Re: Anyone know any WP which explains about FTS vs Index Scan?

Hi

He sticked with late 90's theory however he actually pointed me some oracle 11.2 documentation links which talks about reduce I/O, use index when possible, then I started searching some stuff from Oracle and I cannot find a lot which says index scan is not always the best (I found the explanation in asktom only). So I question if Oracle documentation is actually promoting index scans! :-)

I also looked for why FTS is preferable in DWH where massive data need sto be accessed without much luck neither.

I gave him examples, I explained why CBO is introduced to make decision when FTS is better etc and I think he started to believe me but because of his ego he does not want to stop discuss.

Thanks

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On Sat, Apr 14, 2018 at 5:19 PM, Frits Hoogland <frits.hoogland_at_gmail.com> wrote:

> My question would be: why an index range scan MUST be used? What is the
> reason for this person to deem it mandatory?
>
> This would also discard unique index access, which is a different access
> path than an index range scan.
>
> I question the knowledge of the person if he/she can not see the point of
> a full table scan or any other different access path.
> Even if the documentation would state that an index must be used, and does
> not provide a valid reason for why it shouldn’t be used, I would discard
> the advise in the documentation. There are lots of examples where the
> official documentation is incorrect, and even experts might be wrong; for
> something to be written in a book doesn’t make it the truth.
>
>
> Frits Hoogland
>
> http://fritshoogland.wordpress.com
> frits.hoogland_at_gmail.com
> Mobile: +31 6 14180860
>
> On 10 Apr 2018, at 18:13, Ls Cheng <exriscer_at_gmail.com> wrote:
>
> Hi
>
> I have a Dinosaur stating we must always use index range scan no matter
> OLTP or DWH systems. This guys still lives in the late 90's and Oracle 7
> (although he claims he is 18 years veteran expert from 7 up to 12c), the
> thing is I cannot find any Oracle WP or similar in the docs which states
> Full Table Scan is not evil except Tom Kyte (asktom). I have even demo-ed
> him with a very simple two table join example with FTS and index range
> effect when a large amount of data need to be accessed, still he says in
> Oracle docs states that scattered reads (FTS) mist be reduced!
>
> Does anyone know any official pointer, in WP form or MOS support note
> which talks about FTS vs index scans?
>
> Cheers
>
>
>
>

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