Apache Druid

It has one, but very basic -- looks at things more like "is there a filter", "is there a join", and "is there a subquery" rather than the specific filters and functions involved

I wonder if you can get what you're looking for using query priorities or timeouts?

`query priorities or timeouts` ? I am not sure I follow, custom timeout for every user? I don’t know about query priorities as well.

I was wondering if you knew, a priori, certain users are the ones that tend to perform "unsavory" queries

If you do then you can run those at lower priority or with shorter timeouts

If it could be _any_ user then my suggestion isn't as useful

well… we do know, after the fact, the usernames of these unsavory queries because we processed the request logs.