Re: Is there any good optimization solution to improve the query efficiency?

Indices on TBL_RES.CID, TBL_RES.COD and the "join columns"?
Have you vacuumed and analyzed the tables lately?
Oliver's comment about first optimizing the individual subselects is also SOP.

On 6/5/23 01:56, gzh wrote:
>
> Hi everyone,
>
> I'm running into some performance issues with my SQL query.
> The following SQL query is taking a long time to execute.
>
> Execution Plan：
> explain analyse
> select * from TBL_RES
> left outer join(select T_CUST.RSNO RSNO2 ,
> T_CUST.KNO ,
> T_CUST.AGE ,
> T_CUST.GST
> from TBL_CUST T_CUST ,
> (select T_CUST.RSNO ,
> T_CUST.KNO ,
> MIN(T_CUST.GSTSEQ) GSTSEQ
> from TBL_CUST T_CUST ,
> TBL_POV T_POV ,
> TBL_RES T_RES
> where T_CUST.STSFLG = 'T'
> and T_CUST.DISPSEQ <> 9999
> AND T_CUST.KFIX = '0'
> and T_POV.CRSNO = T_RES.CRSNO
> and T_RES.RSNO = T_CUST.RSNO
> group by T_CUST.RSNO , T_CUST.KNO) T_POV2
> where T_POV2.RSNO = T_CUST.RSNO
> and T_POV2.KNO = T_CUST.KNO
> and T_POV2.GSTSEQ = T_CUST.GSTSEQ) T_POV3 on TBL_RES.RSNO = T_POV3.RSNO2
> and TBL_RES.KNO = T_POV3.KNO
> where TBL_RES.CID >= to_date('2022/07/01', 'YYYY/MM/DD')
> and TBL_RES.CID <= to_date('2022/07/31', 'YYYY/MM/DD')
> and TBL_RES.COD >= to_date('2022/07/01', 'YYYY/MM/DD')
> and TBL_RES.COD <= to_date('2022/07/31', 'YYYY/MM/DD')
> ----- Execution Plan -----
> Nested Loop Left Join  (cost=254388.44..452544.70 rows=473 width=3545)
> (actual time=3077.312..996048.714 rows=15123 loops=1)
>   Join Filter: ((TBL_RES.RSNO = T_CUST.RSNO) AND ((TBL_RES.KNO)::text =
> (T_CUST.KNO)::text))
>   Rows Removed by Join Filter: 4992268642
>   ->  Gather  (cost=1000.00..58424.35 rows=473 width=3489) (actual
> time=0.684..14.158 rows=15123 loops=1)
>         Workers Planned: 2
>         Workers Launched: 2
>         ->  Parallel Seq Scan on TBL_RES (cost=0.00..57377.05 rows=197
> width=3489) (actual time=0.096..279.504 rows=5041 loops=3)
>               Filter: ((CID >= to_date('2022/07/01'::text,
> 'YYYY/MM/DD'::text)) AND (CID <= to_date('2022/07/31'::text,
> 'YYYY/MM/DD'::text)) AND (COD >= to_date('2022/07/01'::text,
> 'YYYY/MM/DD'::text)) AND (COD <= to_date('2022/07/31'::text,
> 'YYYY/MM/DD'::text)))
>               Rows Removed by Filter: 161714
>   ->  Materialize  (cost=253388.44..394112.08 rows=1 width=56) (actual
> time=0.081..26.426 rows=330111 loops=15123)
>         ->  Hash Join  (cost=253388.44..394112.07 rows=1 width=56) (actual
> time=1197.484..2954.084 rows=330111 loops=1)
>               Hash Cond: ((T_CUST.RSNO = T_CUST_1.RSNO) AND
> ((T_CUST.KNO)::text = (T_CUST_1.KNO)::text) AND (T_CUST.gstseq =
> (min(T_CUST_1.gstseq))))
>               ->  Seq Scan on TBL_CUST T_CUST (cost=0.00..79431.15
> rows=2000315 width=61) (actual time=0.015..561.005 rows=2000752 loops=1)
>               ->  Hash  (cost=246230.90..246230.90 rows=262488 width=50)
> (actual time=1197.025..1209.957 rows=330111 loops=1)
>                     Buckets: 65536  Batches: 8  Memory Usage: 2773kB
>                     ->  Finalize GroupAggregate (cost=205244.84..243606.02
> rows=262488 width=50) (actual time=788.552..1116.074 rows=330111 loops=1)
>                           Group Key: T_CUST_1.RSNO, T_CUST_1.KNO
>                           ->  Gather Merge (cost=205244.84..238964.80
> rows=268846 width=50) (actual time=788.547..982.479 rows=330111 loops=1)
>                                 Workers Planned: 2
>                                 Workers Launched: 1
>                                 ->  Partial GroupAggregate 
> (cost=204244.81..206933.27 rows=134423 width=50) (actual
> time=784.032..900.979 rows=165056 loops=2)
>                                       Group Key: T_CUST_1.RSNO, T_CUST_1.KNO
>                                       ->  Sort (cost=204244.81..204580.87
> rows=134423 width=23) (actual time=784.019..833.791 rows=165061 loops=2)
>                                             Sort Key: T_CUST_1.RSNO,
> T_CUST_1.KNO
>                                             Sort Method: external merge 
> Disk: 5480kB
>                                             Worker 0: Sort Method:
> external merge  Disk: 5520kB
>                                             -> Parallel Hash Join 
> (cost=111758.80..190036.38 rows=134423 width=23) (actual
> time=645.302..716.247 rows=165061 loops=2)
>                                                   Hash Cond:
> (T_CUST_1.RSNO = T_RES.RSNO)
>                                                   -> Parallel Seq Scan on
> TBL_CUST T_CUST_1  (cost=0.00..74013.63 rows=204760 width=23) (actual
> time=0.018..264.390 rows=165058 loops=2)
> Filter: ((dispseq <> '9999'::numeric) AND ((stsflg)::text = 'T'::text) AND
> ((KFIX)::text = '0'::text))
> Rows Removed by Filter: 835318
>                                                   -> Parallel Hash 
> (cost=109508.52..109508.52 rows=137142 width=8) (actual
> time=343.593..343.896 rows=165058 loops=2)
> Buckets: 131072  Batches: 8  Memory Usage: 3008kB
> ->  Parallel Hash Join  (cost=51834.70..109508.52 rows=137142 width=8)
> (actual time=256.732..314.368 rows=165058 loops=2)
>     Hash Cond: ((T_RES.crsno)::text = (T_POV.crsno)::text)
>     ->  Parallel Seq Scan on TBL_RES T_RES (cost=0.00..53199.02
> rows=208902 width=17) (actual time=0.007..100.510 rows=250132 loops=2)
>     ->  Parallel Hash  (cost=49450.42..49450.42 rows=137142 width=9)
> (actual time=122.308..122.309 rows=165054 loops=2)
>           Buckets: 131072  Batches: 8  Memory Usage: 2976kB
>           ->  Parallel Seq Scan on TBL_POV T_POV (cost=0.00..49450.42
> rows=137142 width=9) (actual time=0.037..89.470 rows=165054 loops=2)
> Planning Time: 1.064 ms
> Execution Time: 996062.382 ms
> --------------------------------------------------------------------------------
>
> The amount of data in the table is as follows.
> TBL_RES    500265
> TBL_CUST   2000752
> TBL_POV    330109
>
> Any suggestions for improving the performance of the query would be
> greatly appreciated.
>
> Thanks in advance!
>

--
Born in Arizona, moved to Babylonia.