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Re: METALINK and OWS

From: Regina Harter <rharter_at_emc-inc.com>
Date: Mon, 12 Jun 2000 10:31:04 -0700
Message-Id: <10526.108716@fatcity.com>


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
>>
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>--
>Author: Rachel Carmichael
> INET: carmichr_at_hotmail.com
>
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Received on Mon Jun 12 2000 - 12:31:04 CDT

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