Prevent stale reactions when usernames change or users are deleted

[mossae]

Description

While reviewing the reaction implementation, I noticed that reactions are currently stored using usernames directly inside the message document.

For example, in setReaction a reaction entry is created as:

message.reactions[reaction] = { usernames: [], };

and the reacting user is stored like this:

message.reactions[reaction].usernames.push(user.username)

Because reactions reference usernames rather than userIds, this can lead to stale data in a few scenarios:

If a user changes their username, existing reactions still reference the old username.

If a user deletes their account, the username may remain in the message’s reaction list.

In both cases, the message document may end up referencing users that no longer exist or have changed identity.

Potential Improvement

A full redesign of the reaction schema would likely require a migration across all message documents, which may not be desirable for large deployments.

However, a smaller incremental improvement could improve correctness while keeping the current structure compatible.

Possible steps:

1. Store userId alongside username for new reactions.

Example:

message.reactions[reaction] = { usernames: [], userIds: [], }

2. When a username is changed, update reaction usernames by matching the stored userId.

3. When a user account is deleted, remove their reactions from messages using the stored userId.

This would allow improving reaction consistency while maintaining compatibility with existing message documents.

Related Discussion

Related: #20425

Contribution

If this aligns with the current architecture, I’d be happy to start with a small improvement (for example storing userId alongside username for new reactions) and iterate from there.

[kushkumarkashyap7280]

right .. userid is more stable than username ... i would like to work on this issue but .. why need to add username i think changing username [] to userids [] is best idea since we can get username current username based on that userid even user change it later

for performance your idea is very good to store both .. but if we want that previous message appear updated username reaction so must store just userids [] ... but now i m moving to hybrid approach

[mossae]

right .. userid is more stable than username ... i would like to work on this issue but .. why need to add username i think changing username [] to userids [] is best idea since we can get username current username based on that userid even user change it later

for performance your idea is very good to store both .. but if we want that previous message appear updated username reaction so must store just userids [] ... but now i m moving to hybrid approach

Thanks for the thoughts! The hybrid approach (storing both userId and username) is actually what I was proposing in the issue to keep reactions stable while avoiding extra lookups.

I’ve already started working on it and will be opening a few incremental PRs shortly.

[mossae]

@sampaiodiego @ricardogarim I would really appreciate your feedback on this approach.
Thanks!

[kushkumarkashyap7280]

suggestion : for integrity you should also update username to current username for example .. if my username is kush123 and i gave reaction now my id and username saved ... but after 6 months i changed my username and came back to that message .. expected behaviour should like my currrent username KushKumar should appear instead of previous username.. means ensure sync integrity too

[mossae]

suggestion : for integrity you should also update username to current username for example .. if my username is kush123 and i gave reaction now my id and username saved ... but after 6 months i changed my username and came back to that message .. expected behaviour should like my currrent username KushKumar should appear instead of previous username.. means ensure sync integrity too

Noted, thanks for pointing that out!