is automatically monitoring progress impossible?

[Anton Kratz]

I think it would be great to have some kind of progress bar for long-running mySQL commands.

So if I enter a command that takes many hours to run, mySQL would
1) realize that this command takes a long time to execute
2) make an estimate HOW long it will take (to know what 100%) is
3) check what the current progress is

1 + 2 + 3 -> progress bar is possible

The only page i found dealing with this issue is this attempt at a progress bar patch: http://jcole.us/blog/archives/2007/02/08/progress-in-mysql-process-list/

My question is, is this possible or why is it not implemented? I mean, is it is not possible, because in priciple we can't compute the duration to execute the command? Or is it possible in principle but just not considered important enough to implement it in mySQL?

I think it would be very useful, especially for long running alter table statements or queries asking over a range of values. Often I execute a command and have no idea how long I will have to wait (a few more hours? or even days?)

Also, are there database systems other than mySQL maybe which do have such a feature implemented?