To Sort Or Not To Sort

We are using a modeling technique called Anchor Modeling in our data warehouses. You can read more about the technique itself at our homepage http://www.intellibis.se, where we have published a fact sheet and a recently held presentation (TDWI European conference). One of the features with this technique is its simple way to historize data. This is done by having a fromDate column which together with the surrogate key will yield a unique combination. On the tables that has this kind of historization we add a primary key, which in turn will create a clustered index, with the following specification (surrogateKey asc, fromDate desc). This will physically order data on the storage media according to the specificed columns and ordering. Now I move on to create a "latest view" of this table which does a subselect to find the latest version for every surrogateKey using max(fromDate). Should not the optimizer now figure out that data is ordered so that the latest version always comes first for every surrogateKey, hence any sorting would be unneccessary? If I look at the actual execution plan after running a query that uses the view there is a sort in the plan, but the cost is always 0%. Does this mean that it did not sort the data, or that it did call a sorting routine, but it actually took very little time to do the sorting? If so, is there a reason that is has to do the sorting or could it have been left out by an even smarter optimizer?

I would also like to applaud the people behind the optimizer, since it will figure out which tables are in fact necessary to query and eliminate others, even if I have left joined them into the view I am using. This speeds up performance and makes anchor modeling feasible. Unfortunately optimizers from other vendors seem to have trouble doing this...

Regards,
Lars