django1/django/db/models/query.py

887 lines
31 KiB
Python

try:
set
except NameError:
from sets import Set as set # Python 2.3 fallback
from django.db import connection, transaction, IntegrityError
from django.db.models.fields import DateField
from django.db.models.query_utils import Q, select_related_descend
from django.db.models import signals, sql
from django.utils.datastructures import SortedDict
# Used to control how many objects are worked with at once in some cases (e.g.
# when deleting objects).
CHUNK_SIZE = 100
ITER_CHUNK_SIZE = CHUNK_SIZE
# Pull into this namespace for backwards compatibility.
EmptyResultSet = sql.EmptyResultSet
class CyclicDependency(Exception):
"""
An error when dealing with a collection of objects that have a cyclic
dependency, i.e. when deleting multiple objects.
"""
pass
class CollectedObjects(object):
"""
A container that stores keys and lists of values along with remembering the
parent objects for all the keys.
This is used for the database object deletion routines so that we can
calculate the 'leaf' objects which should be deleted first.
"""
def __init__(self):
self.data = {}
self.children = {}
def add(self, model, pk, obj, parent_model, nullable=False):
"""
Adds an item to the container.
Arguments:
* model - the class of the object being added.
* pk - the primary key.
* obj - the object itself.
* parent_model - the model of the parent object that this object was
reached through.
* nullable - should be True if this relation is nullable.
Returns True if the item already existed in the structure and
False otherwise.
"""
d = self.data.setdefault(model, SortedDict())
retval = pk in d
d[pk] = obj
# Nullable relationships can be ignored -- they are nulled out before
# deleting, and therefore do not affect the order in which objects
# have to be deleted.
if parent_model is not None and not nullable:
self.children.setdefault(parent_model, []).append(model)
return retval
def __contains__(self, key):
return self.data.__contains__(key)
def __getitem__(self, key):
return self.data[key]
def __nonzero__(self):
return bool(self.data)
def iteritems(self):
for k in self.ordered_keys():
yield k, self[k]
def items(self):
return list(self.iteritems())
def keys(self):
return self.ordered_keys()
def ordered_keys(self):
"""
Returns the models in the order that they should be dealt with (i.e.
models with no dependencies first).
"""
dealt_with = SortedDict()
# Start with items that have no children
models = self.data.keys()
while len(dealt_with) < len(models):
found = False
for model in models:
children = self.children.setdefault(model, [])
if len([c for c in children if c not in dealt_with]) == 0:
dealt_with[model] = None
found = True
if not found:
raise CyclicDependency(
"There is a cyclic dependency of items to be processed.")
return dealt_with.keys()
def unordered_keys(self):
"""
Fallback for the case where is a cyclic dependency but we don't care.
"""
return self.data.keys()
class QuerySet(object):
"""
Represents a lazy database lookup for a set of objects.
"""
def __init__(self, model=None, query=None):
self.model = model
self.query = query or sql.Query(self.model, connection)
self._result_cache = None
self._iter = None
self._sticky_filter = False
########################
# PYTHON MAGIC METHODS #
########################
def __getstate__(self):
"""
Allows the QuerySet to be pickled.
"""
# Force the cache to be fully populated.
len(self)
obj_dict = self.__dict__.copy()
obj_dict['_iter'] = None
return obj_dict
def __repr__(self):
return repr(list(self))
def __len__(self):
# Since __len__ is called quite frequently (for example, as part of
# list(qs), we make some effort here to be as efficient as possible
# whilst not messing up any existing iterators against the QuerySet.
if self._result_cache is None:
if self._iter:
self._result_cache = list(self._iter)
else:
self._result_cache = list(self.iterator())
elif self._iter:
self._result_cache.extend(list(self._iter))
return len(self._result_cache)
def __iter__(self):
if self._result_cache is None:
self._iter = self.iterator()
self._result_cache = []
if self._iter:
return self._result_iter()
# Python's list iterator is better than our version when we're just
# iterating over the cache.
return iter(self._result_cache)
def _result_iter(self):
pos = 0
while 1:
upper = len(self._result_cache)
while pos < upper:
yield self._result_cache[pos]
pos = pos + 1
if not self._iter:
raise StopIteration
if len(self._result_cache) <= pos:
self._fill_cache()
def __nonzero__(self):
if self._result_cache is not None:
return bool(self._result_cache)
try:
iter(self).next()
except StopIteration:
return False
return True
def __getitem__(self, k):
"""
Retrieves an item or slice from the set of results.
"""
if not isinstance(k, (slice, int, long)):
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:
if self._iter is not None:
# The result cache has only been partially populated, so we may
# need to fill it out a bit more.
if isinstance(k, slice):
if k.stop is not None:
# Some people insist on passing in strings here.
bound = int(k.stop)
else:
bound = None
else:
bound = k + 1
if len(self._result_cache) < bound:
self._fill_cache(bound - len(self._result_cache))
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 k.step and list(qs)[::k.step] or qs
try:
qs = self._clone()
qs.query.set_limits(k, k + 1)
return list(qs)[0]
except self.model.DoesNotExist, e:
raise IndexError, e.args
def __and__(self, other):
self._merge_sanity_check(other)
if isinstance(other, EmptyQuerySet):
return other._clone()
combined = self._clone()
combined.query.combine(other.query, sql.AND)
return combined
def __or__(self, other):
self._merge_sanity_check(other)
combined = self._clone()
if isinstance(other, EmptyQuerySet):
return combined
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 = self.query.select_related
if isinstance(fill_cache, dict):
requested = fill_cache
else:
requested = None
max_depth = self.query.max_depth
extra_select = self.query.extra_select.keys()
index_start = len(extra_select)
for row in self.query.results_iter():
if fill_cache:
obj, _ = get_cached_row(self.model, row, index_start,
max_depth, requested=requested)
else:
obj = self.model(*row[index_start:])
for i, k in enumerate(extra_select):
setattr(obj, k, row[i])
yield obj
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 and not self._iter:
return len(self._result_cache)
return self.query.get_count()
def get(self, *args, **kwargs):
"""
Performs the query and returns a single object matching the given
keyword arguments.
"""
clone = self.filter(*args, **kwargs)
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! Lookup parameters were %s"
% (self.model._meta.object_name, num, kwargs))
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)
obj.save(force_insert=True)
return obj
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.
"""
assert kwargs, \
'get_or_create() must be passed at least one keyword argument'
defaults = kwargs.pop('defaults', {})
try:
return self.get(**kwargs), False
except self.model.DoesNotExist:
try:
params = dict([(k, v) for k, v in kwargs.items() if '__' not in k])
params.update(defaults)
obj = self.model(**params)
sid = transaction.savepoint()
obj.save(force_insert=True)
transaction.savepoint_commit(sid)
return obj, True
except IntegrityError, e:
transaction.savepoint_rollback(sid)
try:
return self.get(**kwargs), False
except self.model.DoesNotExist:
raise e
def latest(self, field_name=None):
"""
Returns the latest object, according to the model's 'get_latest_by'
option or optional given field_name.
"""
latest_by = field_name or self.model._meta.get_latest_by
assert bool(latest_by), "latest() requires 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.add_ordering('-%s' % latest_by)
return obj.get()
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"
assert isinstance(id_list, (tuple, list)), \
"in_bulk() must be provided with a list of IDs."
if not id_list:
return {}
qs = self._clone()
qs.query.add_filter(('pk__in', id_list))
return dict([(obj._get_pk_val(), obj) for obj in qs.iterator()])
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()
# Disable non-supported fields.
del_query.query.select_related = False
del_query.query.clear_ordering()
# Delete objects in chunks to prevent the list of related objects from
# becoming too long.
while 1:
# Collect all the objects to be deleted in this chunk, and all the
# objects that are related to the objects that are to be deleted.
seen_objs = CollectedObjects()
for object in del_query[:CHUNK_SIZE]:
object._collect_sub_objects(seen_objs)
if not seen_objs:
break
delete_objects(seen_objs)
# Clear the result cache, in case this QuerySet gets reused.
self._result_cache = None
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."
query = self.query.clone(sql.UpdateQuery)
query.add_update_values(kwargs)
rows = query.execute_sql(None)
transaction.commit_unless_managed()
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.execute_sql(None)
_update.alters_data = 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'
% (kwargs.keys(),))
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 datetime objects representing all available dates for
the given field_name, scoped to 'kind'.
"""
assert kind in ("month", "year", "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 none(self):
"""
Returns an empty QuerySet.
"""
return self._clone(klass=EmptyQuerySet)
##################################################################
# 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_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.
"""
depth = kwargs.pop('depth', 0)
if kwargs:
raise TypeError('Unexpected keyword arguments to select_related: %s'
% (kwargs.keys(),))
obj = self._clone()
if 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 dup_select_related(self, other):
"""
Copies the related selection status from the QuerySet 'other' to the
current QuerySet.
"""
self.query.select_related = other.query.select_related
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()
obj.query.add_ordering(*field_names)
return obj
def distinct(self, true_or_false=True):
"""
Returns a new QuerySet instance that will select only distinct results.
"""
obj = self._clone()
obj.query.distinct = true_or_false
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
###################
# PRIVATE METHODS #
###################
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)
c.__dict__.update(kwargs)
if setup and hasattr(c, '_setup_query'):
c._setup_query()
return c
def _fill_cache(self, num=None):
"""
Fills the result cache with 'num' more entries (or until the results
iterator is exhausted).
"""
if self._iter:
try:
for i in range(num or ITER_CHUNK_SIZE):
self._result_cache.append(self._iter.next())
except StopIteration:
self._iter = None
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
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):
if (not self.extra_names and
len(self.field_names) != len(self.model._meta.fields)):
self.query.trim_extra_select(self.extra_names)
names = self.query.extra_select.keys() + self.field_names
for row in self.query.results_iter():
yield dict(zip(names, row))
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.extra_names = []
if self._fields:
if not self.query.extra_select:
field_names = list(self._fields)
else:
field_names = []
for f in self._fields:
if self.query.extra_select.has_key(f):
self.extra_names.append(f)
else:
field_names.append(f)
else:
# Default to all fields.
field_names = [f.attname for f in self.model._meta.fields]
self.query.add_fields(field_names, False)
self.query.default_cols = False
self.field_names = field_names
def _clone(self, klass=None, setup=False, **kwargs):
"""
Cloning a ValuesQuerySet preserves the current fields.
"""
c = super(ValuesQuerySet, self)._clone(klass, **kwargs)
c._fields = self._fields[:]
c.field_names = self.field_names
c.extra_names = self.extra_names
if setup and hasattr(c, '_setup_query'):
c._setup_query()
return c
def _merge_sanity_check(self, other):
super(ValuesQuerySet, self)._merge_sanity_check(other)
if (set(self.extra_names) != set(other.extra_names) or
set(self.field_names) != set(other.field_names)):
raise TypeError("Merging '%s' classes must involve the same values in each case."
% self.__class__.__name__)
class ValuesListQuerySet(ValuesQuerySet):
def iterator(self):
self.query.trim_extra_select(self.extra_names)
if self.flat and len(self._fields) == 1:
for row in self.query.results_iter():
yield row[0]
elif not self.query.extra_select:
for row in self.query.results_iter():
yield tuple(row)
else:
# When extra(select=...) is involved, the extra cols come are
# always at the start of the row, so we need to reorder the fields
# to match the order in self._fields.
names = self.query.extra_select.keys() + self.field_names
for row in self.query.results_iter():
data = dict(zip(names, row))
yield tuple([data[f] for f in self._fields])
def _clone(self, *args, **kwargs):
clone = super(ValuesListQuerySet, self)._clone(*args, **kwargs)
clone.flat = self.flat
return clone
class DateQuerySet(QuerySet):
def iterator(self):
return self.query.results_iter()
def _setup_query(self):
"""
Sets up any special features of the query attribute.
Called by the _clone() method after initializing the rest of the
instance.
"""
self.query = self.query.clone(klass=sql.DateQuery, setup=True)
self.query.select = []
field = self.model._meta.get_field(self._field_name, many_to_many=False)
assert isinstance(field, DateField), "%r isn't a DateField." \
% field.name
self.query.add_date_select(field, self._kind, self._order)
if field.null:
self.query.add_filter(('%s__isnull' % field.name, False))
def _clone(self, klass=None, setup=False, **kwargs):
c = super(DateQuerySet, self)._clone(klass, False, **kwargs)
c._field_name = self._field_name
c._kind = self._kind
if setup and hasattr(c, '_setup_query'):
c._setup_query()
return c
class EmptyQuerySet(QuerySet):
def __init__(self, model=None, query=None):
super(EmptyQuerySet, self).__init__(model, query)
self._result_cache = []
def __and__(self, other):
return self._clone()
def __or__(self, other):
return other._clone()
def count(self):
return 0
def delete(self):
pass
def _clone(self, klass=None, setup=False, **kwargs):
c = super(EmptyQuerySet, self)._clone(klass, **kwargs)
c._result_cache = []
return c
def iterator(self):
# This slightly odd construction is because we need an empty generator
# (it raises StopIteration immediately).
yield iter([]).next()
def get_cached_row(klass, row, index_start, max_depth=0, cur_depth=0,
requested=None):
"""
Helper function that recursively returns an object with the specified
related attributes already populated.
"""
if max_depth and requested is None and cur_depth > max_depth:
# We've recursed deeply enough; stop now.
return None
restricted = requested is not None
index_end = index_start + len(klass._meta.fields)
fields = row[index_start:index_end]
if not [x for x in fields if x is not None]:
# If we only have a list of Nones, there was not related object.
obj = None
else:
obj = klass(*fields)
for f in klass._meta.fields:
if not select_related_descend(f, restricted, requested):
continue
if restricted:
next = requested[f.name]
else:
next = None
cached_row = get_cached_row(f.rel.to, row, index_end, max_depth,
cur_depth+1, next)
if cached_row:
rel_obj, index_end = cached_row
if obj is not None:
setattr(obj, f.get_cache_name(), rel_obj)
return obj, index_end
def delete_objects(seen_objs):
"""
Iterate through a list of seen classes, and remove any instances that are
referred to.
"""
try:
ordered_classes = seen_objs.keys()
except CyclicDependency:
# If there is a cyclic dependency, we cannot in general delete the
# objects. However, if an appropriate transaction is set up, or if the
# database is lax enough, it will succeed. So for now, we go ahead and
# try anyway.
ordered_classes = seen_objs.unordered_keys()
obj_pairs = {}
for cls in ordered_classes:
items = seen_objs[cls].items()
items.sort()
obj_pairs[cls] = items
# Pre-notify all instances to be deleted.
for pk_val, instance in items:
signals.pre_delete.send(sender=cls, instance=instance)
pk_list = [pk for pk,instance in items]
del_query = sql.DeleteQuery(cls, connection)
del_query.delete_batch_related(pk_list)
update_query = sql.UpdateQuery(cls, connection)
for field, model in cls._meta.get_fields_with_model():
if (field.rel and field.null and field.rel.to in seen_objs and
filter(lambda f: f.column == field.column,
field.rel.to._meta.fields)):
if model:
sql.UpdateQuery(model, connection).clear_related(field,
pk_list)
else:
update_query.clear_related(field, pk_list)
# Now delete the actual data.
for cls in ordered_classes:
items = obj_pairs[cls]
items.reverse()
pk_list = [pk for pk,instance in items]
del_query = sql.DeleteQuery(cls, connection)
del_query.delete_batch(pk_list)
# Last cleanup; set NULLs where there once was a reference to the
# object, NULL the primary key of the found objects, and perform
# post-notification.
for pk_val, instance in items:
for field in cls._meta.fields:
if field.rel and field.null and field.rel.to in seen_objs:
setattr(instance, field.attname, None)
signals.post_delete.send(sender=cls, instance=instance)
setattr(instance, cls._meta.pk.attname, None)
transaction.commit_unless_managed()
def insert_query(model, values, return_id=False, raw_values=False):
"""
Inserts a new record for the given model. This provides an interface to
the InsertQuery class and is how Model.save() is implemented. It is not
part of the public API.
"""
query = sql.InsertQuery(model, connection)
query.insert_values(values, raw_values)
return query.execute_sql(return_id)