet instance with NOT (args) ANDed to the existing
set.
"""
return self._filter_or_exclude(True, *args, **kwargs)
def _filter_or_exclude(self, negate, *args, **kwargs):
if args or kwargs:
assert self.query.can_filter(), \
"Cannot filter a query once a slice has been taken."
clone = self._clone()
if negate:
clone.query.add_q(~Q(*args, **kwargs))
else:
clone.query.add_q(Q(*args, **kwargs))
return clone
def complex_filter(self, filter_obj):
"""
Returns a new QuerySet instance with filter_obj added to the filters.
filter_obj can be a Q object (or anything with an add_to_query()
method) 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) or hasattr(filter_obj, 'add_to_query'):
clone = self._clone()
clone.query.add_q(filter_obj)
return clone
else:
return self._filter_or_exclude(None, **filter_obj)
def select_for_update(self, **kwargs):
"""
Returns a new QuerySet instance that will select objects with a
FOR UPDATE lock.
"""
# Default to false for nowait
nowait = kwargs.pop('nowait', False)
obj = self._clone()
obj._for_write = True
obj.query.select_for_update = True
obj.query.select_for_update_nowait = nowait
return obj
def select_related(self, *fields, **kwargs):
"""
Returns 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, the list is cleared.
"""
if 'depth' in kwargs:
warnings.warn('The "depth" keyword argument has been deprecated.\n'
'Use related field names instead.', DeprecationWarning, stacklevel=2)
depth = kwargs.pop('depth', 0)
if kwargs:
raise TypeError('Unexpected keyword arguments to select_related: %s'
% (list(kwargs),))
obj = self._clone()
if fields == (None,):
obj.query.select_related = False
elif fields:
if depth:
raise TypeError('Cannot pass both "depth" and fields to select_related()')
obj.query.add_select_related(fields)
else:
obj.query.select_related = True
if depth:
obj.query.max_depth = depth
return obj
def prefetch_related(self, *lookups):
"""
Returns 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, the list of lookups to
prefetch is appended to. If prefetch_related(None) is called, the
the list is cleared.
"""
clone = self._clone()
if lookups == (None,):
clone._prefetch_related_lookups = []
else:
clone._prefetch_related_lookups.extend(lookups)
return clone
def annotate(self, *args, **kwargs):
"""
Return a query set in which the returned objects have been annotated
with data aggregated from related fields.
"""
for arg in args:
if arg.default_alias in kwargs:
raise ValueError("The named annotation '%s' conflicts with the "
"default name for another annotation."
% arg.default_alias)
kwargs[arg.default_alias] = arg
names = getattr(self, '_fields', None)
if names is None:
names = set(self.model._meta.get_all_field_names())
for aggregate in kwargs:
if aggregate in names:
raise ValueError("The annotation '%s' conflicts with a field on "
"the model." % aggregate)
obj = self._clone()
obj._setup_aggregate_query(list(kwargs))
# Add the aggregates to the query
for (alias, aggregate_expr) in kwargs.items():
obj.query.add_aggregate(aggregate_expr, self.model, alias,
is_summary=False)
return obj
def order_by(self, *field_names):
"""
Returns a new QuerySet instance with the ordering changed.
"""
assert self.query.can_filter(), \
"Cannot reorder a query once a slice has been taken."
obj = self._clone()
obj.query.clear_ordering(force_empty=False)
obj.query.add_ordering(*field_names)
return obj
def distinct(self, *field_names):
"""
Returns a new QuerySet instance that will select only distinct results.
"""
assert self.query.can_filter(), \
"Cannot create distinct fields once a slice has been taken."
obj = self._clone()
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):
"""
Adds extra SQL fragments to the query.
"""
assert self.query.can_filter(), \
"Cannot change a query once a slice has been taken"
clone = self._clone()
clone.query.add_extra(select, select_params, where, params, tables, order_by)
return clone
def reverse(self):
"""
Reverses the ordering of the QuerySet.
"""
clone = self._clone()
clone.query.standard_ordering = not clone.query.standard_ordering
return clone
def defer(self, *fields):
"""
Defers the loading of data for certain fields until they are accessed.
The set of fields to defer is added 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 all deferrals are removed (None acts as a
reset option).
"""
clone = self._clone()
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.
"""
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().")
clone = self._clone()
clone.query.add_immediate_loading(fields)
return clone
def using(self, alias):
"""
Selects which database this QuerySet should excecute its query against.
"""
clone = self._clone()
clone._db = alias
return clone
###################################
# PUBLIC INTROSPECTION ATTRIBUTES #
###################################
def ordered(self):
"""
Returns True if the QuerySet is ordered -- i.e. has an order_by()
clause or a default ordering on the model.
"""
if self.query.extra_order_by or self.query.order_by:
return True
elif self.query.default_ordering and self.query.get_meta().ordering:
return True
else:
return False
ordered = property(ordered)
@property
def db(self):
"Return the database that will be used if this query is executed now"
if self._for_write:
return self._db or router.db_for_write(self.model)
return self._db or router.db_for_read(self.model)
###################
# PRIVATE METHODS #
###################
def _batched_insert(self, objs, fields, batch_size):
"""
A little helper method for bulk_insert to insert the bulk one batch
at a time. Inserts recursively a batch from the front of the bulk and
then _batched_insert() the remaining objects again.
"""
if not objs:
return
ops = connections[self.db].ops
batch_size = (batch_size or max(ops.bulk_batch_size(fields, objs), 1))
for batch in [objs[i:i+batch_size]
for i in range(0, len(objs), batch_size)]:
self.model._base_manager._insert(batch, fields=fields,
using=self.db)
def _clone(self, klass=None, setup=False, **kwargs):
if klass is None:
klass = self.__class__
query = self.query.clone()
if self._sticky_filter:
query.filter_is_sticky = True
c = klass(model=self.model, query=query, using=self._db)
c._for_write = self._for_write
c._prefetch_related_lookups = self._prefetch_related_lookups[:]
c._known_related_objects = self._known_related_objects
c.__dict__.update(kwargs)
if setup and hasattr(c, '_setup_query'):
c._setup_query()
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 _next_is_sticky(self):
"""
Indicates 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):
"""
Checks that we are merging two comparable QuerySet classes. By default
this does nothing, but see the ValuesQuerySet for an example of where
it's useful.
"""
pass
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 _setup_aggregate_query(self, aggregates):
"""
Prepare the query for computing a result that contains aggregate annotations.
"""
opts = self.model._meta
if self.query.group_by is None:
field_names = [f.attname for f in opts.concrete_fields]
self.query.add_fields(field_names, False)
self.query.set_group_by()
def _prepare(self):
return self
def _as_sql(self, connection):
"""
Returns the internal query's SQL and parameters (as a tuple).
"""
obj = self.values("pk")
if obj._db is None or connection == connections[obj._db]:
return obj.query.get_compiler(connection=connection).as_nested_sql()
raise ValueError("Can't do subqueries with queries on different DBs.")
# When used as part of a nested query, a queryset will never be an "always
# empty" result.
value_annotation = True
class InstanceCheckMeta(type):
def __instancecheck__(self, instance):
return instance.query.is_empty()
class EmptyQuerySet(six.with_metaclass(InstanceCheckMeta)):
"""
Marker class usable for 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 ValuesQuerySet(QuerySet):
def __init__(self, *args, **kwargs):
super(ValuesQuerySet, self).__init__(*args, **kwargs)
# select_related isn't supported in values(). (FIXME -#3358)
self.query.select_related = False
# QuerySet.clone() will also set up the _fields attribute with the
# names of the model fields to select.
def iterator(self):
# Purge any extra columns that haven't been explicitly asked for
extra_names = list(self.query.extra_select)
field_names = self.field_names
aggregate_names = list(self.query.aggregate_select)
names = extra_names + field_names + aggregate_names
for row in self.query.get_compiler(self.db).results_iter():
yield dict(zip(names, row))
def delete(self):
# values().delete() doesn't work currently - make sure it raises an
# user friendly error.
raise TypeError("Queries with .values() or .values_list() applied "
"can't be deleted")
def _setup_query(self):
"""
Constructs the field_names list that the values query will be
retrieving.
Called by the _clone() method after initializing the rest of the
instance.
"""
self.query.clear_deferred_loading()
self.query.clear_select_fields()
if self._fields:
self.extra_names = []
self.aggregate_names = []
if not self.query.extra and not self.query.aggregates:
# Short cut - if there are no extra or aggregates, then
# the values() clause must be just field names.
self.field_names = list(self._fields)
else:
self.query.default_cols = False
self.field_names = []
for f in self._fields:
# we inspect the full extra_select list since we might
# be adding back an extra select item that we hadn't
# had selected previously.
if f in self.query.extra:
self.extra_names.append(f)
elif f in self.query.aggregate_select:
self.aggregate_names.append(f)
else:
self.field_names.append(f)
else:
# Default to all fields.
self.extra_names = None
self.field_names = [f.attname for f in self.model._meta.concrete_fields]
self.aggregate_names = None
self.query.select = []
if self.extra_names is not None:
self.query.set_extra_mask(self.extra_names)
self.query.add_fields(self.field_names, True)
if self.aggregate_names is not None:
self.query.set_aggregate_mask(self.aggregate_names)
def _clone(self, klass=None, setup=False, **kwargs):
"""