Re: Sudden plan change related to "VIEW PUSHED PREDICATE" with cost difference of 1M VS 13G

As we dont really want to run the MERGE/DML query on production. And also the MERGE query is not able to finish with the new path , So is it okay to just do like below explain plan to get the 10053 trace? Hoping that the MERGE query will not be executed behind the scene but just the plan will be generated. Please correct me if wrong here.

alter session set tracefile_identifier='mergequeryplan';

alter session set events='10053 trace name context forever, level 1';

Explain plan for MERGE INTO HIST.....;

alter session set events='10053 trace name context off';

_at_Mohamed, Regarding the nested loop and hash join which is happening towards the end of the plan, yes both of the sql monitor which i posted for "post patch" are running slow.

_at_Andy , Regarding the "nested loop outer" while MERGE INTO i.e at the top of the plan, If i see the before patch plan which was running fast, in that this was NESTED LOOP OUTER only. But yes as you said , i will try to force if at all i will be able to make that 'HASH JOIN OUTER' any way.

On Thu, 12 May 2022, 3:15 pm Mohamed Houri, <mohamed.houri_at_gmail.com> wrote:

> Pap
>
> You have shown two SQL monitors for the new plan one using a NESTED LOOP
> and one using HASH JOIN both *without *VIEW PUSHED PREDICATE. Are both
> plans bad for you? If not, then bear in mind that it is normal to not have
> a VIEW PUSHED PREDICATE in the presence of a HASH JOIN. This transformation
> is governed by NESTED LOOPS only.
>
> Therefore, if the case of the NESTED LOOPS poses a problem, you can get
> the 10053 trace file to see why the VIEW PUSHED PREDICATE has not been
> selected by Oracle.
>
> Best regards
> Mohamed
>
> Le jeu. 12 mai 2022 à 11:08, Noveljic Nenad <nenad.noveljic_at_vontobel.com>
> a écrit :
>
>> Hi Pap,
>>
>>
>>
>> The optimizer trace (event 10053) should reveal the reason for discarded
>> JPPD.
>>
>>
>>
>> Best regards,
>>
>>
>>
>> Nenad
>>
>>
>>
>> *From:* oracle-l-bounce_at_freelists.org <oracle-l-bounce_at_freelists.org> *On
>> Behalf Of *Andy Sayer
>> *Sent:* Donnerstag, 12. Mai 2022 08:32
>> *To:* Pap <oracle.developer35_at_gmail.com>
>> *Cc:* Oracle L <oracle-l_at_freelists.org>
>> *Subject:* Re: Sudden plan change related to "VIEW PUSHED PREDICATE"
>> with cost difference of 1M VS 13G
>>
>>
>>
>> **** E-Mail from outside Vontobel:* Do not click on links or open
>> attachments unless you know the content is safe. ***
>>
>> Hi Pap,
>>
>>
>>
>> That monitor is still dong a nested loop for the merge into HIST, we can
>> see it’s managed it 226 times already. I want to see what happens when it
>> hash joins to HIST so it only has to do that big group by + table scan once
>> and the other access as a one off table scan.
>>
>>
>>
>> Have a play with pathfinder, it might not find anything but if it does,
>> still the bug no into MOS and see what’s relevant. It might be something
>> safe, it might be something that’s saving you from corruption. If Oracle
>> has turned off predicate push down in a merge condition because of a
>> corruption bug and doesn’t have a work around then you are just going to
>> have to try my alternatives.
>>
>>
>>
>> Thanks,
>>
>> Andy
>>
>>
>>
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> Houri Mohamed
>
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