From 1cdfbde4db1ac6bbddb2cf8dd5192831bc0f9ce3 Mon Sep 17 00:00:00 2001
From: Josh Smeaton <josh.smeaton@gmail.com>
Date: Mon, 29 Dec 2014 09:15:00 +1100
Subject: [PATCH] Fixed #23753 -- Oracle failure with Coalesce

---
 django/db/models/functions.py | 12 ++++++++++++
 tests/db_functions/tests.py   | 12 ++++++++++++
 2 files changed, 24 insertions(+)

diff --git a/django/db/models/functions.py b/django/db/models/functions.py
index f2252000cd..f16cf10b15 100644
--- a/django/db/models/functions.py
+++ b/django/db/models/functions.py
@@ -16,6 +16,18 @@ class Coalesce(Func):
             raise ValueError('Coalesce must take at least two expressions')
         super(Coalesce, self).__init__(*expressions, **extra)
 
+    def as_oracle(self, compiler, connection):
+        # we can't mix TextField (NCLOB) and CharField (NVARCHAR), so convert
+        # all fields to NCLOB when we expect NCLOB
+        if self.output_field.get_internal_type() == 'TextField':
+            class ToNCLOB(Func):
+                function = 'TO_NCLOB'
+
+            expressions = [
+                ToNCLOB(expression) for expression in self.get_source_expressions()]
+            self.set_source_expressions(expressions)
+        return super(Coalesce, self).as_sql(compiler, connection)
+
 
 class ConcatPair(Func):
     """
diff --git a/tests/db_functions/tests.py b/tests/db_functions/tests.py
index 089fd11a8a..2ab18b61e0 100644
--- a/tests/db_functions/tests.py
+++ b/tests/db_functions/tests.py
@@ -56,6 +56,18 @@ class FunctionTests(TestCase):
             lambda a: a.headline
         )
 
+        # mixed Text and Char wrapped
+        article = Article.objects.annotate(
+            headline=Coalesce(Lower('summary'), Lower('text'), output_field=TextField()),
+        )
+
+        self.assertQuerysetEqual(
+            article.order_by('title'), [
+                lorem_ipsum.lower(),
+            ],
+            lambda a: a.headline
+        )
+
     def test_concat(self):
         Author.objects.create(name='Jayden')
         Author.objects.create(name='John Smith', alias='smithj', goes_by='John')