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

Did you try forcing the opt_estimate hint to influence the cte estimation to increase 18 times as Jonathan suggested? Does that change anything in the execution path?

On Wed, 16 Nov, 2022, 11:24 pm yudhi s, <learnerdatabase99_at_gmail.com> wrote:

> Extremely sorry, as it looks like I have messed it up. Trying to correct
> it.
>
> Basically we had a sql profile attached in past while we were in version
> 11.2.0.4 and was working fine. also when we moved to 19.11 too that same
> profile was there making the query finish without any issue. but that same
> plan is now making the query to go for consuming terabytes of temp on
> version 19.15. I dont have a sql monitor from 19.11 plan which was
> succeeding fine, but its the same plan phv as the 19.15 plan which i posted
> below in the 2nd sql monitor.
>
> However, the point i want to make here is , all of these plans are almost
> same with minor difference. And If you see the specific section of the plan
> which does the "HASH JOIN OUTER" and passing the resulting output to the
> analytical function is exactly same in all these cases but still the 19.15
> version is going for ~1TB+ temp. So its definitely odd.
>
> Below is the three comparison of that exact section of the plan which is
> playing key role here in consuming all tempspace. In the first case even if
> the ~7Billion rows in getting sorted using just ~10GB of tempspace, whereas
> in second and third cases its using in TBs. Though the data volume is
> higher but this excessive use of tempspace is not justified. Definitely
> seems buggy.
>
> https://gist.github.com/databasetech0073/55c5722da8105dfcc647ab3bd1b24a48
>
> And also as you have highlighted the bug related to bloom filter i tried
> forcing the (no_px_join_filter hints and even setting up
> "_bloom_filter_enabled" and "_bloom_pruning_enabled" in session level to
> stop the bloom pruning and tried running SELECT part of the query, but
> still its using same excessive amount of tempspace.
>
>
> --1st sqlmonitor
>
> Below is the sql monitor and outline in version 11.2.0.4, which was
> finishing by consuming <20GB tempspace.
>
> https://gist.github.com/databasetech0073/630dad9fc43d6ab6c8863251e29f1cf2
>
> --2nd sql monitor
>
> Below is the sql monitor and outline in version 19.15 (by forcing exactly
> the same plan through a sql profile as it used to take in 11.2).
>
> https://gist.github.com/databasetech0073/37ec33e73a23bd0055148ba43a0a49ca
>
> --3rd sql monitor
>
> Below is the sql monitor and outline in current version ( i.e 19.15
> without any profile) which is also consuming high tempspace.
>
> https://gist.github.com/databasetech0073/4b895f5790a993ed326d389b54295f9b
>
>
>
>
> On Tue, 15 Nov, 2022, 6:39 pm Jonathan Lewis, <jlewisoracle_at_gmail.com>
> wrote:
>
>>
>> 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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