Re: Histogram worthwhile?
- From: Hemant K Chitale <hkchital@xxxxxxxxxxxxxx>
- To: roberto_veiga@xxxxxxxxx
- Date: Tue, 24 Feb 2009 22:30:32 +0800
I have two Blog Posts on Bind Variable Peeking and Histograms :
http://hemantoracledba.blogspot.com/2008/07/bind-variable-peeking.html
and
http://hemantoracledba.blogspot.com/2007/09/more-on-bind-variable-peeking-and.html
(pointing to Tom Kyte's articles)
Hemant K Chitale
http://hemantoracledba.blogspot.com
At 10:01 PM Tuesday, Roberto Veiga wrote:
We have another performance problem to solve. The performance that
was good, now is bad. Very bad with an unacceptable performance and
nobody makes any changes to the system. Nor the analyst neither the
dba. Why the performance is not ok anymore?
<deleted>
I dont know if this is a problem or if it is just a optimizer's
behavior, but I am doing a research to find some alternatives to
this problem. And I find some (thanks Tom Kyte):
.use bind variables but dont use histograms. so the plan is going to
be the same for every single execution. one size fits all approach
.dont use bind variables but use histograms. so the optimizer will
evaluate the plan every execution and discover the best plan
.use bind variables, use histogram but change the code. if the value
is in this range, execute this query. if not, execute another query.
i need to know distribution data. using the width_bucket function
could be a good way to discover how is the distribution
Anyone have another idea?
Thanks
Veiga
--
//www.freelists.org/webpage/oracle-l
Other related posts:
