Re: "actual time" in QUERY PLAN for parallel operation when loops is bigger than 1

Wednesday, November 17, 2021 6:29 AM, nikolai.berkoff <nikolai.berkoff@pm.me> wrote:
>
> Parallel query is explained in
> https://www.postgresql.org/docs/14/how-parallel-query-works.html and
> https://www.postgresql.org/docs/14/parallel-plans.html
>
> The docs seem clear to me that as the nodes are executed in parallel then the
> time execution time is not 140.036*3. The 140.036 value is actual time the Parallel
> Seq Scan nodes ran for but there were up to 2 running in parallel.

Thanks for your reply.
I read your references but still confused about the 'loops' in parallel query result.

> ->  Parallel Seq Scan on c  (cost=0.00..8591.67 rows=416667 width=0) (actual time=0.030..140.036 rows=333333 loops=3)
In my previous example, actual row number is 333333*3=1e6(which is correct), so I think the actual time is 140.036*3ms.
Do your think the loops(3) has no meaning for parallel scan node when calculate actual time?