Re: Function Based Index

From: Purav Chovatia <puravc_at_gmail.com>
Date: Thu, 20 Sep 2012 21:30:28 +0530
Message-ID: <CADrzpjG7qUR1U1VXxP=88u3D12qzUt-wY3r1U63=tKZ1cf8UgQ_at_mail.gmail.com>

Jonathan,
Can you pls help me understand how did you figure out the foll.: - that the row for table is much larger than the row estimate for the index - the cost of the table visits have been added to the cost of the range scan

Thanks.

On Fri, Sep 14, 2012 at 6:54 PM, Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk
> wrote:

>
> The fact that the row for the table is much larger than the row estimate
> for the index used to get to it suggests that you didn't collect stats on
> the hidden column underpinning the table when you created the index. The
> plan may have changed the following morning because of an overnight stats
> collection that rectified this mismatch. It's interesting, though that in
> this case the cost of the table visits have been added to the cost of the
> range scan - but perhaps that's a version thing.
>
> Regards
>
> Jonathan Lewis
> http://jonathanlewis.wordpress.com/all_postings
>
>

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Received on Thu Sep 20 2012 - 11:00:28 CDT