RE: Index height
- From: Jonathan Lewis <jonathan@xxxxxxxxxxxxxxxxxx>
- To: "oracle-l@xxxxxxxxxxxxx" <oracle-l@xxxxxxxxxxxxx>
- Date: Sat, 26 Apr 2014 07:34:02 +0000
Here's a note I wrote a few years ago about B-tree indexes and the arithmetic
of work/height: http://jonathanlewis.wordpress.com/2007/03/18/thinking-big/
If your indexes are designed correctly, and ignoring a couple of pathological
cases and bugs, a B-tree index (with NO regular maintenance) should probably be
able to cover 10M to 30M rows at height = 3; and at height 4 that could
increase to somewhere between 1 and 5 billion rows.
Bitmap indexes are harder to predict, but generally small - unless you're doing
regular DML in small batches in which case you can be very unlucky
Regards
Jonathan Lewis
http://jonathanlewis.wordpress.com
@jloracle
________________________________
From: oracle-l-bounce@xxxxxxxxxxxxx [oracle-l-bounce@xxxxxxxxxxxxx] on behalf
of Orlando L [oralrnr@xxxxxxxxx]
Sent: 26 April 2014 05:24
To: oracle-l@xxxxxxxxxxxxx
Subject: Index height
List
I decided to check the height of indexes used in our databases as part of my
learning experience. In the biggest OLTP database (550 GB) that I maintain I
saw about a 100 indexes with height of 4 (3 blvl+1), a 1000 with height 3.
I was expecting some big bad 'heights' for indexes. Do the listers have big
indexes lurking in their neck of the woods?
Thank you all
Orlando
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