I feel I should stress that pretty much everything you guys have said on this thread so far has been accurate; the problem we are dealing with here is the optimizer making what looks like the right choice from its point of view, but which turns out to be highly suboptimal because it doesn't have good information to base its choices on, and the model it uses is a very general-purpose affair. The obvious solution has already been suggested - provide an obvious best-choice (covering) index. The alternative is to create better statistics, or to accept the out-of-model condition and use an index hint. So, overall, I'm just adding extra analysis around the points already made in case it is of interest to Roger.