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Diffstat (limited to 'webapp/django/db/models/query.py')
| -rw-r--r-- | webapp/django/db/models/query.py | 884 |
1 files changed, 884 insertions, 0 deletions
diff --git a/webapp/django/db/models/query.py b/webapp/django/db/models/query.py new file mode 100644 index 0000000000..2ff1c26344 --- /dev/null +++ b/webapp/django/db/models/query.py @@ -0,0 +1,884 @@ +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() + 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() + 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. + return None, index_end + 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 + 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) |