feat: adds indexes with id for chat history query ordering

[drizco]

this adds the id column in aichat_events table to the indexes used in the chat history query to help with ordering the chats. we were getting a mysql error saying the sort memory ran out, and while the actual issue is with the hidden context being way too large, it made sense to add these indexes to optimize sorting chat history in the future. we might also want to extract just the json values we need rather than sending hidden context over the wire, but that will happen in follow up work.

Links

• Jira: https://codedotorg.atlassian.net/browse/TEACHING-48

Testing story

Deployment strategy

Follow-up work

• remove the indexes that don't have id
• select just the values desired in the chat_history query, excluding hiddenContext

Privacy

Security

Caching

PR Creation Checklist:

• Tests provide adequate coverage
• Privacy impacts have been documented
• Security impacts have been documented
• Code is well-commented
• New features are translatable or updates will not break translations
• Relevant documentation has been added or updated
• User impact is well-understood and desirable
• Follow-up work items (including potential tech debt) are tracked and linked

[Erin007]

Code changes look good! I'm pretty sure the table is small enough (comparatively) that is should be completely fine, but wondering if there's a risk of the table locking and causing any issue when the migration hits production?

[drizco]

Code changes look good! I'm pretty sure the table is small enough (comparatively) that is should be completely fine, but wondering if there's a risk of the table locking and causing any issue when the migration hits production?

should be fine, the indexes can be added in place without locking the table. it's a little slower but worth it! 😅

edit: I guess it doesn't guarantee not to lock, but it should be less disruptive and allows concurrent reads/writes