[oracle-l] Re: Index block count
- From: Joze Senegacnik <JozeS@xxxxxxxxxxxxxx>
- To: "'oracle-l@xxxxxxxxxxxxx'" <oracle-l@xxxxxxxxxxxxx>
- Date: Tue, 27 Jan 2004 22:24:50 +0100
Tom,
obviously there are many deleted entries in your index. Probably the index
key is updated frequently. Recently I made a some tests on a table with only
one row and I created an index with all columns. Without index access
reading one row from one block took constantly 7 LIO. When using index
access I reduced it to 1 block as supposed. But after 1000 updates the LIO
was 48 blocks (only index scan). Maybe this explains also your case.
Regards, Joze
-----Original Message-----
From: Terrian, Tom (Contractor) (DAASC) [mailto:Tom.Terrian@xxxxxxx]
Sent: Tuesday, January 27, 2004 10:08 PM
To: 'oracle-l@xxxxxxxxxxxxx'
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
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