Re: Priority of profile baseline patch

Thank You So much for the clarification. It really helped me understand the flow.

*"with enabled=yes but accepted=NO and*

*1) All the accepted and enabled SQL plan baselines will be reproduced and costed. The best costed and reproduced plan will be used*

*2) If none of the accepted and enabled SQL plan baselines is reproducible then the CBO plan added to the SQL plan baseline list with enabled=yes but accepted=NO will be used"*

Related to the above point ,I am wondering about the fact that , for the first time, when the sql plan baseline was created , it must have been created on top of one of the available awr plans or cursor cache plans, which the query must have taken in the past execution. So in what situation that same plan won't get reproducible, such that the optimizer has to go for a non accepted plan i.e the second option above which can be riskier one?

Actually it's matching to one situation, we had encountered a scenario in the past in which we had hints used in a query and on top of that, that sql was having a profile created using the outline of a awr plan. And again it was somehow going for a bad execution path so someone created a baseline on another path from the available awr plan. And this caused the optimizer to go for a different plan altogether, breaking one of the functionality. So wanted to understand in what situation the existing baseline accepted+enabled plan can be non reproducible?

On Fri, Dec 17, 2021 at 8:31 PM Mohamed Houri <mohamed.houri_at_gmail.com> wrote:

> Pap,
>
> *As you mentioned above and also from the diagram, it's only when the plan
> evaluated using either SQL patch/stored outline/SQL profile/hints, etc
> matches one of the sql_handle with accepted=YES and enabled=YES, then that
> plan will be in use. *
>
> Correct.
>
> *But in case none of the accepted=yes and enabled=yes SQL plan baseline
> matches with the incoming parsed plan which is generated using SQL
> patch/hints/SQL profile, then that new plan will be added to the SQL plan
> baseline list with enabled=yes but accepted=NO and will be in use*
>
> It’s not exactly correct
>
> If the incoming parsed plan which is generated using SQL patch/hints/SQL
> profile does not match one of the accepted=yes and enabled=yes SQL plan
> baselines, then that new plan will be added to the SQL plan baseline list
> with enabled=yes but accepted=NO and
>
> 1) All the accepted and enabled SQL plan baselines will be reproduced
> and costed. The best costed and reproduced plan will be used
>
> 2) If none of the accepted and enabled SQL plan baselines is
> *reproducible* then the CBO plan added to the SQL plan baseline list with
> enabled=yes but accepted=NO will be used
>
> *My thought initially was, if the incoming parsed plan(which has came
> through the profile/patch/hints etc..) doesn't match with any of the
> baselines( accepted=yes and enabled=yes) baselines then, it should go back
> and use one of the baselines( accepted=yes and enabled=yes) having lower
> cost only. *
>
> Correct provided the SPM baseline plans are reproducible
>
> Best regards
>
> Mohamed
>
> Le ven. 17 déc. 2021 à 15:57, Lok P <loknath.73_at_gmail.com> a écrit :
>
>> Trying to interpret the diagram in Mohamed's blog it looks like a two
>> step process 1) It will try to use your hints/sql profile/patches etc to
>> come up with a plan and then the plan must match with one of the plans in
>> the sql plan baseline having accepted=yes and enabled=yes. but in case it
>> doesn't match then it will use its own mind(i.e. optimizer default setups
>> without considering those hints/profile/patches) and come up with a
>> different plan altogether which will be in use even A*ccepted='NO'* for
>> this new plan in the sql plan baseline list. And this is where things can
>> get screwed up , if someone creates a sql profile/sql patch thinking that
>> their plan is going to be used :). .In short sql profile/patches/hints can
>> totally be ignored and give you surprises if you create baselines for that
>> sql. So, does that mean there is no guarantee that the plan which we have
>> set through the sql plan baseline will be used 100% of the time.?
>>
>>
>> On Fri, Dec 17, 2021 at 8:06 PM Pap <oracle.developer35_at_gmail.com> wrote:
>>
>>> Thank you so much Mohamed.
>>>
>>> *"When generating this execution plan, all things being equal, Oracle
>>> will use the set of hints contained in the SQL Profile or the SQL patch. It
>>> is only when the execution plan has been generated that the SPM finally
>>> comes into play."*
>>>
>>> As you mentioned above and aso from the diagram , it's only when the
>>> plan evaluated using either sql patch/stored outline/sqlprofile/hints etc
>>> matches one of the sql_handle with accepted=YES and enabled=YES, then that
>>> plan will be in use. But in case none of the accepted=yes and enabled=yes
>>> sql plan baseline matches with the incoming parsed plan which is
>>> generated using sql patch/hints/sql profile, then that new plan will be
>>> added to the sql plan baseline list with enabled=yes but accepted=NO, and
>>> will be in use. And in this case isn't it incorrect for Oracle to use a
>>> plan which has not been accepted by us in the sql plan baseline? Am I
>>> missing anything here?And if this is true , then there is no guarantee that
>>> the enabled and accepted baselines are always going to be the only plans to
>>> be in use by the sql optimizer.
>>>
>>> My thought initially was , if the incoming parsed plan(which has came
>>> through the profile/patch/hints etc..) doesn't match with any of the
>>> baselines( accepted=yes and enabled=yes) baselines then , it should go back
>>> and use one of the baselines( accepted=yes and enabled=yes) having lower
>>> cost only.
>>>
>>>
>>>
>>> On Fri, Dec 17, 2021 at 3:17 PM Mohamed Houri <mohamed.houri_at_gmail.com>
>>> wrote:
>>>
>>>> Hello
>>>>
>>>> *In other words the sql profile or sql patch helps to create new
>>>> plans based on the embedded hints however presence of baseline with
>>>> accepted +enabled flag as 'YES' is always going to rule at the end. Correct
>>>> if my understanding is wrong here?*
>>>>
>>>> The underlined part is incorrect
>>>>
>>>> If you look at the picture I designed in this article
>>>>
>>>>
>>>> https://hourim.wordpress.com/2015/10/01/oracle-optimizer-and-spm-plan-interaction/
>>>>
>>>> You will realize that the presence of an SPM has *no influence on the
>>>> ordinary work of the CBO*. Initially, Oracle will produce its
>>>> execution plan ignoring the presence or absence of an SPM.
>>>>
>>>> When generating this execution plan, all things being equal, Oracle
>>>> will use the set of hints contained in the SQL Profile or the SQL patch.
>>>> *It is only when the execution plan has been generated that the SPM
>>>> finally comes into play.*
>>>>
>>>> And what exactly will this SPM do?
>>>>
>>>> It will simply ensure that only the execution plan contained in the SPM
>>>> baseline will be used regardless of how this plan has been generated, via
>>>> SQL Profile, via SQL patch, or without any of those two features.
>>>>
>>>> Of course, this insurance against a bad surprise(a non-desired
>>>> execution plan) is only possible if the plan in the SPM is reproducible at
>>>> the time of the execution of the request.
>>>>
>>>> Hope this is clear
>>>>
>>>> Best regards
>>>>
>>>> Mohamed Houri
>>>>
>>>>
>>>>
>>>> Le ven. 17 déc. 2021 à 05:18, Pap <oracle.developer35_at_gmail.com> a
>>>> écrit :
>>>>
>>>>> Thank you so much Andy.
>>>>>
>>>>> If I get it correct, it's the sql profile(which is generally a
>>>>> combination of opt_estimate hints) which oracle will use to evaluate the
>>>>> plans but it's ultimately the sqlplan baselines (which must be in
>>>>> accepted+enabled) state which is going to be used finally.
>>>>>
>>>>> And in scenarios where we use technique to manually create sql profile
>>>>> by passing exact outline hints (but not with opt_etsimate hints) i.e. using
>>>>> procedure dbms_sqltune.import_sql_profile where we have ability to
>>>>> pass the exact full query outline hints which restricts the execution path
>>>>> to one. In those cases it will mostly fix the exact one execution path for
>>>>> the query no matter how many times it parses. And in the presence of such a
>>>>> sql profile , if the sql plan baseline has exactly the same path
>>>>> enabled+accepted that is going to be used or else it's going to be
>>>>> completely discarded and the priority will be given to the baseline which
>>>>> is in accepted+enabled state. (And the discarded plan i.e the parsed plan
>>>>> using sql profile may be added a new baseline to the list with accepted
>>>>> flag as NO). Which means sql plan baseline having enabled+accepted flag
>>>>> as "YES" will take the precedence always irrespective of sql profile/sq
>>>>> patch etc. Is this understanding correct?
>>>>> Or
>>>>> In other words the sql profile or sql patch helps to create new plans
>>>>> based on the embedded hints however presence of baseline with
>>>>> accepted +enabled flag as 'YES' is always going to rule at the end. Correct
>>>>> if my understanding is wrong here?
>>>>>
>>>>> On Fri, Dec 17, 2021 at 1:53 AM Andy Klock <andy_at_klockmail.com> wrote:
>>>>>
>>>>>> Hi Laurentiu,
>>>>>>
>>>>>> ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
>>>>>> On Thursday, December 16th, 2021 at 3:08 PM, Pap <
>>>>>> oracle.developer35_at_gmail.com> wrote:
>>>>>>
>>>>>> So in cases where the SQL profile or SQL patch has some hints (say
>>>>>> FTS on tab1) which is exactly opposite than that of the one in SQL plan
>>>>>> baseline(say index access for tab1). In that scenario will oracle follow
>>>>>> profile/patch or the baseline path?
>>>>>>
>>>>>>
>>>>>> If a cursor has "accepted" baselines, then that is typically what the
>>>>>> CBO is going to prefer. When there are multiple accepted plans, then the
>>>>>> CBO will pick the plan with the lowest cost. For cursors that also have a
>>>>>> SQL Profile, then those hints and opt_estimates are applied which may
>>>>>> affect the cost of the baseline plans that the CBO will pick.
>>>>>>
>>>>>> Maria wrote a nice article about it [1] in 2012 which I think is
>>>>>> still relevant, but often when you have cursors with lots of baselines, SQL
>>>>>> Profiles, and patches it's time to fix the stats or change the code :)
>>>>>>
>>>>>> Andy K
>>>>>>
>>>>>> [1]
>>>>>> https://blogs.oracle.com/optimizer/post/what-is-the-difference-between-sql-profiles-and-sql-plan-baselines
>>>>>>
>>>>>
>>>>
>>>> --
>>>>
>>>> Houri Mohamed
>>>>
>>>> Oracle DBA-Developer-Performance & Tuning
>>>>
>>>> Visit My - Blog <http://www.hourim.wordpress.com/>
>>>>
>>>> Let's Connect - <http://fr.linkedin.com/pub/mohamed-houri/11/329/857/>*Linkedin
>>>> Profile <http://fr.linkedin.com/pub/mohamed-houri/11/329/857/>*
>>>>
>>>> My Twitter <https://twitter.com/MohamedHouri> - MohamedHouri
>>>> <https://twitter.com/MohamedHouri>
>>>>
>>>>
>
> --
>
> Houri Mohamed
>
> Oracle DBA-Developer-Performance & Tuning
>
> Visit My - Blog <http://www.hourim.wordpress.com/>
>
> Let's Connect - <http://fr.linkedin.com/pub/mohamed-houri/11/329/857/>*Linkedin
> Profile <http://fr.linkedin.com/pub/mohamed-houri/11/329/857/>*
>
> My Twitter <https://twitter.com/MohamedHouri> - MohamedHouri
> <https://twitter.com/MohamedHouri>
>
>

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