Thank you so much Andy and Lok.
On Mon, Nov 22, 2021 at 12:42 AM Lok P <loknath.73@xxxxxxxxx> wrote:
I think you should fix the buggy code first as Andrew suggested as that is
not anyway as per your business logic. However, there was a bug in 11.2 wrt
cell smart scan disabled for DML. So mostly you are not seeing cell offload
because of that. And fix for that would be either force the smartscan using
_serial_direct_read to force true before this update or make it bulk update
so that this querying part can be converted to cursor select query so that
you will be benefited of cell smartscan automatically.
On Sun, 21 Nov 2021, 2:40 am Pap, <oracle.developer35@xxxxxxxxx> wrote:
Thank you so much Andy.
Never thought of this , that RID was supposed to come from the FROM
section of the query only. but as in this case , it's not available there
so oracle is doing something like ( GTT_TAB.RID = GTT_TAB.RID). So
basically in current query it must be updating all the rows in the GTT_TAB
which is definitely not the logic as i am seeing the comment section for
that query stating its there to update top ~20 RID'S only based on
difference in run time (i.e. je_ets-je_sts desc).
With respect to the amount of CPU time consumption in the FTS of table
MRQ(and unavailability of any cell offloading percentage in sql monitor in
that step) , is that expected. I was trying to understand , if after
the fix, it will scan the table ~20 times , then if that behaviour is
expected one or still any issue with that?
On Sun, Nov 21, 2021 at 1:58 AM Andy Sayer <andysayer@xxxxxxxxx> wrote:
" There is no such column as 'RID' in table MRQ, but this UPDATE runs
without error in production"
Then it is probably not doing what was probably intended and you should
fix that before even considering making it faster.
You should always specify where columns are supposed to be coming from.
For:
UPDATE GTT_TAB
SET PRT = 999
WHERE RID IN
(SELECT RID..
If RID cannot be found in that subquery, it will be treated as if you
meant it to come from GTT_TAB. This is probably not what you wanted.
Follow best practice and specify where the columns are coming from, do:
UPDATE GTT_TAB
SET GTT_TAB.PRT = 999
WHERE GTT_TAB.RID IN
(SELECT sq.RID
FROM ( SELECT mrq.rid -- I've also removed the select *
here
FROM MRQ
WHERE mrq.R_DATE = TRUNC ( :B1) - 2
AND mrq.RP_STX = 'XX'
AND mrq.MRF_NM = 'YYY'
AND mrq.FR_NM NOT IN
(SELECT tlsv.L_VL
FROM TLSV
WHERE tlsv.L_NM = 'XXXXXXX')
ORDER BY mrq.JE_ETS - mrq.JE_STS DESC) sq
WHERE ROWNUM <= 20)
You will get the expected error before it tries to execute that subquery
for every single row in GTT_TAB.
Thanks,
Andy
On Sat, 20 Nov 2021 at 20:14, Pap <oracle.developer35@xxxxxxxxx> wrote:
Hi, We have the below update query running for 4-5hrs on 11.2.0.4
version Oracle database impacting one customer process. and it seems almost
all the time has been spent on step- 11. And also that step is getting full
scanned and executed ~13K times. It's updating a global temporary
table-GTT_TAB. This plan line id-11 is all on CPU, not able to understand
why?
Another odd behaviour related to this:- There is no such column as
'RID' in table MRQ, but this UPDATE runs without error in production. When
we try to execute the SELECT part of the query(i.e. SELECT RID...) It's
failing with "ORA-00904: "RID": invalid identifier" . So I wanted to
understand , how did that Update happen/succeed then? I have captured the
sql monitor for the same as below from prod. In any case, I was expecting
the plan_line_id -7 ( SORT ORDER BY STOPKEY ) should have returned
only ~20 actual rows(as we have rownum<=20 filter) and thus the table MRQ
would have been full scanned Max ~20 times , but it's resulting ~13k rows
and that many time the MRQ is getting full scanned. Are we hitting any bugs
here because of the buggy way it's written by the team?
Also the execution time for this Update query is increasing day by day,
must be because either the table GTT_TAB is having rows increasing day by
day and thus the number of full tables scan increases for MRQ making the
query response time increase. or the number of rows in table MRQ is
increasing thus making that step-11 more CPU intensive for each full scan.
Below is the table and column stats.
Table MRQ having total ~2.3million rows.
COLUMN_NAME NUM_DISTINCT DENSITY
NUM_NULLS HISTOGRAM
RP_STX 6
2.11625295890333E-7 0
FREQUENCY
R_DATE 395
0.0048780487804878 0
HEIGHT BALANCED
MRF_NM 4
2.11625295890333E-7 0
FREQUENCY
FR_NM 30
2.11625295890333E-7 0
FREQUENCY
Table TSLV is a static data table holding just ~1099 rows. An index -
TLSV_IX2 is on column L_NM. And the L_NM column has ~416 distinct values.
UPDATE GTT_TAB
SET PRT = 999
WHERE RID IN
(SELECT RID
FROM ( SELECT *
FROM MRQ
WHERE R_DATE = TRUNC ( :B1) - 2
AND RP_STX = 'XX'
AND MRF_NM = 'YYY'
AND FR_NM NOT IN
(SELECT L_VL
FROM TLSV
WHERE L_NM = 'XXXXXXX')
ORDER BY JE_ETS - JE_STS DESC)
WHERE ROWNUM <= 20)
Global Information
------------------------------
Status : DONE
Instance ID : 4
SQL Execution ID : 67108864
Execution Started : 11/18/2021 18:15:25
First Refresh Time : 11/18/2021 18:15:32
Last Refresh Time : 11/18/2021 23:25:30
Duration : 18605s
Binds
========================================================================================================================
| Name | Position | Type |
Value |
========================================================================================================================
| :B1 | 1 | DATE | 11/19/2021 00:00:00
|
========================================================================================================================
Global Stats
============================================================================================
| Elapsed | Cpu | IO | Concurrency | Cluster | Other |
Buffer | Read | Read |
| Time(s) | Time(s) | Waits(s) | Waits(s) | Waits(s) | Waits(s) |
Gets | Reqs | Bytes |
============================================================================================
| 18605 | 18594 | 0.10 | 0.01 | 0.10 | 10 |
4G | 219 | 19MB |
============================================================================================
SQL Plan Monitoring Details (Plan Hash Value=3480899078)
=======================================================================================================================================================================================
| Id | Operation | Name |
Rows | Cost | Time | Start | Execs | Rows | Read | Read |
Mem | Activity | Activity Detail |
| | | |
(Estim) | | Active(s) | Active | | (Actual) | Reqs | Bytes |
(Max) | (%) | (# samples) |
=======================================================================================================================================================================================
| 0 | UPDATE STATEMENT | |
| | | | 1 | | | |
| | |
| 1 | UPDATE | GTT_TAB |
| | 18599 | +7 | 1 | 0 | | |
| 0.01 | log file sync (1) |
| 2 | FILTER | |
| | 18599 | +7 | 1 | 13792 | | |
| | |
| 3 | TABLE ACCESS STORAGE FULL | GTT_TAB |
12302 | 70 | 18599 | +7 | 1 | 13792 | 40 | 18MB |
| | |
| 4 | FILTER | |
| | 18599 | +7 | 13792 | 13792 | | |
| | |
| 5 | COUNT STOPKEY | |
| | 18599 | +7 | 13792 | 13792 | | |
| | |
| 6 | VIEW | |
1122 | 52521 | 18599 | +7 | 13792 | 13792 | | |
| | |
| 7 | SORT ORDER BY STOPKEY | |
1122 | 52521 | 18599 | +7 | 13792 | 13792 | | |
96256 | 1.89 | Cpu (342) |
| 8 | HASH JOIN RIGHT ANTI NA | |
1122 | 52520 | 18599 | +7 | 13792 | 255M | | |
675K | 0.17 | Cpu (30) |
| 9 | TABLE ACCESS BY INDEX ROWID | TLSV |
1 | 2 | 18599 | +7 | 13792 | 68960 | 116 | 928KB |
| | |
| 10 | INDEX RANGE SCAN | TLSV_IX2 |
1 | 1 | 18599 | +7 | 13792 | 68960 | | |
| | |
| 11 | TABLE ACCESS STORAGE FULL | MRQ |
1202 | 52518 | 18604 | +2 | 13792 | 255M | 47 | 376KB |
| 97.94 | Cpu (17744) |
=======================================================================================================================================================================================
