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[1.5.x] Fixed #20091 -- Oracle null promotion for empty strings

Backpatch of e17fa9e
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commit 207117ae731096d8148c17c6ca16f06ebf18537c 1 parent 5e2bb12
@akaariai akaariai authored
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9 django/db/models/sql/query.py
@@ -1106,7 +1106,14 @@ def add_filter(self, filter_expr, connector=AND, negate=False, trim=False,
# If value is a query expression, evaluate it
value = SQLEvaluator(value, self, reuse=can_reuse)
having_clause = value.contains_aggregate
-
+ # For Oracle '' is equivalent to null. The check needs to be done
+ # at this stage because join promotion can't be done at compiler
+ # stage. Using DEFAULT_DB_ALIAS isn't nice, but it is the best we
+ # can do here. Similar thing is done in is_nullable(), too.
+ if (connections[DEFAULT_DB_ALIAS].features.interprets_empty_strings_as_nulls and
+ lookup_type == 'exact' and value == ''):
+ value = True
+ lookup_type = 'isnull'
for alias, aggregate in self.aggregates.items():
if alias in (parts[0], LOOKUP_SEP.join(parts)):
entry = self.where_class()
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9 tests/regressiontests/queries/tests.py
@@ -1533,7 +1533,6 @@ def test_tickets_8921_9188(self):
# Nested queries are possible (although should be used with care, since
# they have performance problems on backends like MySQL.
-
self.assertQuerysetEqual(
Annotation.objects.filter(notes__in=Note.objects.filter(note="n1")),
['<Annotation: a1>']
@@ -2142,3 +2141,11 @@ def test_ticket_17886(self):
# so we can use INNER JOIN for it. However, we can NOT use INNER JOIN
# for the b->c join, as a->b is nullable.
self.assertEqual(str(qset.query).count('INNER JOIN'), 1)
+
+class EmptyStringPromotionTests(TestCase):
+ def test_empty_string_promotion(self):
+ qs = RelatedObject.objects.filter(single__name='')
+ if connection.features.interprets_empty_strings_as_nulls:
+ self.assertIn('LEFT OUTER JOIN', str(qs.query))
+ else:
+ self.assertNotIn('LEFT OUTER JOIN', str(qs.query))
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