[3.0.x] Fixed #31584 -- Fixed crash when chaining values()/values_list() after Exists() annotation and aggregation on Oracle.

Oracle requires the EXISTS expression to be wrapped in a CASE WHEN in
the GROUP BY clause.

Regression in efa1908f662c19038a944129c81462485c4a9fe8.
Backport of 3a941230c85b2702a5e1cd97e17251ce21057efa from master

5 files changed, 9 insertions, 5 deletions

diff --git a/django/db/backends/base/features.py b/django/db/backends/base/features.py
index 89b417c7de..20996f9cf5 100644
--- a/django/db/backends/base/features.py
+++ b/django/db/backends/base/features.py
@@ -289,7 +289,8 @@ class BaseDatabaseFeatures:
     # field(s)?
     allows_multiple_constraints_on_same_fields = True
 
-    # Does the backend support boolean expressions in the SELECT clause?
+    # Does the backend support boolean expressions in SELECT and GROUP BY
+    # clauses?
     supports_boolean_expr_in_select_clause = True
 
     def __init__(self, connection):
diff --git a/django/db/models/expressions.py b/django/db/models/expressions.py
index 2733fbada9..fee59551a8 100644
--- a/django/db/models/expressions.py
+++ b/django/db/models/expressions.py
@@ -1108,7 +1108,8 @@ class Exists(Subquery):
 
     def select_format(self, compiler, sql, params):
         # Wrap EXISTS() with a CASE WHEN expression if a database backend
-        # (e.g. Oracle) doesn't support boolean expression in the SELECT list.
+        # (e.g. Oracle) doesn't support boolean expression in SELECT or GROUP
+        # BY list.
         if not compiler.connection.features.supports_boolean_expr_in_select_clause:
             sql = 'CASE WHEN {} THEN 1 ELSE 0 END'.format(sql)
         return sql, params
diff --git a/django/db/models/sql/compiler.py b/django/db/models/sql/compiler.py
index 18365f1d75..ccec6fdc38 100644
--- a/django/db/models/sql/compiler.py
+++ b/django/db/models/sql/compiler.py
@@ -135,6 +135,7 @@ class SQLCompiler:
 
         for expr in expressions:
             sql, params = self.compile(expr)
+            sql, params = expr.select_format(self, sql, params)
             params_hash = make_hashable(params)
             if (sql, params_hash) not in seen:
                 result.append((sql, params))
diff --git a/docs/releases/3.0.7.txt b/docs/releases/3.0.7.txt
index 0f1188724a..def27a49ec 100644
--- a/docs/releases/3.0.7.txt
+++ b/docs/releases/3.0.7.txt
@@ -18,3 +18,7 @@ Bugfixes
 
 * Fixed a regression in Django 3.0 where aggregates used wrong annotations when
   a queryset has multiple subqueries annotations (:ticket:`31568`).
+
+* Fixed a regression in Django 3.0 where ``QuerySet.values()`` and
+  ``values_list()`` crashed if a queryset contained an aggregation and an
+  ``Exists()`` annotation on Oracle (:ticket:`31584`).
diff --git a/tests/annotations/tests.py b/tests/annotations/tests.py
index 0cdc9178b0..0064b14ed0 100644
--- a/tests/annotations/tests.py
+++ b/tests/annotations/tests.py
@@ -1,9 +1,7 @@
 import datetime
 from decimal import Decimal
-from unittest import skipIf
 
 from django.core.exceptions import FieldDoesNotExist, FieldError
-from django.db import connection
 from django.db.models import (
     BooleanField, CharField, Count, DateTimeField, Exists, ExpressionWrapper,
     F, Func, IntegerField, Max, NullBooleanField, OuterRef, Q, Subquery, Sum,
@@ -623,7 +621,6 @@ class NonAggregateAnnotationTestCase(TestCase):
         ).values('name')
         self.assertCountEqual(publisher_books_qs, [{'name': 'Sams'}, {'name': 'Morgan Kaufmann'}])
 
-    @skipIf(connection.vendor == 'oracle', 'See https://code.djangoproject.com/ticket/31584')
     def test_annotation_exists_aggregate_values_chaining(self):
         qs = Book.objects.values('publisher').annotate(
             has_authors=Exists(Book.authors.through.objects.filter(book=OuterRef('pk'))),