Re: Update Statistics - 7.23

Mark Taylor wrote: > > Hi, > > We are looking for input on running Update Statistics on some reasonably > large tables (approximately 80 million rows) and are looking for a > combination of reasonable speed and reasonably accruate results. We > have the methods in the Informix Documentation and are not getting the > results we need. Anybody have any suggestions. The DBs are 7.23 on Sun > Solaris 2.5 platform. What do you mean you are not getting the results that you need. Comared to 5.0x? Compared to what? What are your needs? Need to force the server to not sort? What? In general the recommendations in the release notes file SERVERS_7.2 are the most up to date and are USUALLY good enough. However, the 7.2x optimizer is MUCH smarter than the 5.0x optimizer (and even improved over the optimizer in 7.1x) and will often decide that, based on the statistics and distributions, using a different index and sorting will fetch the total select set more quickly and it is usually correct. If you, rather, need the first few rows quickly this can be death. When this is the case sometimes updating statistics HIGH on all columns helps but usually you will have to drop distributions and update statistics LOW so that the optimizer behaves like the 5.0x optimizer did. Please give us more details and someone will try to help. Art S. Kagel