Poor performance with Histogram
- From: "Shivaswamy Raghunath" <shivaswamykr@xxxxxxxxx>
- To: ORACLE-L <oracle-l@xxxxxxxxxxxxx>
- Date: Mon, 11 Dec 2006 10:39:20 -0500
Hello listers.
I have used histograms to imporve performance drastically on several earlier
occassions on our DSS databases. But recently, it took me quite a while to
determine that by removing histograms, I am able to run one critical query -
the report from which was happened to be of interest to my CEO - far faster
than with histogram. The test query - involving two tables, one
partitioned(60 Million) and another regular (13 Million), with outer joins,
view merging, few aggregate sorts and sub queries- completes in under 5 sec
without histograms while it takes nearly 17 minutes with histograms.
Can you tell me where I can look to understand this. Plans are different, of
course. But how CBO fails to evaluate the plan I could not comprehend. I am
in the process of studying Jonathan Lewis (Chapter 7 & 14) to understand.
But any input/insight would greatly be appreciated.
Thanks,
Shiva
Other related posts:
