low cardinality -- good candidate for bitmap. little or no updates to the column being indexed -- good candidate for bitmap
"low" cardinality is relative -- 10,000 distinct values in a 300m row table is low, 100 distinct values in a 10K row table might be high but the main criteria I have found is whether or not the column is updated because when you update the values in a bitmap index, it's not just the one row in the index that is updated but the entire segment of the bitmap. And THAT can lock the index on you. Rachel --- Jack Silvey <[EMAIL PROTECTED]> wrote: > Listers, > > We are creating indexes on a 300m row fact table > today. I am researching bitmap versus btree (again) to > see where the latest info points. > > Anyone care to comment on the way to determine whether > an index should be a btree or a bitmap? Anyone even > know a good way to test this? > > thx, > > /jack > > > __________________________________________________ > Do You Yahoo!? > LAUNCH - Your Yahoo! Music Experience > http://launch.yahoo.com > -- > Please see the official ORACLE-L FAQ: http://www.orafaq.com > -- > Author: Jack Silvey > INET: [EMAIL PROTECTED] > > Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 > San Diego, California -- Public Internet access / Mailing > Lists > -------------------------------------------------------------------- > To REMOVE yourself from this mailing list, send an E-Mail message > to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in > the message BODY, include a line containing: UNSUB ORACLE-L > (or the name of mailing list you want to be removed from). You may > also send the HELP command for other information (like subscribing). __________________________________________________ Do You Yahoo!? Yahoo! - Official partner of 2002 FIFA World Cup http://fifaworldcup.yahoo.com -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Rachel Carmichael INET: [EMAIL PROTECTED] Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
