Updating `last_activity_at` and `pushes_since_gc` on every push can block the database
Customer issue: https://gitlab.zendesk.com/agent/tickets/19704
When there are many Sidekiq tasks backlogged, each push event causes two columns to be updated:
last_activity_atpushes_since_gc
This can hammer the database to the point where the rate at which these locks get resolved is slower than the rate at which new locks are inserted. Part of the problem is that the index to last_activity_at also gets updated each time this column changes.
The temporary solution is to disable updates to these columns.
We need a more performant solution here. For example, we may only want to update these columns every 60 seconds for each project.
/cc: @jnijhof, @dzaporozhets, @dblessing