fix(migrations): Fix DoesNotExist exception handling in migration 0024

[BYK]

Reported here: forum.sentry.io/t/error-importing-events-during-upgrade-from-9-1-2-to-20-11-and-up/12683/6?u=byk. I think this is either related to a Django upgrade or a Python upgrade. We have change the code to be more efficient and clever now that we don't even need the error handling there.

[beezz]

Doesn't that actually mean that e.group_id is None?

[iProgramStuff]

Yeah, I think it does. Might be able to just check on that before setting group.

[BYK]

Are you sure this is the only case? What if they have an invalid group id set, which is entirely possible?

[wedamija]

This migration is a bit tricky in general since it uses so many external functions.

I think what I'd do here instead would be group = Group.objects.get(id=event.group_id) and not import NewGroup at all. The logic in Event.group really just handles caching which isn't going to be a thing here. We could also check that group_id is not None before making the query.

You'll also need to use group down below on insert, rather than event.group.

Edit: Actually, reading this more we do actually use event.group for caching, we fetch it in advance in _attach_related. The issue here is that if the group didn't exist, then we actually make another database query to try and fetch it again, then throw NewGroup.DoesNotExist.

What we should actually do is set event.group = e.group, then we'll be fine. We already fetched it from the database above, so there's no need to do this check again. We can then totally remove this try/catch, and only use event.group. Then we don't need to import NewGroup at all, and we should actually speed this migration up a bit, since we're not double fetching all groups.

Might also be worth setting event.project = e.project, since that caching also gets dropped when we create event

[BYK]

@wedamija updated based on your suggestions. Rereview? <3

[github-actions]

This PR has a migration; here is the generated SQL

BEGIN;
--
-- MIGRATION NOW PERFORMS OPERATION THAT CANNOT BE WRITTEN AS SQL:
-- Raw Python operation
--
COMMIT;

[iProgramStuff]

This looks fine to me.

[iProgramStuff]

Yeah, I think it does. Might be able to just check on that before setting group.