Message-Id: <10526.108827@fatcity.com> From: "Rachel Carmichael" Date: Tue, 13 Jun 2000 02:41:40 GMT Subject: Re: METALINK and OWS Oh, and I once had a query go from 30 minutes to 6 minutes by dropping an index.... >From: Regina Harter >Reply-To: ORACLE-L@fatcity.com >To: Multiple recipients of list ORACLE-L >Subject: Re: METALINK and OWS >Date: Mon, 12 Jun 2000 10:51:04 -0800 > >I hate to dispute this, and I really can't support it except by the result, >but I just improved the performance of a query which selected almost 40% of >the rows by ADDING an index (on 8.0.6). > >Regina >Camarillo, California > >At 04:14 PM 6/11/00 -0800, you wrote: >>WHOA! Slow down before you drop the indexes. Indexes are not totally >>useless! It very much depends on the queries you run against your >>database. If you are doing a mixture of queries, where some return single >>rows or a very small subset of data, and some return a large number of >>rows, you still should keep the indexes for the first type of query. >> >>Rachel >> >> >>>From: Nicholas Tufar >>>Reply-To: ORACLE-L@fatcity.com >>>To: Multiple recipients of list ORACLE-L >>>Subject: Re: METALINK and OWS >>>Date: Sun, 11 Jun 2000 14:17:51 -0800 >>> >>> > >>> > Nicholas, >>> > >>> > Sorry... I thought most people knew this. Oracle says that if a query >>>will >>> > return more than 20% of the rows of a table, it will use a full table >>>scan. >>> > So you DON'T tune it to use an index. In fact, as of 8i, I believe >>>Oracle >>> > now recommends that if a query returns as little as 3-5% of a table, a >>>full >>> > table scan is the way to go. >>> >>>A very valuable piece of information. How did I miss it! >>>Now I know what I am going to do on Monday. I had a feeling that >>>all those indeces are useless, now I know why they are. >>>Thank you very much. >>> >>>Nicholas >>>-- >>>Author: Nicholas Tufar >>> INET: ntufar@chemist.gen.tr >>> >>>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@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). >> >>________________________________________________________________________ >>Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com >> >>-- >>Author: Rachel Carmichael >> INET: carmichr@hotmail.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@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). > >-- >Author: Regina Harter > INET: rharter@emc-inc.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@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). ________________________________________________________________________