Re: Update Statistics Low, Medium & High

billy@west.co.za (Billy Wheeler) wrote: :> >In our system, we discover sometimes some tables in index searching is much :> >faster while we update their statistics low or medium instead of high. :> I heard a discussion the other day which indicated that when you update :> statistics "high" it causes the optimizer to evaluate every possible query :> path. This evaluation might take longer than the actual query--it depends :> on the indexes and the query. On the "medium" or "low" settings the optimizer :> evaluates only the most likely paths, and chooses one quickly. Though I could :> not find a definitive explanation of this exact point in the documentation, :> a picture might look like: :Am I missing something here? Aren't we supposed to be talking about SET :OPTIMIZATION {HIGH | LOW}? :UPDATE STATISTICS creates (inter alia) data distributions. I don't think it :forces the optimiser to do anything with them... SET OPTIMIZATION forces the :optimiser to consider every query path or not. :Probably wrong again... <sigh> Well Billy, even if you SET OPTIMIZATION HIGH there is a limit to what the optimizer can do if you haven't done UPDATE STATISTICS HIGH. So both should be taken into account. Nils.Myklebust@ccmail.telemax.no NM Data AS, P.O.Box 9090 Gronland, N-0133 Oslo, Norway My opinions are those of my company