RE: A question about performance

Why is everyone jumping to conclusions about the data?

What is the distribution of the values in the table? How many rows per data block?
etc.

If there are > 10% ( or so ) with a value >= 0 then the index may be faster. If there are > 10% ( or so ) with a value <= 0 then the index may be slower.

e.g. a PK col + long col may only be 1 row per block that may screw you ideas up a bit. :-)

George

> -----Original Message-----
> From: "Singla, Sanjeev" <SSingla_at_oxhp.com> [mailto:SSingla_at_oxhp.com]
> Sent: Wednesday, June 21, 2000 3:30 PM
> To: SMTP_at_INL002@Servers["Multiple recipients of list ORACLE-L"
> <ORACLE-L_at_fatcity.com>]
> Subject: RE: A question about performance
>
>
> Full table scan will be faster.
> Reason: If it go for index scan it will get the rowids
> and come back
> with those
> rowids to scan the table because u are selecting all the
> columns so it has
> to do full
> scan of table also for getting everything.
> Index scan + full scan of table for actual data. (If going
> for index scan)
> ----------- Only table scan for actual blocks (Full scan)
>
> Cheers.
>
> -----Original Message-----
> Sent: Tuesday, June 20, 2000 11:35 PM
> To: Multiple recipients of list ORACLE-L
>
>
> Hi All:
> There is a question about performance.
> Table name : subscriber , primary key :
> subscr_id , with
> over 5000000 records .
>
> CASE 1 : select *
> from subscriber ;
> (FULL TABLE SCAN)
>
> CASE 2 : select *
> from subscriber
> where subscr_id > 0 ;
> (USE INDEX)
>
> Could anyone tell me which ones performance is
> better , or
> they are the same ??
>
> Thank you in advance.
>
>
> Tiffany
> E-mail tiffanydu_at_pcdc.com.tw
>
>
> --
> Author: =?big5?B?VGlmZmFueSBEdSAoIKf5p0qq4iAp?=
> INET: TiffanyDu_at_pcdc.com.tw
>
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> Author: Singla, Sanjeev
> INET: SSingla_at_oxhp.com
>
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Received on Wed Jun 21 2000 - 09:31:20 CDT