Fix loaded relation batching with limits and reverse order

Author: fatkodima

activerecord/lib/active_record/relation/batches.rb

@@ -341,7 +341,13 @@ def batch_on_loaded_relation(relation:, start:, finish:, order:, batch_limit:)
 
         if start || finish
           records = records.filter do |record|
-            (start.nil? || record.id >= start) && (finish.nil? || record.id <= finish)
+            id = record.id
+
+            if order == :asc
+              (start.nil? || id >= start) && (finish.nil? || id <= finish)
+            else
+              (start.nil? || id <= start) && (finish.nil? || id >= finish)
+            end
           end
         end
 

activerecord/test/cases/batches_test.rb

@@ -506,6 +506,23 @@ def test_in_batches_when_loaded_runs_no_queries_with_start_and_end_arguments
     assert_equal posts.size - 2, batch_count
   end
 
+  def test_in_batches_when_loaded_runs_no_queries_with_start_and_end_arguments_and_reverse_order
+    posts = Post.all.order(id: :asc)
+    posts.load
+    batch_count = 0
+
+    start_id = posts.map(&:id)[-2]
+    finish_id = posts.map(&:id)[1]
+    assert_queries_count(0) do
+      posts.in_batches(of: 1, start: start_id, finish: finish_id, order: :desc) do |relation|
+        batch_count += 1
+        assert_kind_of ActiveRecord::Relation, relation
+      end
+    end
+
+    assert_equal posts.size - 2, batch_count
+  end
+
   def test_in_batches_when_loaded_can_return_an_enum
     posts = Post.all
     posts.load