Here’s the Connect Item involved – written by Michael Swart.
Trace flag 2390 can cause large compile time when dealing with filtered indexes. (Active)
Huh. “What does that have to do with clustered columnstore indexes?” you might ask. No, really, it’d be a personal favor if you *did* ask…
Ask and then read on. This is the kind of post I’d send to someone wanting to learn how to troubleshoot issues.