Remove num_watches column from table repository

[lunny]

To keep consistent, a cron job will run in the background to check num_watches. For a big instance, it will become very slow. So I think we can remove the column and query the table when necessary.

[delvh]

and query the table when necessary

Erm… isn't that
?

If yes, this won't be a performance improvement.
It will instead worsen the performance.

[lunny]

and query the table when necessary

Erm… isn't that ?

If yes, this won't be a performance improvement. It will instead worsen the performance.

Yes, but it's a slight additional load. It commonly will only increase by about 1ms for this page. We can also optimize it with cache in future PRs. Why I couldn't do it because introducing cache in this place needs more refactors PR merged first such as #32506 and #32537