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.
On Sat, Apr 14, 2018 at 5:19 PM, Frits Hoogland <frits.hoogland@xxxxxxxxx>
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.
Mobile: +31 6 14180860
On 10 Apr 2018, at 18:13, Ls Cheng <exriscer@xxxxxxxxx> wrote:
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?