Yes, I'd agree, but a fair number of database's wire protocols have no means of saying "this request is cancelled"!

As for "if the requester goes away", remember that the requester might be a few hops away. E.g., the HTTP connection from the mobile client drops; the web server and its connection to the DB is still alive and well. I can forcefully shut that connection, but that's somewhat of a drag (I'd rather keep it open, since it is perfectly good).

Beyond closing the connection, and being able to issue some form of "cancel this query" request: HTTP/1 lacks it entirely, PostgreSQL requires opening a separate connection, Redis lacks it entirely, and I think both Mongo and MySQL lack it entirely.

Even support for "time this request out" is spotty.