[oracle-l] Re: Index block count
- From: "Jonathan Lewis" <jonathan@xxxxxxxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Tue, 27 Jan 2004 21:35:07 -0000
What are you checking to see the "block" count ?
v$sess_io
v$sesstat
trace file ?
You've obviously set up a repeatable test, why
not send us the output so that we can see the
actual figures, and the execution plan.
By the way, if the blevel is two, then an index-only
query would have to hit at least three blocks:
root, branch, and leaf.
The blevel is the number of branch levels, and the
height is blevel plus one.
Regards
Jonathan Lewis
http://www.jlcomp.demon.co.uk
The educated person is not the person
who can answer the questions, but the
person who can question the answers -- T. Schick Jr
Next public appearances:
Jan 29th 2004 UKOUG Unix SIG - v$ and x$
March 2004 Hotsos Symposium - The Burden of Proof
March 2004 Charlotte NC OUG - CBO Tutorial
April 2004 Iceland
One-day tutorials:
http://www.jlcomp.demon.co.uk/tutorial.html
Three-day seminar:
see http://www.jlcomp.demon.co.uk/seminar.html
____UK___February
____UK___June
The Co-operative Oracle Users' FAQ
http://www.jlcomp.demon.co.uk/faq/ind_faq.html
----- Original Message -----
From: "Terrian, Tom (Contractor) (DAASC)" <Tom.Terrian@xxxxxxx>
To: <oracle-l@xxxxxxxxxxxxx>
Sent: Tuesday, January 27, 2004 9:08 PM
Subject: [oracle-l] Index block count
I have a b-tree, unique, local, prefixed, range partitioned index. The
blevel
on all of the partitions is 2. There are no chained/migrated rows in the
table.
I have a query that selects 1 record and only uses the index. I am not sure
why
the query uses 4 blocks. I would think that it would just have to use 1 for
the
branch block and 1 for the leaf block. Can someone explain it to me? (I
have
run the query 8,000 times and the average blocks per execution is 4.1)
Thanks,
Tom
-------------------------------------------------------------
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-------------------------------------------------------------
To unsubscribe send email to: oracle-l-request@xxxxxxxxxxxxx
put 'unsubscribe' in the subject line.
-------------------------------------------------------------
-------------------------------------------------------------
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-------------------------------------------------------------
To unsubscribe send email to: oracle-l-request@xxxxxxxxxxxxx
put 'unsubscribe' in the subject line.
-------------------------------------------------------------
Other related posts:
