1 files changed, 52 insertions, 0 deletions
diff --git a/activerecord/test/cases/adapters/postgresql/optimizer_hints_test.rb b/activerecord/test/cases/adapters/postgresql/optimizer_hints_test.rb
new file mode 100644
index 0000000000..5b9f5e0832
--- /dev/null
+++ b/activerecord/test/cases/adapters/postgresql/optimizer_hints_test.rb
@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+require "cases/helper"
+require "models/post"
+
+if supports_optimizer_hints?
+  class PostgresqlOptimzerHintsTest < ActiveRecord::PostgreSQLTestCase
+    fixtures :posts
+
+    def setup
+      enable_extension!("pg_hint_plan", ActiveRecord::Base.connection)
+    end
+
+    def test_optimizer_hints
+      assert_sql(%r{\ASELECT /\*\+ SeqScan\(posts\) \*/}) do
+        posts = Post.optimizer_hints("SeqScan(posts)")
+        posts = posts.select(:id).where(author_id: [0, 1])
+        assert_includes posts.explain, "Seq Scan on posts"
+      end
+    end
+
+    def test_optimizer_hints_with_count_subquery
+      assert_sql(%r{\ASELECT /\*\+ SeqScan\(posts\) \*/}) do
+        posts = Post.optimizer_hints("SeqScan(posts)")
+        posts = posts.select(:id).where(author_id: [0, 1]).limit(5)
+        assert_equal 5, posts.count
+      end
+    end
+
+    def test_optimizer_hints_is_sanitized
+      assert_sql(%r{\ASELECT /\*\+ SeqScan\(posts\) \*/}) do
+        posts = Post.optimizer_hints("/*+ SeqScan(posts) */")
+        posts = posts.select(:id).where(author_id: [0, 1])
+        assert_includes posts.explain, "Seq Scan on posts"
+      end
+
+      assert_sql(%r{\ASELECT /\*\+  "posts"\.\*,  \*/}) do
+        posts = Post.optimizer_hints("**// \"posts\".*, //**")
+        posts = posts.select(:id).where(author_id: [0, 1])
+        assert_equal({ "id" => 1 }, posts.first.as_json)
+      end
+    end
+
+    def test_optimizer_hints_with_unscope
+      assert_sql(%r{\ASELECT "posts"\."id"}) do
+        posts = Post.optimizer_hints("/*+ SeqScan(posts) */")
+        posts = posts.select(:id).where(author_id: [0, 1])
+        posts.unscope(:optimizer_hints).load
+      end
+    end
+  end
+end