frequency + height based histograms.

From: The Human Fly <sjaffarhussain_at_gmail.com>
Date: Mon, 6 Mar 2006 11:59:03 +0300
Message-ID: <97b7fd2f0603060059h302e3da3j20f221ece96f2c68@mail.gmail.com>

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.

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Best Regards,
Syed Jaffar Hussain
8i,9i & 10g, OCP DBA
Banque Saudi Fransi,
Saudi Arabia
http://jaffardba.blogspot.com/

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"Winners don't do different things. They do things differently."
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http://www.freelists.org/webpage/oracle-l Received on Mon Mar 06 2006 - 02:59:03 CST