Re: USE_CONCAT plan operation after April 2021 Bundle Patch (12.1.0.2) Questions

As far as copying the OUTLINE portion, yep have definitely done that .

Taking the OUTLINE from the original profile and putting it in the test sql runs really, really badly.

Unfortunately I don't have any unpatched version of the db as we patch all our non-prod envs before moving to Prod :/

I've been throwing *everything *at this query to try to get the runtime back down (session params, hints of all sorts). It refuses to comply :)

This query uses some odd structure for WITH statements inside subqueries that is quite maddening to try to decipher/work through.

Also of note all of those adaptive params are ones we disabled by turning off the adaptive features functionality in 12.1 when we went to Exadata working with Oracle's Real World Performance tuning team as this db is a real pain.

Chris

On Fri, Aug 27, 2021 at 10:12 AM Jonathan Lewis <jlewisoracle_at_gmail.com> wrote:

> Is the plan showing the operation CONCATENATION, or OR_EXPANSION as its
> implementation of USE_CONCAT() ?
>
> The thing I notice as significant (apart from the use_concat, of course)
> is the
> OPT_PARAM('_optimizer_null_accepting_semijoin' 'false')
> which may be why the end up with a lateral view
> "VW_LAT_EA451CA1"_at_"SEL$EA451CA1"
> The other opt_params look as if they relate to the splitting of the 12.1
> adaptive optimization parameter into two parts (and that could be part of
> the problem, of course).
>
> Have you tried cutting and pasting the Outline from the good plan into the
> SQL to see if the hints are sufficient to reproduce the plan?
> Can you run the query on a patched as well as unpatched version of the
> software? If so running with the CBO trace (10053) enabled would allow you
> to compare all the optimizer parameters and fix_controls that vary between
> the two instances. Search for the heading PARAMETERS USED BY THE OPTIMIZER
>
> Regards
> Jonathan Lewis
>
>
>
>
>
>
>
>
>
> On Fri, 27 Aug 2021 at 14:50, Chris Taylor <
> christopherdtaylor1994_at_gmail.com> wrote:
>
>> For this it was "_no_or_expansion" to test getting rid of the
>> USE_CONCAT. (H/T to Noveljic for the help finding the param)
>>
>> It didn't make any difference however.
>>
>> Thanks,
>> Chris
>>
>>
>> On Fri, Aug 27, 2021 at 9:11 AM Noveljic Nenad <
>> nenad.noveljic_at_vontobel.com> wrote:
>>
>>> Hi,
>>>
>>>
>>>
>>> Could you try
>>>
>>>
>>>
>>> ALTER SESSION SET "_optimizer_cbqt_or_expansion"=off;
>>>
>>>
>>>
>>> Best regards,
>>>
>>>
>>>
>>> Nenad
>>>
>>>
>>>
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