Re bitmap index

From: Gary Waldrom <garyw_at_amonra-insight.com>
Date: Wed, 24 Nov 1999 12:23:33 -0000
Message-ID: <E47927FC0A9CD3119D090000216DAFF5A99F@THOTH>

From experience you should only be looking at a bitmapped index if your cardinality ratio is lower that 1:20000

i.e. if you have a table with people in it and you store a Gender flag of 'M' and 'F' you would need approx 40,000 rows before this becomes in any way efficient

Gazza

-----Original Message-----
From: -=< a q u a b u b b l e >=-
[mailto:aquabubble_at_Remove.No.Parma.Ham.Remove.geocities.com] Posted At: 23 November 1999 14:40
Posted To: server
Conversation: bitmap index
Subject: Re: bitmap index

Norris <jcheong_at_cooper.com.hk> wrote in message news:81dnrc$1mjc$1_at_adenine.netfront.net...
> What is low cardinality?

Not very many distinct values in a column for all of your rows. Received on Wed Nov 24 1999 - 06:23:33 CST