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

Thank you Mark. Actually the issue we are having is suddenly post migration to oracle 19.15 from 19.11 the temp space consumption for evaluating an analytical function has been increased( it's going beyond ~3 terabyte+) for similar volume of input data and it's making the query to fail with insufficient temp space error. We are trying to see if any possible way the temp spill can be minimized. And also I can't think of, how a missing storage index would play a role here.

On Thu, 17 Nov, 2022, 5:55 pm Mark W. Farnham, <mwf_at_rsiz.com> wrote:

> Without looking at much of the thread, is it possible that you have
> storage indexes that have become invalid?
>
>
>
> Other than a side effect of delivering pant loads of data to the compute
> engine for filtering there when they might being valid have slenderized
> data retrieval significantly, my recollection is that no complaint will be
> in the traces. This could be completely off target and may not be related
> to your case at all, but it should not take much effort to look.
>
>
>
> *From:* oracle-l-bounce_at_freelists.org [mailto:
> oracle-l-bounce_at_freelists.org] *On Behalf Of *yudhi s
> *Sent:* Wednesday, November 16, 2022 1:44 PM
> *To:* Lok P
> *Cc:* Jonathan Lewis; Oracle L
> *Subject:* Re: high temp space usage for same analytic function on latest
> version
>
>
>
> Yes I tried that and it does increase the estimates for the cte from 38k
> to 860k but that problematic section of the plan remains same consuming
> terabytes of temp space.
>
>
>
> On Thu, 17 Nov, 2022, 12:10 am Lok P, <loknath.73_at_gmail.com> wrote:
>
> 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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