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07ddd56872
git-svn-id: http://code.djangoproject.com/svn/django/branches/queryset-refactor@6857 bcc190cf-cafb-0310-a4f2-bffc1f526a37
557 lines
20 KiB
Python
557 lines
20 KiB
Python
import datetime
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import operator
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import re
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import warnings
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from django.conf import settings
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from django.db import connection, transaction
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from django.db.models.fields import DateField, FieldDoesNotExist
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from django.db.models.query_utils import Q, QNot, EmptyResultSet
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from django.db.models import signals, loading, sql
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from django.dispatch import dispatcher
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from django.utils.datastructures import SortedDict
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from django.utils.encoding import smart_unicode
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from django.contrib.contenttypes import generic
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try:
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set
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except NameError:
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from sets import Set as set # Python 2.3 fallback
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# Used to control how many objects are worked with at once in some cases (e.g.
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# when deleting objects).
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CHUNK_SIZE = 100
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class _QuerySet(object):
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"Represents a lazy database lookup for a set of objects"
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def __init__(self, model=None, query=None):
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self.model = model
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self.query = query or sql.Query(self.model, connection)
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self._result_cache = None
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########################
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# PYTHON MAGIC METHODS #
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########################
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def __repr__(self):
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return repr(self._get_data())
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def __len__(self):
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return len(self._get_data())
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def __iter__(self):
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return iter(self._get_data())
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def __getitem__(self, k):
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"Retrieve an item or slice from the set of results."
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if not isinstance(k, (slice, int, long)):
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raise TypeError
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assert ((not isinstance(k, slice) and (k >= 0))
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or (isinstance(k, slice) and (k.start is None or k.start >= 0)
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and (k.stop is None or k.stop >= 0))), \
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"Negative indexing is not supported."
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if self._result_cache is not None:
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return self._result_cache[k]
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if isinstance(k, slice):
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qs = self._clone()
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qs.query.set_limits(k.start, k.stop)
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return k.step and list(qs)[::k.step] or qs
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try:
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qs = self._clone()
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qs.query.set_limits(k, k + 1)
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return list(qs)[0]
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except self.model.DoesNotExist, e:
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raise IndexError, e.args
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def __and__(self, other):
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combined = self._clone()
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combined.query.combine(other.query, sql.AND)
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return combined
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def __or__(self, other):
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combined = self._clone()
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combined.query.combine(other.query, sql.OR)
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return combined
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####################################
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# METHODS THAT DO DATABASE QUERIES #
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####################################
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def iterator(self):
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"""
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An iterator over the results from applying this QuerySet to the
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database.
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"""
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fill_cache = self.query.select_related
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max_depth = self.query.max_depth
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index_end = len(self.model._meta.fields)
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extra_select = self.query.extra_select.keys()
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for row in self.query.results_iter():
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if fill_cache:
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obj, index_end = get_cached_row(klass=self.model, row=row,
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index_start=0, max_depth=max_depth)
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else:
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obj = self.model(*row[:index_end])
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for i, k in enumerate(extra_select):
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setattr(obj, k, row[index_end + i])
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yield obj
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def count(self):
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"""
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Performs a SELECT COUNT() and returns the number of records as an
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integer.
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If the queryset is already cached (i.e. self._result_cache is set) this
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simply returns the length of the cached results set to avoid multiple
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SELECT COUNT(*) calls.
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"""
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if self._result_cache is not None:
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return len(self._result_cache)
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return self.query.get_count()
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def get(self, *args, **kwargs):
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"""
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Performs the query and returns a single object matching the given
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keyword arguments.
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"""
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clone = self.filter(*args, **kwargs)
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obj_list = list(clone)
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if len(obj_list) < 1:
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raise self.model.DoesNotExist("%s matching query does not exist."
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% self.model._meta.object_name)
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elif len(obj_list) > 1:
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raise self.model.MultipleObjectsReturned("get() returned more than one %s -- it returned %s! Lookup parameters were %s"
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% (self.model._meta.object_name, len(obj_list), kwargs))
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return obj_list[0]
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def create(self, **kwargs):
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"""
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Create a new object with the given kwargs, saving it to the database
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and returning the created object.
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"""
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obj = self.model(**kwargs)
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obj.save()
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return obj
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def get_or_create(self, **kwargs):
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"""
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Looks up an object with the given kwargs, creating one if necessary.
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Returns a tuple of (object, created), where created is a boolean
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specifying whether an object was created.
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"""
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assert kwargs, \
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'get_or_create() must be passed at least one keyword argument'
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defaults = kwargs.pop('defaults', {})
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try:
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return self.get(**kwargs), False
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except self.model.DoesNotExist:
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params = dict([(k, v) for k, v in kwargs.items() if '__' not in k])
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params.update(defaults)
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obj = self.model(**params)
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obj.save()
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return obj, True
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def latest(self, field_name=None):
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"""
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Returns the latest object, according to the model's 'get_latest_by'
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option or optional given field_name.
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"""
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latest_by = field_name or self.model._meta.get_latest_by
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assert bool(latest_by), "latest() requires either a field_name parameter or 'get_latest_by' in the model"
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assert self.query.can_filter(), \
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"Cannot change a query once a slice has been taken."
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obj = self._clone()
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obj.query.set_limits(high=1)
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obj.query.add_ordering('-%s' % latest_by)
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return obj.get()
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def in_bulk(self, id_list):
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"""
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Returns a dictionary mapping each of the given IDs to the object with
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that ID.
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"""
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assert self.query.can_filter(), \
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"Cannot use 'limit' or 'offset' with in_bulk"
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assert isinstance(id_list, (tuple, list)), \
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"in_bulk() must be provided with a list of IDs."
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if not id_list:
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return {}
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qs = self._clone()
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qs.query.add_filter(('pk__in', id_list))
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return dict([(obj._get_pk_val(), obj) for obj in qs.iterator()])
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# XXX Mostly DONE
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def delete(self):
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"""
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Deletes the records in the current QuerySet.
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"""
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assert self.query.can_filter(), \
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"Cannot use 'limit' or 'offset' with delete."
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del_query = self._clone()
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# Disable non-supported fields.
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del_query.query.select_related = False
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del_query.query.clear_ordering()
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# Delete objects in chunks to prevent the list of related objects from
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# becoming too long.
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more_objects = True
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while more_objects:
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# Collect all the objects to be deleted in this chunk, and all the
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# objects that are related to the objects that are to be deleted.
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seen_objs = SortedDict()
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more_objects = False
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for object in del_query[:CHUNK_SIZE]:
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more_objects = True
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object._collect_sub_objects(seen_objs)
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# If one or more objects were found, delete them.
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# Otherwise, stop looping.
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# FIXME: Does "if seen_objs:.." work here? If so, we can get rid of
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# more_objects.
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if more_objects:
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delete_objects(seen_objs)
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# Clear the result cache, in case this QuerySet gets reused.
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self._result_cache = None
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delete.alters_data = True
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##################################################
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# PUBLIC METHODS THAT RETURN A QUERYSET SUBCLASS #
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##################################################
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def values(self, *fields):
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return self._clone(klass=ValuesQuerySet, setup=True, _fields=fields)
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def dates(self, field_name, kind, order='ASC'):
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"""
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Returns a list of datetime objects representing all available dates
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for the given field_name, scoped to 'kind'.
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"""
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assert kind in ("month", "year", "day"), \
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"'kind' must be one of 'year', 'month' or 'day'."
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assert order in ('ASC', 'DESC'), \
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"'order' must be either 'ASC' or 'DESC'."
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# Let the FieldDoesNotExist exception propagate.
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field = self.model._meta.get_field(field_name, many_to_many=False)
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assert isinstance(field, DateField), "%r isn't a DateField." \
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% field_name
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return self._clone(klass=DateQuerySet, setup=True, _field=field,
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_kind=kind, _order=order)
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##################################################################
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# PUBLIC METHODS THAT ALTER ATTRIBUTES AND RETURN A NEW QUERYSET #
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##################################################################
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def all(self):
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"""
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Returns a new QuerySet that is a copy of the current one. This allows a
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QuerySet to proxy for a model manager in some cases.
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"""
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return self._clone()
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def filter(self, *args, **kwargs):
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"""
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Returns a new QuerySet instance with the args ANDed to the existing
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set.
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"""
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return self._filter_or_exclude(None, *args, **kwargs)
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def exclude(self, *args, **kwargs):
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"""
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Returns a new QuerySet instance with NOT (args) ANDed to the existing
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set.
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"""
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return self._filter_or_exclude(QNot, *args, **kwargs)
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def _filter_or_exclude(self, mapper, *args, **kwargs):
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# mapper is a callable used to transform Q objects,
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# or None for identity transform.
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if mapper is None:
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mapper = lambda x: x
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if args or kwargs:
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assert self.query.can_filter(), \
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"Cannot filter a query once a slice has been taken."
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clone = self._clone()
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if kwargs:
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clone.query.add_q(mapper(Q(**kwargs)))
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for arg in args:
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clone.query.add_q(mapper(arg))
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return clone
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def complex_filter(self, filter_obj):
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"""
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Returns a new QuerySet instance with filter_obj added to the filters.
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filter_obj can be a Q object (or anything with an add_to_query()
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method) or a dictionary of keyword lookup arguments.
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This exists to support framework features such as 'limit_choices_to',
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and usually it will be more natural to use other methods.
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"""
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if isinstance(filter_obj, Q) or hasattr(filter_obj, 'add_to_query'):
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return self._filter_or_exclude(None, filter_obj)
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else:
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return self._filter_or_exclude(None, **filter_obj)
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def select_related(self, true_or_false=True, depth=0):
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"""Returns a new QuerySet instance that will select related objects."""
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obj = self._clone()
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obj.query.select_related = true_or_false
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if depth:
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obj.query.max_depth = depth
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return obj
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def order_by(self, *field_names):
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"""Returns a new QuerySet instance with the ordering changed."""
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assert self.query.can_filter(), \
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"Cannot reorder a query once a slice has been taken."
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obj = self._clone()
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obj.query.clear_ordering()
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obj.query.add_ordering(*field_names)
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return obj
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def distinct(self, true_or_false=True):
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"""
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Returns a new QuerySet instance that will select only distinct results.
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"""
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obj = self._clone()
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obj.query.distinct = true_or_false
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return obj
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def extra(self, select=None, where=None, params=None, tables=None,
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order_by=None):
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"""
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Add extra SQL fragments to the query.
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"""
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assert self.query.can_filter(), \
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"Cannot change a query once a slice has been taken"
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clone = self._clone()
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if select:
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clone.query.extra_select.update(select)
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if where:
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clone.query.extra_where.extend(where)
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if params:
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clone.query.extra_params.extend(params)
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if tables:
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clone.query.extra_tables.extend(tables)
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if order_by:
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clone.query.extra_order_by = order_by
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return clone
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###################
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# PRIVATE METHODS #
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###################
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def _clone(self, klass=None, setup=False, **kwargs):
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if klass is None:
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klass = self.__class__
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c = klass(model=self.model, query=self.query.clone())
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c.__dict__.update(kwargs)
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if setup and hasattr(c, '_setup_query'):
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c._setup_query()
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return c
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def _get_data(self):
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if self._result_cache is None:
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self._result_cache = list(self.iterator())
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return self._result_cache
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# Use the backend's QuerySet class if it defines one. Otherwise, use _QuerySet.
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if connection.features.uses_custom_queryset:
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QuerySet = connection.ops.query_set_class(_QuerySet)
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else:
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QuerySet = _QuerySet
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class ValuesQuerySet(QuerySet):
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def __init__(self, *args, **kwargs):
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super(ValuesQuerySet, self).__init__(*args, **kwargs)
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# select_related isn't supported in values().
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self.query.select_related = False
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# QuerySet.clone() will also set up the _fields attribute with the
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# names of the model fields to select.
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def iterator(self):
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self.field_names.extend([f for f in self.query.extra_select.keys()])
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for row in self.query.results_iter():
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yield dict(zip(self.field_names, row))
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def _setup_query(self):
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"""
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Sets up any special features of the query attribute.
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Called by the _clone() method after initialising the rest of the
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instance.
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"""
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# Construct two objects:
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# - fields is a list of Field objects to fetch.
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# - field_names is a list of field names, which will be the keys in
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# the resulting dictionaries.
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# 'fields' is used to configure the query, whilst field_names is stored
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# in this object for use by iterator().
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if self._fields:
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opts = self.model._meta
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all = dict([(field.column, field) for field in opts.fields])
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for field in opts.fields:
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all[field.name] = field
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if not self.query.extra_select:
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try:
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fields = [all[f] for f in self._fields]
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except KeyError, e:
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raise FieldDoesNotExist('%s has no field named %r'
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% (opts.object_name, e.args[0]))
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field_names = list(self._fields)
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else:
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fields = []
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field_names = []
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for f in self._fields:
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if f in all:
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fields.append(all[f])
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field_names.append(f)
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elif not self.query.extra_select.has_key(f):
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raise FieldDoesNotExist('%s has no field named %r'
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% (self.model._meta.object_name, f))
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else: # Default to all fields.
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fields = self.model._meta.fields
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field_names = [f.attname for f in fields]
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self.query.add_local_columns([f.column for f in fields])
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self.query.default_cols = False
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self.field_names = field_names
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def _clone(self, klass=None, setup=False, **kwargs):
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"""
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Cloning a ValuesQuerySet preserves the current fields.
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"""
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c = super(ValuesQuerySet, self)._clone(klass, **kwargs)
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c._fields = self._fields[:]
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c.field_names = self.field_names[:]
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if setup and hasattr(c, '_setup_query'):
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c._setup_query()
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return c
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class DateQuerySet(QuerySet):
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def iterator(self):
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return self.query.results_iter()
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def _setup_query(self):
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"""
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Sets up any special features of the query attribute.
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Called by the _clone() method after initialising the rest of the
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instance.
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"""
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self.query = self.query.clone(klass=sql.DateQuery, setup=True)
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self.query.select = []
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self.query.add_date_select(self._field.column, self._kind, self._order)
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if self._field.null:
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self.query.add_filter(('%s__isnull' % self._field.name, True))
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def _clone(self, klass=None, setup=False, **kwargs):
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c = super(DateQuerySet, self)._clone(klass, False, **kwargs)
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c._field = self._field
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c._kind = self._kind
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if setup and hasattr(c, '_setup_query'):
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c._setup_query()
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return c
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class EmptyQuerySet(QuerySet):
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def __init__(self, model=None, query=None):
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super(EmptyQuerySet, self).__init__(model, query)
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self._result_cache = []
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def count(self):
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return 0
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def delete(self):
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pass
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def _clone(self, klass=None, setup=False, **kwargs):
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c = super(EmptyQuerySet, self)._clone(klass, **kwargs)
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c._result_cache = []
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return c
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def iterator(self):
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# This slightly odd construction is because we need an empty generator
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# (it raises StopIteration immediately).
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yield iter([]).next()
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# QOperator, QAnd and QOr are temporarily retained for backwards compatibility.
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# All the old functionality is now part of the 'Q' class.
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class QOperator(Q):
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def __init__(self, *args, **kwargs):
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warnings.warn('Use Q instead of QOr, QAnd or QOperation.',
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DeprecationWarning, stacklevel=2)
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QOr = QAnd = QOperator
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def get_cached_row(klass, row, index_start, max_depth=0, cur_depth=0):
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"""Helper function that recursively returns an object with cache filled"""
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# If we've got a max_depth set and we've exceeded that depth, bail now.
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if max_depth and cur_depth > max_depth:
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return None
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index_end = index_start + len(klass._meta.fields)
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obj = klass(*row[index_start:index_end])
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for f in klass._meta.fields:
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if f.rel and not f.null:
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cached_row = get_cached_row(f.rel.to, row, index_end, max_depth, cur_depth+1)
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if cached_row:
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rel_obj, index_end = cached_row
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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.
|
|
"""
|
|
ordered_classes = seen_objs.keys()
|
|
ordered_classes.reverse()
|
|
|
|
for cls in ordered_classes:
|
|
seen_objs[cls] = seen_objs[cls].items()
|
|
seen_objs[cls].sort()
|
|
|
|
# Pre notify all instances to be deleted
|
|
for pk_val, instance in seen_objs[cls]:
|
|
dispatcher.send(signal=signals.pre_delete, sender=cls,
|
|
instance=instance)
|
|
|
|
pk_list = [pk for pk,instance in seen_objs[cls]]
|
|
del_query = sql.DeleteQuery(cls, connection)
|
|
del_query.delete_batch_related(pk_list)
|
|
|
|
update_query = sql.UpdateQuery(cls, connection)
|
|
for field in cls._meta.fields:
|
|
if field.rel and field.null and field.rel.to in seen_objs:
|
|
update_query.clear_related(field, pk_list)
|
|
|
|
# Now delete the actual data
|
|
for cls in ordered_classes:
|
|
seen_objs[cls].reverse()
|
|
pk_list = [pk for pk,instance in seen_objs[cls]]
|
|
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 seen_objs[cls]:
|
|
for field in cls._meta.fields:
|
|
if field.rel and field.null and field.rel.to in seen_objs:
|
|
setattr(instance, field.attname, None)
|
|
|
|
dispatcher.send(signal=signals.post_delete, sender=cls,
|
|
instance=instance)
|
|
setattr(instance, cls._meta.pk.attname, None)
|
|
|
|
transaction.commit_unless_managed()
|
|
|