I can’t tell you how tempted I was to call this MAXTOP. Thinking about it still causes stray giggles to bubble up, as I gleefully envision sharing this info with eager young DBAs at a SQL Saturday, then ushering them off to a session on parallelism. Thankfully I’m not that evil.
The real conclusion is that SQL Server is programmed to be very clever. Despite the cleverness though, details matter, and the cleverness often falls short. What’s that warm glow I feel inside? Ah yes, job security.
Definitely worth a read, and Forrest also shares the repro scripts.