[WALoeIII]

This is very useful for batch or cleanup jobs.

For example, imagine a system where items are soft-deleted immediately upon user action, but not actually deleted for a few days to facilitate restoration (recycle bin).

There is going to be some nightly/hourly/scheduled job that actually really deletes these records. Initially it will have little work to do, but over time as the system grows it may become slow. Typically this would be hard to separate from other slow queries, you would have to catch it running while causing other queries to pile up. Query time isn't necessarily useful here as you may have enough I/O to cover the slow query replacing pages in the cache, but that I/O would be better serving user facing requests instead of this cleanup job.

This feature allows for the "work" it really takes to serve the query to cause it to error, instead of time which may grind down for other reasons. At this point you know its time to re-think the soft-deletion strategy, you disable the job. Maybe you sweep more frequently? Maybe you keep a look-aside of things to sweep to avoid scans? Maybe you sweep during a low-traffic time? Whatever. It buys you time to think.

I wish there were something comparable for MySQL.