Moving chat messages to a new channel jumbled them all up

martin · May 23, 2022, 1:57am

Thanks for reporting this, I did try to take this into account with the feature but I think I got a little too lucky with the testing I did So we do indeed set all the timestamps to the same thing here:

github.com/discourse/discourse-chat

lib/message_mover.rb

82c0ee7f1


      
          def create_destination_messages_in_channel(destination_channel)
            moved_message_ids = DB.query_single(<<~SQL, message_ids: @ordered_source_message_ids, destination_channel_id: destination_channel.id)
              INSERT INTO chat_messages(chat_channel_id, user_id, message, cooked, cooked_version, created_at, updated_at)
              SELECT :destination_channel_id, user_id, message, cooked, cooked_version, CLOCK_TIMESTAMP(), CLOCK_TIMESTAMP()
              FROM chat_messages
              WHERE id IN (:message_ids)
              RETURNING id
            SQL

The problem is that we do not want to interleave the moved messages between the existing channel messages, and it gets harder and harder the more messages your move.

A question before I dive too deep on this – can you remember and identify which messages are out of place? Is there just a couple, or are they completely out of order? I think what has possibly caused the discrepancy is that when we are fetching messages for a channel, we do it by ID order (which we order DESC and then reverse in most cases):

github.com/discourse/discourse-chat

app/controllers/chat_controller.rb

82c0ee7f1


      
          messages = preloaded_chat_message_query.where(chat_channel: @chat_channel)
          
          order_direction = :desc
          if params[:before_message_id]
            messages = messages.where("id < ?", params[:before_message_id])
          end
          
          if params[:after_message_id]
            messages = messages.where("id > ?", params[:after_message_id])
            order_direction = :asc
          end

github.com/discourse/discourse-chat

app/controllers/chat_controller.rb

82c0ee7f1


      
          chat_view = ChatView.new(
            chat_channel: @chat_channel,
            chat_messages: params[:after_message_id] ? messages : messages.to_a.reverse,

Whereas in the message mover I am ordering by created_at to maintain order, which could cause some small discrepancies:

github.com/discourse/discourse-chat

lib/message_mover.rb

82c0ee7f1


      
          def find_messages(message_ids, channel)
            ChatMessage.where(id: message_ids, chat_channel_id: channel.id).order(:created_at)
          end

I have some ideas on how we might be able to address this (maybe changing the message mover to order by ID or changing the controller to order by created_at would be enough, preferring the latter because I think it would make more sense), but I would like to hear just how messed up the order is if it’s possible to tell.

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Moving chat messages to a new channel jumbled them all up

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