Re: high temp space usage for same analytic function on latest version

Since I've noticed Bloom filters as an anomaly, it might be worth checking if you're patched for:
"Bug 30618406 - Huge PGA memory consumption by bloom filters (qesblfilter_seg) in px slaves in full partition-wise join"

I know this plan isn't using full PW joins - but (read the details) - your parallel operation uses a lot of memory, and then a lot of temp space. Sometimes the bug goes a lot further than the initial description.

Marked as fixed in 23.1, but I can see patches for 19.16 in the RU.

Regards
Jonathan Lewis

On Tue, 15 Nov 2022 at 07:15, Jonathan Lewis <jlewisoracle_at_gmail.com> wrote:

>
> I've taken a few minutes to look through the github material. The headings
> don't agree with the contents. Here's a list showing each heading plus two
> lines from the Outline Data under the heading:
>
> Display cursor plan from version 11.2.0.4
> OPTIMIZER_FEATURES_ENABLE('19.1.0')
> DB_VERSION('19.1.0')
>
>
> Execution which is failing in 19.15 version with high tempspace consumption
> OPTIMIZER_FEATURES_ENABLE('11.2.0.4')
> DB_VERSION('19.1.0')
>
>
> Execution which was running fine in 19.11 version
> OPTIMIZER_FEATURES_ENABLE('11.2.0.4')
> DB_VERSION('11.2.0.4')
>
>
> There doesn't seem to be any point in spending time looking at detail when
> I've got no confidence that the bits of information supplied belong
> together.
>
>
> A couple of high visibility points, though:
> a) the version labelled "Execution which was running fine in 19.11
> version" reported OPT_PARAM('optimizer_dynamic_sampling' 3) in its outline
> data, and that could have helped Oracle get better estimates on some of the
> predicates that included functions of columns.
> b) the version labelled "Display cursor plan from version 11.2.0.4"
> included Bloom Filtering sent to storage on the massive tablescan where I
> pointed out the massive CPU anomaly in an earlier post.
> 76 - storage((COALESCE("FPT"."DEL_FLG",'N')='N' AND
> TRUNC(INTERNAL_FUNCTION("FPT"."H_DT_TIM"))=:B1 AND
> SYS_OP_BLOOM_FILTER(:BF0000,"FPT"."A_FK")))
> filter((COALESCE("FPT"."DEL_FLG",'N')='N' AND
> TRUNC(INTERNAL_FUNCTION("FPT"."H_DT_TIM"))=:B1 AND
> SYS_OP_BLOOM_FILTER(:BF0000,"FPT"."A_FK")))
>
>
> Regards
> Jonathan Lewis
>
>
>
> On Mon, 14 Nov 2022 at 17:18, yudhi s <learnerdatabase99_at_gmail.com> wrote:
>
>> Thank You Sayan and Jonathan.
>>
>> As you suggested, as a quick thing , in the select query, I was trying
>> this hint in the main block to influence optimizer to increase the
>> resulting rows ~18 times from the CTE "C" , but its not getting reflected
>> in the plan, which means optimizer is not considering this, but then it
>> should appear in the hint report section of the plan as error or unused
>> etc.. but it is not getting published there too, so not sure why is this
>> happening. Is there anything wrong in the hint below which i am using?
>>
>> I am using below hint in the main select query which performs outer join
>> with the "cte" Table C
>>
>> /*+OPT_ESTIMATE( TABLE, C, scale_rows=18)*/
>>
>> Also , I tried as below but seeing no change to the tempspace consumption
>> though.
>>
>> cast(RPAD (SUBSTR (CP.CP_NBR, 1, CP.CPCL_NBR - X.RN),CASE
>> CP.PANL_CNT WHEN 0 THEN 16 ELSE CP.PANL_CNT END, '9') as
>> varchar2(22)) AS HIGH_VALUE
>>
>> cast(RPAD (SUBSTR (CP.CP_NBR, 1, CP.CPCL_NBR - X.RN), CASE
>> CP.PANL_CNT WHEN 0 THEN 16 ELSE CP.PANL_CNT END, '0') as varchar2(22)
>> ) AS LOW_VALUE,
>>
>>
>>
>>
>> On Mon, 14 Nov, 2022, 4:22 pm Jonathan Lewis, <jlewisoracle_at_gmail.com>
>> wrote:
>>
>>> Still avoiding spending a lot of time on the github text.
>>>
>>> a) You materialize a CTE that invovles a connect by query that
>>> generates 18 rows - use the opt_estimate() hint to tell Oracle that the
>>> materialized view holds 18 times the rows it expects. (If you examine the
>>> plan the optimizer allows for ONE row coming from dual, not 18).
>>>
>>> b) You have several places where you use expresssions like
>>> substr(c_nbr,1,4) in predicates . Create (optionally invisible) virtual
>>> columns for these expressions and gather stats on them, this will give the
>>> optimizer a better chance of getting the right arithmetic, especially for
>>> cases where the expression needs a frequency (or top-frequency) histogram.
>>> Invisible is safest for existing production code, but you may need to test
>>> carefully to see if the optimizer manages to use the stats from the virtual
>>> columns when it sees the equivalent expressions.
>>>
>>> Regards
>>> Jonathan Lewis
>>>
>>>
>>>
>>>
>>> On Sun, 13 Nov 2022 at 14:28, yudhi s <learnerdatabase99_at_gmail.com>
>>> wrote:
>>>
>>>> Thank you Lok. Actually the join is not exactly on the columns but with
>>>> some functions so that might be the case why it seems like Cartesian.
>>>>
>>>> However the point is , this query has not been changed and I agree that
>>>> it may be because the data has been increased a lil in one of the table 'C'
>>>> or 'T' , so the join output has been increased from 7billion to 10billion
>>>> but how come that justifies the temp space requirement from 20gb to
>>>> 2.5terabyte it not twice or thrice but multiple times.
>>>>
>>>> As this query is running in parallel-16 degree because of a underlying
>>>> table degree , and considering no other option at hand, so I was thinking
>>>> if by increasing or decreasing the parallelism with help of hints will help
>>>> in completing the query at least with lesser temp space(we have 2.5TB of
>>>> temp space with us right now currently) ? Or any other possible option to
>>>> make this query succeed?
>>>>
>>>> Just to note , we had initially 200gb of temp space but just with the
>>>> hope that this query may finish, we already increased it to 2.5TB now, but
>>>> still no luck and the query is failing and it's happening after this 19.15
>>>> patch.
>>>>
>>>>
>>>> On Sun, 13 Nov, 2022, 6:06 pm Lok P, <loknath.73_at_gmail.com> wrote:
>>>>
>>>>> The below section you posted shows the input to 'Hash join outer' were
>>>>> ~1Million and 37milion respectively, but the result came from the outer
>>>>> join is ~7billion. So is there any oddity in the data in table 'T' and 'C'
>>>>> which is playing a role which is increasing the rows input to your
>>>>> analytical function recently?
>>>>>
>>>>>
>>>>> SQL Plan Monitoring Details (Plan Hash Value=2056239125)
>>>>>
>>>>> =================================================================================================================================================================================================================================================================================
>>>>> | Id | Operation
>>>>> | Name | Rows | Cost | Time | Start |
>>>>> Execs | Rows | Read | Read | Write | Write | Cell | Mem | Temp
>>>>> | Activity | Activity Detail |
>>>>> | |
>>>>> | | (Estim) | | Active(s) | Active |
>>>>> | (Actual) | Reqs | Bytes | Reqs | Bytes | Offload | (Max) | (Max)
>>>>> | (%) | (# samples) |
>>>>>
>>>>> =================================================================================================================================================================================================================================================================================
>>>>> |
>>>>> | | | | | |
>>>>> | | | | | | | |
>>>>> | | direct path read temp (553) |
>>>>> | |
>>>>> | | | | | |
>>>>> | | | | | | | |
>>>>> | | direct path write temp (47) |
>>>>> | 31 | HASH JOIN RIGHT OUTER
>>>>> | | 9M | 2M | 1676 | +218 |
>>>>> 16 | 7G | | | | | | 217M |
>>>>> | 23.08 | Cpu (4041) |
>>>>> | 32 | BUFFER SORT
>>>>> | | | | 4 | +216 |
>>>>> 16 | 1M | | | | | | 97M |
>>>>> | | |
>>>>> | 33 | PX RECEIVE
>>>>> | | 10647 | 24 | 4 | +216 |
>>>>> 16 | 1M | | | | | | |
>>>>> | | |
>>>>> | 34 | PX SEND HASH
>>>>> | :TQ10005 | 10647 | 24 | 1633 | +216 |
>>>>> 1 | 1M | | | | | | |
>>>>> | 0.01 | Cpu (2) |
>>>>> | 35 | VIEW
>>>>> | | 10647 | 24 | 1632 | +217 |
>>>>> 1 | 1M | | | | | | |
>>>>> | | |
>>>>> | 36 | TABLE ACCESS STORAGE FULL
>>>>> | SYS_TEMP_0FDA1E71E_D71F1BDE | 10647 | 24 | 1632 | +217 |
>>>>> 1 | 1M | 106 | 104MB | | | | |
>>>>> | 0.01 | cell multiblock physical read (1) |
>>>>> | 37 | PX RECEIVE
>>>>> | | 9M | 2M | 1676 | +218 |
>>>>> 16 | 37M | | | | | | |
>>>>> | 0.05 | Cpu (9) |
>>>>> | 38 | PX SEND HASH
>>>>> | :TQ10009 | 9M | 2M | 1677 | +217 |
>>>>> 16 | 37M | | | | | | |
>>>>> | 0.13 | Cpu (23) |
>>>>> | 39 | VIEW
>>>>> | | 9M | 2M | 1677 | +217 |
>>>>> 16 | 37M | | | | | | |
>>>>> | | |
>>>>>
>>>>> On Sun, Nov 13, 2022 at 2:34 AM yudhi s <learnerdatabase99_at_gmail.com>
>>>>> wrote:
>>>>>
>>>>>> Thank you Jonathan.
>>>>>> Actually the original query was a long one so i was trying to reduce
>>>>>> the complexity by just posting the particular section of the query which
>>>>>> was causing the temp space spike. But I agree that just a partial query
>>>>>> doesn't make much sense. Also my apology as the plan format was distorted.
>>>>>>
>>>>>> I have again posted the exact query below with the actual object
>>>>>> names being replaced with dummy names. I have posted the plan in the github
>>>>>> in the link below, so the sql execution plan format will be intact. And I
>>>>>> am not having the "display cursor" plan for the current runs/failures for
>>>>>> this INSERT query, so i have posted the sql monitors for them and i had the
>>>>>> display cursor plan when it was running fine in 11.2.0.4 so i posted that
>>>>>> just for reference. Also I have copied and pasted the outline section from
>>>>>> the display_awr below each of the sqlmonitor plan.
>>>>>>
>>>>>>
>>>>>> https://gist.github.com/databasetech0073/714263bce477f624763f757e457cb861
>>>>>>
>>>>>> As mentioned earlier, the section of the plan which is doing the
>>>>>> outer join is below and it results in ~10billion rows. Which then is passed
>>>>>> to the analytical function. Was trying to understand, Is there any possible
>>>>>> way to minimize the temp space consumption in this scenario? because we
>>>>>> kept on increasing the temp space assuming it would succeed somehow, but
>>>>>> it just kept consuming 2.5TB+ space and then also it failed with "Ora-01652
>>>>>> unable to extend temp segment .." as it saturates all allocated temp
>>>>>> space?
>>>>>> As far as I know the encryption/TDE was already there in this
>>>>>> database before we moved from 19.11 to 19.15. I will double check with the
>>>>>> infra team on this.
>>>>>>
>>>>>> "LEFT OUTER JOIN C
>>>>>> ON SUBSTR (T.C_NBR, 1, 4) = C.BNK_ID_NB_4
>>>>>> AND LENGTH (T.C_NBR) = C.PANL_CNT
>>>>>> AND T.C_NBR BETWEEN C.LOW_VALUE AND C.HIGH_VALUE) S"
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> On Sat, Nov 12, 2022 at 12:50 PM Jonathan Lewis <
>>>>>> jlewisoracle_at_gmail.com> wrote:
>>>>>>
>>>>>>> >> We reran the query and it took a different plan hash value ,
>>>>>>> however the path is almost similar wrt the line which does "Outer join" and
>>>>>>> the "analytical function" evaluation. I have posted the specific section of
>>>>>>> sql monitor below with predicate and column projection for that run.
>>>>>>>
>>>>>>> The supplied outputs are virtually unreadable, for different
>>>>>>> execution plans, for different versions (and youve changed from 19.11 for
>>>>>>> the "slow" query to 11.2.0.4!) , and partial. I'm not going to look at them.
>>>>>>>
>>>>>>> >> However, the sql monitor shows status as 'error' out after
>>>>>>> sometime(~30minutes)) but the underlying sessions(~33 parallel sessions)
>>>>>>> kept on running for 2hrs+
>>>>>>>
>>>>>>> That looks like the behaviour that Mohamed Houri has written about
>>>>>>> in the past:
>>>>>>> https://hourim.wordpress.com/2020/03/07/sql-monitor-flaw/
>>>>>>>
>>>>>>> I'd forgotten it would be harder to collect the correct statistics
>>>>>>> from all the processes when running a parallel query - finding sessions by
>>>>>>> SQL_ID could work, but using views like v$px_sesstat etc. is safer.
>>>>>>> Nothing stands out from the information you supplied about wait events, and
>>>>>>> the only "unusual" thing in the session activity is that you are writing
>>>>>>> encrypted blocks to the temporary tablespace - were you doing that in the
>>>>>>> earlier version? It shouldn't explain a massive increase in space
>>>>>>> requirements, but it might be relevant - it would help to explain an
>>>>>>> increase in CPU.
>>>>>>>
>>>>>>>
>>>>>>> Regards
>>>>>>> Jonathan Lewis
>>>>>>>
>>>>>>>
>>>>>>> On Fri, 11 Nov 2022 at 17:07, yudhi s <learnerdatabase99_at_gmail.com>
>>>>>>> wrote:
>>>>>>>
>>>>>>>> Thank You Sayan, Jonathan.
>>>>>>>>
>>>>>>>> We reran the query and it took a different plan hash value ,
>>>>>>>> however the path is almost similar wrt the line which does "Outer join" and
>>>>>>>> the "analytical function" evaluation. I have posted the specific section of
>>>>>>>> sql monitor below with predicate and column projection for that run.
>>>>>>>> However, the sql monitor shows status as 'error' out after
>>>>>>>> sometime(~30minutes)) but the underlying sessions(~33 parallel sessions)
>>>>>>>> kept on running for 2hrs+, until then I saw ~2TB of temp space already
>>>>>>>> consumed and later it failed with insufficient temp space error.
>>>>>>>>
>>>>>>>>
>>>>>>>
>>>>>>

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