Communication: Speedup messaging

[lennart-keller]

Checklist

General

• I tested all changes and their related features with all corresponding user types on a test server.
• This is a small issue that I tested locally and was confirmed by another developer on a test server.
• Language: I followed the guidelines for inclusive, diversity-sensitive, and appreciative language.
• I chose a title conforming to the naming conventions for pull requests.

Server

• Important: I implemented the changes with a very good performance and prevented too many (unnecessary) database calls.
• I followed the coding and design guidelines.
• I documented the Java code using JavaDoc style.

Motivation and Context

The query for retrieving recipients for WebSocket messages takes too much time on production systems.

Description

The query does not return the whole user anymore. Additionally, the join with the course table has been removed.

Steps for Testing

Prerequisites:

• 2 Students
• 1 Course with messaging enabled

1. Write messages in the on the messaging page, a lecture details page, and an exercise details page as student 1 in channels, group chats and direct chats that both students are a member of
2. Student 1 should see the message without much delay
3. Student 2 should see a notification (if not on the same page as student 1) or the message without much delay if they have opened the conversation.
4. Student 2 does not receive duplicate notifications if mentioned
5. If student 1 writes in a channel or group chat that student 2 isn't a member of, student 2 does not receive notifications

Review Progress

Performance Review

• I (as a reviewer) confirm that the server changes (in particular related to database calls) are implemented with a very good performance

Code Review

• Code Review 1
• Code Review 2

Manual Tests

• Test 1
• Test 2

Test Coverage

Screenshots

No UI Changes

[MaximilianAnzinger]

Code lgtm
Manually tested on TS2

[basak-akan]

Tested in testing session on TS2 worked as described, message delay reduced.

[rstief]

Tested in testing session (ts2)