From d5088f838d837fc9e3109c828f18511055f20bea Mon Sep 17 00:00:00 2001
From: Vytis Banaitis <vytis.banaitis@gmail.com>
Date: Sun, 12 Feb 2017 16:43:04 +0200
Subject: [PATCH] Fixed #27828 -- Fixed a crash when subtracting
 Integer/DurationField from DateField on Oracle/PostgreSQL.

---
 django/db/models/expressions.py | 2 +-
 docs/releases/1.10.6.txt        | 3 +++
 tests/expressions/tests.py      | 6 ++++++
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/django/db/models/expressions.py b/django/db/models/expressions.py
index af8891da220..07d2b904a8e 100644
--- a/django/db/models/expressions.py
+++ b/django/db/models/expressions.py
@@ -383,7 +383,7 @@ class CombinedExpression(Expression):
             return DurationExpression(self.lhs, self.connector, self.rhs).as_sql(compiler, connection)
         if (lhs_output and rhs_output and self.connector == self.SUB and
             lhs_output.get_internal_type() in {'DateField', 'DateTimeField', 'TimeField'} and
-                lhs_output.get_internal_type() == lhs_output.get_internal_type()):
+                lhs_output.get_internal_type() == rhs_output.get_internal_type()):
             return TemporalSubtraction(self.lhs, self.rhs).as_sql(compiler, connection)
         expressions = []
         expression_params = []
diff --git a/docs/releases/1.10.6.txt b/docs/releases/1.10.6.txt
index 483854c0e66..b549ae1b9a4 100644
--- a/docs/releases/1.10.6.txt
+++ b/docs/releases/1.10.6.txt
@@ -14,3 +14,6 @@ Bugfixes
 
 * Fixed ``RequestDataTooBig`` and ``TooManyFieldsSent`` exceptions crashing
   rather than generating a bad request response (:ticket:`27820`).
+
+* Fixed a crash on Oracle and PostgreSQL when subtracting ``DurationField``
+  or ``IntegerField`` from ``DateField`` (:ticket:`27828`).
diff --git a/tests/expressions/tests.py b/tests/expressions/tests.py
index 0a414942178..5b754c88f1e 100644
--- a/tests/expressions/tests.py
+++ b/tests/expressions/tests.py
@@ -1184,6 +1184,12 @@ class FTimeDeltaTests(TestCase):
         ).order_by('name')
         self.assertQuerysetEqual(over_estimate, ['e3', 'e4'], lambda e: e.name)
 
+    def test_date_minus_duration(self):
+        more_than_4_days = Experiment.objects.filter(
+            assigned__lt=F('completed') - Value(datetime.timedelta(days=4), output_field=models.DurationField())
+        )
+        self.assertQuerysetEqual(more_than_4_days, ['e3', 'e4'], lambda e: e.name)
+
     def test_negative_timedelta_update(self):
         # subtract 30 seconds, 30 minutes, 2 hours and 2 days
         experiments = Experiment.objects.filter(name='e0').annotate(