Re: A question about Indexing.

From: "Vijith Gunawardhana" <vijith.gunawardhana@wcom.com> > >In my work environment we are using Informix Dynamic Server AD and XP >Options 8.2. > >Here they don't use indexes at all. (Not even primary key indexes) > >1. Is that true if you access more than 15% rows of a table you don't need >any indexes? (What about Group by / Order by?) This is always open to debate, but the reasoning for not having indexes is largely as follows: * If you read more than a certain percentage of rows from a table, indexes aren't used anyway (unless there's a sort). * In general, indexes are beneficial for sorting, but you need to weigh up the performance benefit against the storage cost and the maintenance cost (loads will be substantially slower). It may cost you too much load time to justify the sort benefit. * By the time the data gets into the warehouse, it should be scrubbed and validated, hence the lack of keys for RI. (This is the theory, anyway! :-) >2. Or, is there some thing particular about indexing in this version of >Informix? Not really, the same principles would apply for IDS. >3. What is Informix XPS? Is it different from the above version? XPS is the old name for AD and XP. HTH. ______________________________________________________ Get Your Private, Free Email at http://www.hotmail.com