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Home -> Community -> Mailing Lists -> Oracle-L -> RE: METALINK and OWS
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Maybe your new index contained all columns to satisfy your query?
Alex Hillman
-----Original Message-----
From: Regina Harter [mailto:rharter_at_EMC-INC.COM]
Sent: Monday, June 12, 2000 2:51 PM
To: Multiple recipients of list ORACLE-L
Subject: Re: METALINK and OWS
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 <ntufar_at_chemist.gen.tr>
>>Reply-To: ORACLE-L_at_fatcity.com
>>To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com>
>>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_at_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_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).
>
>________________________________________________________________________
>Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com
>
>--
>Author: Rachel Carmichael
> INET: carmichr_at_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_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).
-- Author: Regina Harter INET: rharter_at_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_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). ------_=_NextPart_001_01BFD4C8.CF349250 Content-Type: text/html; charset="iso-8859-1" <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"> <HTML> <HEAD> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1"> <META NAME="Generator" CONTENT="MS Exchange Server version 5.5.2448.0"> <TITLE>RE: METALINK and OWS</TITLE> </HEAD> <BODY> <P><FONT SIZE=2>Maybe your new index contained all columns to satisfy your query?</FONT> </P> <P><FONT SIZE=2>Alex Hillman</FONT> </P> <P><FONT SIZE=2>-----Original Message-----</FONT> <BR><FONT SIZE=2>From: Regina Harter [<A HREF="mailto:rharter_at_EMC-INC.COM">mailto:rharter_at_EMC-INC.COM</A>]</FONT> <BR><FONT SIZE=2>Sent: Monday, June 12, 2000 2:51 PM</FONT> <BR><FONT SIZE=2>To: Multiple recipients of list ORACLE-L</FONT> <BR><FONT SIZE=2>Subject: Re: METALINK and OWS</FONT> </P> <BR> <P><FONT SIZE=2>I hate to dispute this, and I really can't support it except by the result, </FONT> <BR><FONT SIZE=2>but I just improved the performance of a query which selected almost 40% of </FONT> <BR><FONT SIZE=2>the rows by ADDING an index (on 8.0.6).</FONT> </P> <P><FONT SIZE=2>Regina</FONT> <BR><FONT SIZE=2>Camarillo, California</FONT> </P> <P><FONT SIZE=2>At 04:14 PM 6/11/00 -0800, you wrote:</FONT> <BR><FONT SIZE=2>>WHOA! Slow down before you drop the indexes. Indexes are not totally </FONT> <BR><FONT SIZE=2>>useless! It very much depends on the queries you run against your </FONT> <BR><FONT SIZE=2>>database. If you are doing a mixture of queries, where some return single </FONT> <BR><FONT SIZE=2>>rows or a very small subset of data, and some return a large number of </FONT> <BR><FONT SIZE=2>>rows, you still should keep the indexes for the first type of query.</FONT> <BR><FONT SIZE=2>></FONT> <BR><FONT SIZE=2>>Rachel</FONT> <BR><FONT SIZE=2>></FONT> <BR><FONT SIZE=2>></FONT> <BR><FONT SIZE=2>>>From: Nicholas Tufar <ntufar_at_chemist.gen.tr></FONT> <BR><FONT SIZE=2>>>Reply-To: ORACLE-L_at_fatcity.com</FONT> <BR><FONT SIZE=2>>>To: Multiple recipients of list ORACLE-L <ORACLE-L_at_fatcity.com></FONT> <BR><FONT SIZE=2>>>Subject: Re: METALINK and OWS</FONT> <BR><FONT SIZE=2>>>Date: Sun, 11 Jun 2000 14:17:51 -0800</FONT> <BR><FONT SIZE=2>>></FONT> <BR><FONT SIZE=2>>> ></FONT> <BR><FONT SIZE=2>>> > Nicholas,</FONT> <BR><FONT SIZE=2>>> ></FONT> <BR><FONT SIZE=2>>> > Sorry... I thought most people knew this. Oracle says that if a query will</FONT> <BR><FONT SIZE=2>>> > return more than 20% of the rows of a table, it will use a full table </FONT> <BR><FONT SIZE=2>>> scan.</FONT> <BR><FONT SIZE=2>>> > So you DON'T tune it to use an index. In fact, as of 8i, I believe Oracle</FONT> <BR><FONT SIZE=2>>> > now recommends that if a query returns as little as 3-5% of a table, a </FONT> <BR><FONT SIZE=2>>> full</FONT> <BR><FONT SIZE=2>>> > table scan is the way to go.</FONT> <BR><FONT SIZE=2>>></FONT> <BR><FONT SIZE=2>>>A very valuable piece of information. How did I miss it!</FONT> <BR><FONT SIZE=2>>>Now I know what I am going to do on Monday. I had a feeling that</FONT> <BR><FONT SIZE=2>>>all those indeces are useless, now I know why they are.</FONT> <BR><FONT SIZE=2>>>Thank you very much.</FONT> <BR><FONT SIZE=2>>></FONT> <BR><FONT SIZE=2>>>Nicholas</FONT> <BR><FONT SIZE=2>>>--</FONT> <BR><FONT SIZE=2>>>Author: Nicholas Tufar</FONT> <BR><FONT SIZE=2>>> INET: ntufar_at_chemist.gen.tr</FONT> <BR><FONT SIZE=2>>></FONT> <BR><FONT SIZE=2>>>Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051</FONT> <BR><FONT SIZE=2>>>San Diego, California -- Public Internet access / Mailing Lists</FONT> <BR><FONT SIZE=2>>>--------------------------------------------------------------------</FONT> <BR><FONT SIZE=2>>>To REMOVE yourself from this mailing list, send an E-Mail message</FONT> <BR><FONT SIZE=2>>>to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in</FONT> <BR><FONT SIZE=2>>>the message BODY, include a line containing: UNSUB ORACLE-L</FONT> <BR><FONT SIZE=2>>>(or the name of mailing list you want to be removed from). You may</FONT> <BR><FONT SIZE=2>>>also send the HELP command for other information (like subscribing).</FONT> <BR><FONT SIZE=2>></FONT> <BR><FONT SIZE=2>>________________________________________________________________________</FONT> <BR><FONT SIZE=2>>Get Your Private, Free E-mail from MSN Hotmail at http://www.hotmail.com</FONT> <BR><FONT SIZE=2>></FONT> <BR><FONT SIZE=2>>--</FONT> <BR><FONT SIZE=2>>Author: Rachel Carmichael</FONT> <BR><FONT SIZE=2>> INET: carmichr_at_hotmail.com</FONT> <BR><FONT SIZE=2>></FONT> <BR><FONT SIZE=2>>Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051</FONT> <BR><FONT SIZE=2>>San Diego, California -- Public Internet access / Mailing Lists</FONT> <BR><FONT SIZE=2>>--------------------------------------------------------------------</FONT> <BR><FONT SIZE=2>>To REMOVE yourself from this mailing list, send an E-Mail message</FONT> <BR><FONT SIZE=2>>to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in</FONT> <BR><FONT SIZE=2>>the message BODY, include a line containing: UNSUB ORACLE-L</FONT> <BR><FONT SIZE=2>>(or the name of mailing list you want to be removed from). You may</FONT> <BR><FONT SIZE=2>>also send the HELP command for other information (like subscribing).</FONT> </P> <P><FONT SIZE=2>-- </FONT> <BR><FONT SIZE=2>Author: Regina Harter</FONT> <BR><FONT SIZE=2> INET: rharter_at_emc-inc.com</FONT> </P> <P><FONT SIZE=2>Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051</FONT> <BR><FONT SIZE=2>San Diego, California -- Public Internet access / Mailing Lists</FONT> <BR><FONT SIZE=2>--------------------------------------------------------------------</FONT> <BR><FONT SIZE=2>To REMOVE yourself from this mailing list, send an E-Mail message</FONT> <BR><FONT SIZE=2>to: ListGuru_at_fatcity.com (note EXACT spelling of 'ListGuru') and in</FONT> <BR><FONT SIZE=2>the message BODY, include a line containing: UNSUB ORACLE-L</FONT> <BR><FONT SIZE=2>(or the name of mailing list you want to be removed from). You may</FONT>Received on Mon Jun 12 2000 - 18:49:12 CDT
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