How to improve the performance of my SQL query？

Hi everyone,

I'm running into some performance issues with my SQL query.

The following SQL query is taking a long time to execute.

explain analyze

select COUNT(ET_CD)

from TBL_SHA

WHERE TBL_SHA.MS_CD = '009'

and TBL_SHA.ETRYS in

(select TBL_INF.RY_CD

from TBL_INF

WHERE TBL_INF.MS_CD = '009'

AND TBL_INF.RY_CD = '000001'

)

----- 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..0.030 rows=1 loops=1)

Index Cond: ((MS_CD = '009'::bpchar) AND (RY_CD = '000001'::bpchar))

Heap Fetches: 1

-> Seq Scan on TBL_SHA (cost=0.00..2698666.58 rows=3202774 width=18) (actual time=97264.138..123554.792 rows=3200000 loops=1)

Filter: ((MS_CD = '009'::bpchar) AND (ETRYS = '000001'::bpchar))

Rows Removed by Filter: 32000325

Planning Time: 0.162 ms

Execution Time: 124168.838 ms

--------------------------------------------------------------------------------

The index is defined as follows.

CREATE INDEX index_search_01 ON mdb.TBL_SHA USING btree (MS_CD, ETRYS);

When I take the following sql statement, the index works fine and the query is fast.

select COUNT(ET_CD)

from TBL_SHA

WHERE MS_CD = '009'

AND ETRYS = '000001'

The amount of data in the table is as follows.

TBL_SHA 38700325

TBL_INF 35546

Any suggestions for improving the performance of the query would be greatly appreciated.

Thanks in advance!