Fixed #18375 -- Removed dict-ordering dependency for F-expressions

F() expressions reuse joins like any lookup in a .filter() call -
reuse multijoins generated in the same .filter() call else generate
new joins. Also, lookups can now reuse joins generated by F().

This change is backwards incompatible, but it is required to prevent
dict randomization from generating different queries depending on
.filter() kwarg ordering. The new way is also more consistent in how
joins are reused.
This commit is contained in:
Anssi Kääriäinen 2012-11-22 20:27:28 +02:00
parent 7b9a1fb964
commit 90b86291d0
4 changed files with 52 additions and 4 deletions

View File

@ -1,14 +1,16 @@
from django.core.exceptions import FieldError
from django.db.models.constants import LOOKUP_SEP
from django.db.models.fields import FieldDoesNotExist
from django.db.models.sql.constants import REUSE_ALL
class SQLEvaluator(object):
def __init__(self, expression, query, allow_joins=True):
def __init__(self, expression, query, allow_joins=True, reuse=REUSE_ALL):
self.expression = expression
self.opts = query.get_meta()
self.cols = []
self.contains_aggregate = False
self.reuse = reuse
self.expression.prepare(self, query, allow_joins)
def prepare(self):
@ -50,9 +52,10 @@ class SQLEvaluator(object):
try:
field, source, opts, join_list, last, _ = query.setup_joins(
field_list, query.get_meta(),
query.get_initial_alias(), False)
query.get_initial_alias(), self.reuse)
col, _, join_list = query.trim_joins(source, join_list, last, False)
if self.reuse is not None and self.reuse != REUSE_ALL:
self.reuse.update(join_list)
self.cols.append((node, (join_list[-1], col)))
except FieldDoesNotExist:
raise FieldError("Cannot resolve keyword %r into field. "

View File

@ -1096,7 +1096,7 @@ class Query(object):
value = value()
elif isinstance(value, ExpressionNode):
# If value is a query expression, evaluate it
value = SQLEvaluator(value, self)
value = SQLEvaluator(value, self, reuse=can_reuse)
having_clause = value.contains_aggregate
for alias, aggregate in self.aggregates.items():

View File

@ -589,6 +589,12 @@ Miscellaneous
:ref:`Q() expressions <complex-lookups-with-q>` and ``QuerySet`` combining where
the operators are used as boolean AND and OR operators.
* In a ``filter()`` call, when :ref:`F() expressions <query-expressions>`
contained lookups spanning multi-valued relations, they didn't always reuse
the same relations as other lookups along the same chain. This was changed,
and now F() expressions will always use the same relations as other lookups
within the same ``filter()`` call.
* The :ttag:`csrf_token` template tag is no longer enclosed in a div. If you need
HTML validation against pre-HTML5 Strict DTDs, you should add a div around it
in your pages.

View File

@ -219,3 +219,42 @@ class ExpressionsTests(TestCase):
)
acme.num_employees = F("num_employees") + 16
self.assertRaises(TypeError, acme.save)
def test_ticket_18375_join_reuse(self):
# Test that reverse multijoin F() references and the lookup target
# the same join. Pre #18375 the F() join was generated first, and the
# lookup couldn't reuse that join.
qs = Employee.objects.filter(
company_ceo_set__num_chairs=F('company_ceo_set__num_employees'))
self.assertEqual(str(qs.query).count('JOIN'), 1)
def test_ticket_18375_kwarg_ordering(self):
# The next query was dict-randomization dependent - if the "gte=1"
# was seen first, then the F() will reuse the join generated by the
# gte lookup, if F() was seen first, then it generated a join the
# other lookups could not reuse.
qs = Employee.objects.filter(
company_ceo_set__num_chairs=F('company_ceo_set__num_employees'),
company_ceo_set__num_chairs__gte=1)
self.assertEqual(str(qs.query).count('JOIN'), 1)
def test_ticket_18375_kwarg_ordering_2(self):
# Another similar case for F() than above. Now we have the same join
# in two filter kwargs, one in the lhs lookup, one in F. Here pre
# #18375 the amount of joins generated was random if dict
# randomization was enabled, that is the generated query dependend
# on which clause was seen first.
qs = Employee.objects.filter(
company_ceo_set__num_employees=F('pk'),
pk=F('company_ceo_set__num_employees')
)
self.assertEqual(str(qs.query).count('JOIN'), 1)
def test_ticket_18375_chained_filters(self):
# Test that F() expressions do not reuse joins from previous filter.
qs = Employee.objects.filter(
company_ceo_set__num_employees=F('pk')
).filter(
company_ceo_set__num_employees=F('company_ceo_set__num_employees')
)
self.assertEqual(str(qs.query).count('JOIN'), 2)