Re: index usage

Hello,

I would start by gathering some concrete metrics on your query.

There are several rules of thumb regarding when and when not to use an index. I typically fire up SQL*Plus, set autotrace on, and then perform the query that's of interest. My goal is to bring the number of consistent gets down, and of course, the time it takes to run the query. If the number of consistent gets decreases after creating an index, the optimizer is most probably taking advantage of it. You'll know for sure by looking at its explain plan. Apart from that, it's equally important to look at the query itself, as many times in my experience, the performance suffered because of the way I wrote the query.

Good luck, and let me know how things go.

Regards,
Arun

hastenthunder wrote:
> Hello,
>
> I've read many documentations online stating to only create an index
if
> queries against this table frequently retrieve less than 15% of the
rows.
> However, if the query returns, say, 40% of the rows, wouldn't
indexing the
> column still help by cutting the work by roughly half?
>
>
> hastenthunder
Received on Wed Jan 19 2005 - 09:57:39 CST