On Fri, 2023-07-21 at 09:43 +0800, gzh wrote:
> The definitions of the columns used in SQL are as follows.
>
> TBL_SHA
>
> ms_cd character(6) NOT NULL -- PRIMARY KEY
> et_cd character(8)
> etrys character(8)
>
> TBL_INF
>
> ms_cd character(6) NOT NULL -- PRIMARY KEY
> ry_cd character(8) NOT NULL -- PRIMARY KEY
>
> I made some modifications to the data, and I realized that I should not change the length of the data.
> The actual data and its corresponding execution plan are shown below.
>
> explain analyze
> select COUNT(ET_CD)
> from TBL_SHA
> WHERE TBL_SHA.MS_CD = 'MLD009'
> and TBL_SHA.ETRYS in
> (select TBL_INF.RY_CD
> from TBL_INF
> WHERE TBL_INF.MS_CD = 'MLD009'
> AND TBL_INF.RY_CD = '00000001'
> )
> ----- Execution Plan -----
> Limit (cost=2738709.57..2738709.58 rows=1 width=8) (actual time=124168.769..124168.771 rows=1 loops=1)
> -> Aggregate (cost=2738709.57..2738709.58 rows=1 width=8) (actual time=124168.767..124168.769 rows=1 loops=1)
> -> Nested Loop (cost=0.29..2730702.63 rows=3202774 width=9) (actual time=97264.166..123920.769 rows=3200000
loops=1)
> -> Index Only Scan using TBL_INF_pkc on TBL_INF (cost=0.29..8.31 rows=1 width=9) (actual
time=0.025..0.030rows=1 loops=1)
> Index Cond: ((MS_CD = 'MLD009'::bpchar) AND (RY_CD = '00000001'::bpchar))
> Heap Fetches: 1
> -> Seq Scan on TBL_SHA (cost=0.00..2698666.58 rows=3202774 width=18) (actual
time=97264.138..123554.792rows=3200000 loops=1)
> Filter: ((MS_CD = 'MLD009'::bpchar) AND (ETRYS = '00000001'::bpchar))
> Rows Removed by Filter: 32000325
> Planning Time: 0.162 ms
> Execution Time: 124168.838 ms
Thanks. That should definitely use a b-tree index defined on (ms_cd, etrsys).
Did you change any parameters that have an impact on query planning?
You can see that in the output of EXPLAIN (ANALYZE, BUFFERS, SETTINGS).
Yours,
Laurenz Albe
