Well, there are several more changes you didn't mention: new type of
histograms, much larger histograms and a new way to calculate clustering
factor.
On 05/01/2017 02:29 AM, Stefan Koehler wrote:
Hey Mladen,
The optimizer in 12.1 is almost completely rewritten, there are bound to bePlease tell us more about that. I know that Oracle has completely re-engineered
some bugs.
/ re-written some transformations like star-transformation in the past
but that Oracle has re-written most of the optimizer in 12.1 is new (quite
apart from the fact that nothing would justify the time and costs of this).
Thank you.
P.S.: If you mean all of the adaptive features - most of it is happening in the
run-time engine code (e.g. statistics collector, etc.) and not in the
optimizer code (e.g. inflection point). Dynamic Sampling (in case of SPDs / ADS) is
nothing really new - just a "tiny" extension to the existing DS
code.
Best Regards
Stefan Koehler
Independent Oracle performance consultant and researcher
Website: http://www.soocs.de
Twitter: @OracleSK
Upcoming online seminar: http://tinyurl.com/17-06-13-Shared-Pool-Internals
Mladen Gogala <gogala.mladen@xxxxxxxxx> hat am 30. April 2017 um 19:04
geschrieben:
On 04/30/2017 12:42 PM, Thomas Roach wrote:
> > If it's 12.1, then if you are going to set any parameter outside
of defaults, it would be optimizer_features_enable back to 11.2.0.4.
> > That's usually when people throw in the towel if they can't figure it
out otherwise.
> That will not do much for you. OFE will set up some constants to their
11.2.0.4 values, but the optimizer code will still be the code from
> version 12. There are no shortcuts. My usual advice to the customers is to
wait for the first major patch set of the version 12.2 to upgrade
> and not to upgrade to 12.1. The optimizer in 12.1 is almost completely
rewritten, there are bound to be some bugs. Those bugs usually get
> polished in the second edition. That was the case with 11.1, although
11.2.0.2 was almost unusable. Somebody on this group has even recently
> called 11.2.0.3 a "buggy cesspool". The new versions are so complex and
have so many interacting features that it has become extremely hard to
> write something that will not be buggy.
