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Re: index rebuilding...

From: Howard J. Rogers <howardjr2000_at_yahoo.com.au>
Date: Sat, 1 Feb 2003 04:52:37 +1100
Message-ID: <6By_9.37587$jM5.94689@newsfeeds.bigpond.com>

"DA Morgan" <damorgan_at_exesolutions.com> wrote in message
> I never thought I'd ever try to correct you but I believe (sticking it
> way out there on ths one) it is possible for there to be four on one and
> three on the other from time-to-time as Oracle doesn't rebalance every
> time someone performs a single insert or delete. Isn't it more a case of
> never having 5 and 3?

Jonathan can answer for himself, of course. But I'll take a stab at it too... no, it's not possible for a single insert to result in an unbalanced index. Oracle's indexes are *always* balanced. That's why you really don't want to create indexes unnecessarily, because they can slow down simple DML on the table dramatically. Your simple insert that threatens to unbalance an index will cause a whole raft of cascading adjustments to the index structure precisely to avoid imbalance.

I don't know whether it's just a myth or not, but Oracle refers to its indexes as "B*Tree" structures, not 'b-tree' ones. And that's because the 'b' doesn't stand for 'binary', but 'balanced'.

Whether that bit of apocrypha is true or not, Oracle index structures are always re-balanced.

Regards
HJR Received on Fri Jan 31 2003 - 11:52:37 CST

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