Merge pull request #297 from namespaceMarcello/check-paging-without-counting

Check for a second page of messages without counting the room

app/models/message/pagination.rb

@@ -49,7 +49,7 @@ module Message::Pagination
     end
 
     def paged?
-      count > PAGE_SIZE
+      offset(PAGE_SIZE).exists?
     end
   end
 end

test/models/message_test.rb

@@ -65,6 +65,18 @@ class MessageTest < ActiveSupport::TestCase
     assert_equal room.messages.ordered.first(Message::Pagination::PAGE_SIZE).map(&:id), room.messages.first_page.map(&:id)
   end
 
+  test "paged? tells whether a room has more than a page of messages without counting them all" do
+    room = Rooms::Closed.create!(name: "Paging", creator: users(:david))
+    Message.insert_all Array.new(Message::Pagination::PAGE_SIZE) { |i| { room_id: room.id, creator_id: users(:david).id, client_message_id: "paging-#{i}" } }
+
+    assert_no_queries_match(/COUNT/i) do
+      assert_not room.messages.paged?
+
+      Message.insert_all [ { room_id: room.id, creator_id: users(:david).id, client_message_id: "paging-next" } ]
+      assert room.messages.paged?
+    end
+  end
+
   test "search reads quotes and operator words in the query as text" do
     message = rooms(:designers).messages.create!(body: "Say hi, NOT bye", client_message_id: "quoted", creator: users(:david))