Re: postgresql-14 slow query

I would move the WHERE filter into a subquery and then run the ORDER BY/DISTINCT on the subquery result.  I like to
avoidDISTINCT on queries using an  ANTIJOIN or SEMIJOIN if possible.  It is hard to recommend without knowing your
data.

Sent from my iPhone

> On Apr 15, 2022, at 4:59 PM, Kenny Bachman <kenny.bachman17@gmail.com> wrote:
>
> 
> 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
explainanalyze 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..1211.485rows=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