Fixed #11402: added a `QuerySet.exists()` method. Thanks, Alex Gaynor. (b79702b2) · Commits · Dom Sekotill / django

django/db/models/base.py

+1 −8

Original line number	Diff line number	Diff line
		@@ -3,11 +3,6 @@ import types
		import sys
		import os
		from itertools import izip
		try:
		set
		except NameError:
		from sets import Set as set # Python 2.3 fallback.

		import django.db.models.manager # Imported to register signal handler.
		from django.core.exceptions import ObjectDoesNotExist, MultipleObjectsReturned, FieldError
		from django.db.models.fields import AutoField, FieldDoesNotExist
		@@ -22,7 +17,6 @@ from django.utils.functional import curry
		from django.utils.encoding import smart_str, force_unicode, smart_unicode
		from django.conf import settings


		class ModelBase(type):
		"""
		Metaclass for all models.
		@@ -236,7 +230,6 @@ class ModelBase(type):

		signals.class_prepared.send(sender=cls)


		class Model(object):
		__metaclass__ = ModelBase
		_deferred = False
		@@ -467,7 +460,7 @@ class Model(object):
		if pk_set:
		# Determine whether a record with the primary key already exists.
		if (force_update or (not force_insert and
		manager.filter(pk=pk_val).extra(select={'a': 1}).values('a').order_by())):
		manager.filter(pk=pk_val).exists())):
		# It does already exist, so do an UPDATE.
		if force_update or non_pks:
		values = [(f, None, (raw and getattr(self, f.attname) or f.pre_save(self, False))) for f in non_pks]

+3 −1

Original line number	Diff line number	Diff line
		import copy

		from django.db.models.query import QuerySet, EmptyQuerySet, insert_query
		from django.db.models import signals
		from django.db.models.fields import FieldDoesNotExist
		@@ -173,6 +172,9 @@ class Manager(object):
		def only(self, args, *kwargs):
		return self.get_query_set().only(args, *kwargs)

		def exists(self, args, *kwargs):
		return self.get_query_ste().exists(args, *kwargs)

		def _insert(self, values, **kwargs):
		return insert_query(self.model, values, **kwargs)

+5 −7

Original line number	Diff line number	Diff line
		@@ -2,20 +2,13 @@
		The main QuerySet implementation. This provides the public API for the ORM.
		"""

		try:
		set
		except NameError:
		from sets import Set as set # Python 2.3 fallback

		from copy import deepcopy

		from django.db import connection, transaction, IntegrityError
		from django.db.models.aggregates import Aggregate
		from django.db.models.fields import DateField
		from django.db.models.query_utils import Q, select_related_descend, CollectedObjects, CyclicDependency, deferred_class_factory
		from django.db.models import signals, sql


		# Used to control how many objects are worked with at once in some cases (e.g.
		# when deleting objects).
		CHUNK_SIZE = 100
		@@ -444,6 +437,11 @@ class QuerySet(object):
		return query.execute_sql(None)
		_update.alters_data = True

		def exists(self):
		if self._result_cache is None:
		return self.query.has_results()
		return bool(self._result_cache)

		##################################################
		# PUBLIC METHODS THAT RETURN A QUERYSET SUBCLASS #
		##################################################

+9 −6

Original line number	Diff line number	Diff line
		@@ -8,7 +8,6 @@ all about the internals of models in order to get the information it needs.
		"""

		from copy import deepcopy

		from django.utils.tree import Node
		from django.utils.datastructures import SortedDict
		from django.utils.encoding import force_unicode
		@@ -24,11 +23,6 @@ from django.core.exceptions import FieldError
		from datastructures import EmptyResultSet, Empty, MultiJoin
		from constants import *

		try:
		set
		except NameError:
		from sets import Set as set # Python 2.3 fallback

		__all__ = ['Query', 'BaseQuery']

		class BaseQuery(object):
		@@ -384,6 +378,15 @@ class BaseQuery(object):

		return number

		def has_results(self):
		q = self.clone()
		q.add_extra({'a': 1}, None, None, None, None, None)
		q.add_fields(())
		q.set_extra_mask(('a',))
		q.set_aggregate_mask(())
		q.clear_ordering()
		return bool(q.execute_sql())

		def as_sql(self, with_limits=True, with_col_aliases=False):
		"""
		Creates the SQL for this query. Returns the SQL string and list of

+2 −6

Original line number	Diff line number	Diff line
		@@ -319,9 +319,7 @@ class BaseModelForm(BaseForm):
		if self.instance.pk is not None:
		qs = qs.exclude(pk=self.instance.pk)

		# This cute trick with extra/values is the most efficient way to
		# tell if a particular query returns any results.
		if qs.extra(select={'a': 1}).values('a').order_by():
		if qs.exists():
		if len(unique_check) == 1:
		self._errors[unique_check[0]] = ErrorList([self.unique_error_message(unique_check)])
		else:
		@@ -354,9 +352,7 @@ class BaseModelForm(BaseForm):
		if self.instance.pk is not None:
		qs = qs.exclude(pk=self.instance.pk)

		# This cute trick with extra/values is the most efficient way to
		# tell if a particular query returns any results.
		if qs.extra(select={'a': 1}).values('a').order_by():
		if qs.exists():
		self._errors[field] = ErrorList([
		self.date_error_message(lookup_type, field, unique_for)
		])