frequency + height based histograms.
- From: "The Human Fly" <sjaffarhussain@xxxxxxxxx>
- To: oracle-l <oracle-l@xxxxxxxxxxxxx>
- Date: Mon, 6 Mar 2006 11:59:03 +0300
Hello list,
I was reading Jonathan's great book, at least for me, 'CBO
Fundamentals' and I got confused of frequency/height based histograms,
though he explained in a great way.
What I understood is that, if we have more than 254 distinct values in
a columns, we use height based histograms and when we have less than
254 distinct values in a column, we use one bucket for 1 distinct
value. Are my assumption are correct, or am I missing something?
I did a small test on 9207 database where a column has only two
distinct values and I try to create 2 buckets (for columns size 2
columns name). When I look at the user_tab_histograms, the
endpoint_number 1 and 2. When I change the size from 2 to 3, I get the
accurate endpoint_number.
Thanks for your time.
--
Best Regards,
Syed Jaffar Hussain
8i,9i & 10g, OCP DBA
Banque Saudi Fransi,
Saudi Arabia
http://jaffardba.blogspot.com/
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