Fixed #36821 -- Treated empty strings as NULL for iexact lookups on Oracle.

Signed-off-by: JaeHyuck Sa <wogur981208@gmail.com>

django/db/models/sql/query.py

@@ -1444,7 +1444,7 @@ class Query(BaseExpression):
         # DEFAULT_DB_ALIAS isn't nice but it's the best that can be done here.
         # A similar thing is done in is_nullable(), too.
         if (
-            lookup_name == "exact"
+            lookup_name in ("exact", "iexact")
             and lookup.rhs == ""
             and connections[DEFAULT_DB_ALIAS].features.interprets_empty_strings_as_nulls
         ):

tests/null_queries/models.py

@@ -7,7 +7,7 @@ class Poll(models.Model):
 
 class Choice(models.Model):
     poll = models.ForeignKey(Poll, models.CASCADE)
-    choice = models.CharField(max_length=200)
+    choice = models.CharField(max_length=200, null=True)
 
 
 # A set of models with an inner one pointing to two outer ones.

tests/null_queries/tests.py

@@ -1,5 +1,5 @@
 from django.core.exceptions import FieldError
-from django.test import TestCase
+from django.test import TestCase, skipUnlessDBFeature
 
 from .models import Choice, Inner, OuterA, OuterB, Poll
 
@@ -44,6 +44,18 @@ class NullQueriesTests(TestCase):
         with self.assertRaisesMessage(ValueError, "Cannot use None as a query value"):
             Choice.objects.filter(id__gt=None)
 
+    @skipUnlessDBFeature("interprets_empty_strings_as_nulls")
+    def test_empty_string_is_null(self):
+        p = Poll.objects.create(question="?")
+        c1 = Choice.objects.create(poll=p, choice=None)
+        c2 = Choice.objects.create(poll=p, choice="")
+        cases = [{"choice__exact": ""}, {"choice__iexact": ""}]
+        for lookup in cases:
+            with self.subTest(lookup):
+                self.assertSequenceEqual(
+                    Choice.objects.filter(**lookup).order_by("id"), [c1, c2]
+                )
+
     def test_unsaved(self):
         poll = Poll(question="How?")
         msg = (