Re: leaf node 90-10 splits

The failure to do the 90/10 split is a bug (it worked properly in 8.1) which is currently being investigated. I can't remember the number, but I passed it to Oracle some time ago.

As to the original question - no idea, 100/0 seems to be the correct strategy; however, there was an earlier version of Oracle where I did some tests that showed Oracle doing block splits which whose position seemed to be affected by the relative position of the new entry in the block. But I can't find the tests, and I now wonder if it was just the special split to optimise branch compression that Steve Adams worked out a little while ago.

Regards

Jonathan Lewis
http://www.jlcomp.demon.co.uk

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• Original Message ----- To: "Multiple recipients of list ORACLE-L" <ORACLE-L_at_fatcity.com> Sent: Wednesday, December 10, 2003 9:24 PM

> Hi!
>
> SQL> select * From v$sysstat where name like '%split%';
>
> STATISTIC# NAME
> CLASS VALUE
> ---------- ---------------------------------------------------------------
-
> ---------- ----------
> 195 leaf node splits
> 128 612
> 196 leaf node 90-10 splits
> 128 209
> 197 branch node splits
> 128 3
>
> I did a little test few days ago (using stats & treedumps):
>
> If you insert an equal or larger key to the current max value in a full
leaf
> block *within the transaction which filled the block*, just a new leaf
block
> is added to index and "leaf node 90-10 splits" statistic is incremented.
If
> you commit in the meantime, before "overflowing" the block, then the leaf
> block is split 50-50 and "leaf node splits" stat is incremented.
> So, Oracle 9.2 cares about transactions as well, in addition to checking
key
> values...
>
> Tanel.
>

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Author: Jonathan Lewis
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