Dynamic named sets in AS2008 - not as fun as you might think
I got all excited when, last summer, Mosha blogged about dynamic named sets in Katmai: just when it looked like there weren't going to be any cool new features to play with in AS2008, here was a juicy new MDX thing. However I didn't really play with them properly until a bit later when I came to prepare my presentation for last autumn's SQLBits conference, and that's when I realised that they weren't quite as cool or useful as I had thought they were going to be.
The key thing I hadn't picked up on from my initial reading of Mosha's blog entry was that they are evaluated once per query. While that means they are still useful in some scenarios, one of the key examples that Mosha describes in his blog entry is a bit misleading and that's the ranking example. We all know, or at least we should all know, that the key to optimising rank calculations is to declare a named set which gets ordered just once and which is referenced inside the calculated member that returns the rank. Mosha accurately points out that the big drawback to this approach is that "It can only be used when the user can write his own MDX query" but then says that dynamic named sets are a solution - and my point here is that, in my opinion, they aren't really.
Tags: set