Re: Query Optimizer

Posted in 1998

KPonn — 1 Feb 1998 05:10:57 GMT — source: Informix-list mailing list archive (1991-1998)

>Help me please! >I need information about algorithm of Query Optimizer. >Informix Engine - OnLine Dynamic Server 7.10 One can write a book on this topic. Basically, the optimizer looks at all possible ways of scanning every table in a query. The cost for each path is calculated using the formula: cost = CPU cost * Wt factor + I/O cost, where Wt factor is 0.03. Cheapest path will be chosen. Also, OPTCOMPIND environment variable (0,1, or 2) determines how the optimizer acts. Hope this helps. Keith P