A couple of months ago, I discovered in a (not so well maintained) database a totally useless table containing 430 million unindexed rows, growing by about 80 000 rows per day.

It was a top candidate for removal. However, I never got the opportunity to achieve this (a.k.a. not the priority). I did not even have the opportunity to try to delete it in a weekly refreshed dev database.

I was wondering whether a simple TRUNCATE or DROP could ever be very time-consuming? I mean, could this operation block a production environment for several minute like DELETEs can when they are not well written. Or are these safe operations?