Re: postgresql-14 slow query - Mailing list pgsql-admin

Hello Team,

How can I tune this query? It got even slower when I created the index for (state_id, order_id desc). The following explain analyze output is without an index. It takes 13 seconds if I create that index. Could you help me?

Thank you so much for your help.

SELECT DISTINCT ON (order_history.order_id) order_id, order_history.creation_date  AS c_date
FROM work.order_history WHERE (order_history.state_id = ANY (ARRAY[30, 51, 63, 136, 195, 233, 348])) AND order_history.is_false = 0
ORDER BY order_history.order_id DESC;

EXPLAIN ANALYZE output:

 Unique  (cost=672007.46..1519683.55 rows=206423 width=12) (actual time=1701.420..3439.095 rows=2049357 loops=1)

   ->  Gather Merge  (cost=672007.46..1502346.48 rows=6934827 width=12) (actual time=1701.419..2989.243 rows=6891551 loops=1)
         Workers Planned: 4
         Workers Launched: 4
         ->  Sort  (cost=671007.40..675341.67 rows=1733707 width=12) (actual time=1657.609..1799.723 rows=1378310 loops=5)
               Sort Key: order_id DESC
               Sort Method: external merge  Disk: 38960kB
               Worker 0:  Sort Method: external merge  Disk: 31488kB
               Worker 1:  Sort Method: external merge  Disk: 36120kB
               Worker 2:  Sort Method: external merge  Disk: 31368kB
               Worker 3:  Sort Method: external merge  Disk: 36152kB

               ->  Parallel Seq Scan on order_history  (cost=0.00..473993.00 rows=1733707 width=12) (actual time=0.041..1211.485 rows=1378310 loops=5)
                     Filter: ((is_false = 0) AND (state_id = ANY ('{30,51,63,136,195,233,348}'::integer[])))
                     Rows Removed by Filter: 3268432
 Planning Time: 0.405 ms
 Execution Time: 3510.433 ms