On Mon, 5 Jun 2023 at 18:56, gzh <gzhco...@126.com> wrote: > I'm running into some performance issues with my SQL query. > The following SQL query is taking a long time to execute.
> -> 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) The above join's selectivity estimation seems to be causing an upper join to resort to performing a Nested Loop join because the planner thinks the join will only produce 1 row. Unfortunately, extended statistics only help for base relation estimations and do nothing for join estimations, so your best bet might be to just: SET enable_nestloop TO off; for this query. David
