If we know something is going to take a long time, we usually do warn you, or give you the opportunity to cancel it. What you found is either a bug or some long running query. How can we warn you if you are about to experience a bug? No software does that.
If you can tell me steps to reproduce it or get me a call stack as described below, I'll fix it if I can.
To diagnose, follow these steps to turn on freeze detection , and post the output here.