Re: need enhance feature for CBO :)
From: Ujang Jaenudin <ujang.jaenudin_at_gmail.com>
Date: Thu, 13 Nov 2008 15:11:54 +0700
Message-ID: <3edcb66e0811130011q51326348mb844136b64bbf75c@mail.gmail.com>
Date: Thu, 13 Nov 2008 15:11:54 +0700
Message-ID: <3edcb66e0811130011q51326348mb844136b64bbf75c@mail.gmail.com>
yes william,
that is what I mentioned on my 1st post. I think for the LIST partition oracle should do, but not sure for range and hash partitions....
-- thanks and regards ujang | oracle dba jakarta | http://ora62.wordpress.com On Thu, Nov 13, 2008 at 2:54 PM, William Robertson <william_at_williamrobertson.net> wrote:Received on Thu Nov 13 2008 - 02:11:54 CST
> I think Ujang's idea (correct me if I'm wrong) was that you could get the
> distinct key values from the partition definitions stored in the dictionary.
> However that information is not guaranteed to be accurate as you might have
> empty partitions, or you might have previously used ALTER TABLE EXCHANGE
> PARTITION WITHOUT VALIDATION.
>
>
> -----Original message-----
> From: Mark W. Farnham
> Date: 12/11/08 16:49
>
> Jared asks an interesting question, but I'm even more interested in why you
> think
>
>
>
> "I think scanning Primary key
> more efficient rather than roundtrip read PVC_U1 index and then again
> read PVC_PK index, due to IOT mapping..." ?
>
>
>
> Your query only needs the seq column. All the column seq values are in
> pvc_u1, which is smaller than the PK.
>
> So of course the CBO uses the smaller index. Since both SEQ and ES are in
> the PK, I can absolutely guarantee that pvc_u1 is smaller than the PK, which
> contains them and additional columns.
>
>
>
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