Re: update statistics not recommended!

In article <35D46A64.2BFB@netcomuk.co.uk>, ntruby@netcomuk.co.uk says... >My new site has a third-party financial package (Lawsons), running on >v7.13. The underlying DBMS is Informix. The Lawsons help desk has told >me that they recommend that we never run UPDATE STATISTICS, as it will >degrade performance. Their reasoning, allegedly based on empirical >evidence of their users, is that all their SQL is written with where >clauses, and the indexes that exist will be used, which is what is >required. How do they control what indexes are going to be used anyway? Generally, all SQL is written with "where" clauses, and at least in Informix 7.13 you have no control over what index it selects. (You can sorta persuade it with persuasive use of columns in your where clause.) We use software originally developed under Informix 3.3, where you did select specific indexes to use. This software was later ported to Informix SQL and converted into SQL. We've found that frequent update statistics makes most of our queries run faster; the more information the optimizer has, the better it can tell which indexes to use. No update statistics at all means that for us, at least, the engine often chooses incorrect indexes and (sometimes) wildly inappropriate sequential searches. In short, I think Lawsons is out of their mind. :-) -- William Harris william@carsinfo.com Check out the NAGS spam filter. http://www.nags.org