Thanks Don, Your explanation is very helpful.
- Don Granaman <granaman_at_cox.net> wrote:
> Bitmapped indexes will be fast for the queryagainst
> the 'Y's, but a
> bitmapped index may not be appropriate if you are
> getting lots of DML
> activity on this.
>
> Another option is to use NULL instead of the "vast
> majority" value ('N' - in
> this case) and create an index. The nulls won't be
> indexed, so the index
> will be small. This works best when there are
> relatively few non-majority
> values and they are the ones most
> critically/commonly queried. A hint MAY
> be required to make the CBO use the index. This
> obviousy won't help on
> queries against 'N' though. Example, ORDERS table
> with a STATUS column -
> 98% 'Closed', 2% ('New' | 'Pending' |
> 'Whatever...'). Change the logical to
> interprete NULL as 'Closed' and create an index on
> ORDERS.STATUS. Queries
> for open orders - ('Closed' | 'Pending' |
> 'Whatever...') become very fast.
>
> Don Granaman
> [OraSaurus]
>
> ----- Original Message -----
> To: "Multiple recipients of list ORACLE-L"
> <ORACLE-L_at_fatcity.com>
> Sent: Monday, July 15, 2002 2:58 PM
>
>
> If we have a column of 'Y','N' values, the index
> will
> not help with CBT(usually most of the values are
> 'N').
>
> My question is : how about bitmap indexes? Should it
> help a lot, or just a little bit?
>
> Thanks,
>
> Chris Harvest
>
> __________________________________________________
> Do You Yahoo!?
> Yahoo! Autos - Get free new car price quotes
> http://autos.yahoo.com
> --
> Please see the official ORACLE-L FAQ:
> http://www.orafaq.com
> --
> Author: CC Harvest
> INET: ccharvest_at_yahoo.com
>
> 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: ListGuru_at_fatcity.com (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).
>
> --
> Please see the official ORACLE-L FAQ:
> http://www.orafaq.com
> --
> Author: Don Granaman
> INET: granaman_at_cox.net
>
> 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: ListGuru_at_fatcity.com (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! Autos - Get free new car price quotes
http://autos.yahoo.com
--
Please see the official ORACLE-L FAQ: http://www.orafaq.com
--
Author: CC Harvest
INET: ccharvest_at_yahoo.com
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: ListGuru_at_fatcity.com (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).
Received on Tue Jul 16 2002 - 11:39:23 CDT
