Re: Full scan vs index

From: Henry Poras <hrp_at_google.com>
Date: Thu, 10 Oct 2013 11:35:36 -0400
Message-ID: <CAAVg4uKDzs8v8zb+p3C76bJ2uUdA03=NwP5Ev-79US-AfKq_8Q_at_mail.gmail.com>

If you want to stick with index access, try adding 'lastname' to the PK index (index both columns).
Henry

On Thu, Oct 10, 2013 at 11:19 AM, Storey, Robert (DCSO) < RStorey_at_dcso.nashville.org> wrote:

> To follow up, Chris pointed out my error in my hint. Correctly formatted
> but wrong index.
> When I used the correct index in the hint, the index was used and the plan
> cost jumped from 1152 to 1840.
>
> Thanks all for the responses. Its been a learning morning
>
> From: David Ramírez Reyes [mailto:dramirezr_at_gmail.com]
> Sent: Thursday, October 10, 2013 9:11 AM
> To: Storey, Robert (DCSO)
> Cc: Uzzell, Stephan; Laimutis.Nedzinskas_at_seb.lt; Oracle L;
> oracle-l-bounce_at_freelists.org
> Subject: Re: Full scan vs index
>
> In some way yes, but more than the number of records on the table is the
> average of records on the results; the first query gives you as result the
> 14.5% (87,000 of 600,000) of the total records, which make the optimizer
> evaluate as a better option the Full Table scan; if the number of records
> were less (probably less than 5%), it may probably use Index instead of
> Full table scan.
>
> Just one more questions:
> Is the ordernum column defined (the PK) autoincrement -with a sequence and
> trigger, of course-?
>
>
> --
> http://www.freelists.org/webpage/oracle-l
>
>
>

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Received on Thu Oct 10 2013 - 17:35:36 CEST