Re: Help with composite indices

Irwin Goldstein wrote: > > Check out http://www.objectsoft.com (shameless plug) for a > script which automatically performs an appropriate sequence > of UPDATE STATISTICS commands for specified tables. > This script is great, but it doesn't reflect the latest recommendations from Informix (for ODS 7.10.UD1 onward). These are (summarised): 1. Run UPDATE STATISTICS MEDIUM DISTRIBUTIONS ONLY for each table or for the entire database 2. Run UPDATE STATISTICS HIGH DISTRIBUTIONS ONLY for: - lead key in every index - join columns - columns frequently accesses via an equality filter - the first column to distinguish a composite index from other composite indexes on a table, and all columns preceeding it 3. Run UPDATE STATISTICS LOW for the database Note, a lot of this is to reduce the time taken to update the statistics, not to improve query performance. Peter Whittleton (whittle@ssax.com)