Horton

RE: releasing ParallelApplyTxnHash when pa_launch_parallel_worker returns NULL

Zhijie Hou (Fujitsu) <houzj.fnst@fujitsu.com>

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From: "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>
To: Ted Yu <yuzhihong@gmail.com>
Cc: "akapila@postgresql.org" <akapila@postgresql.org>, Postgres hackers <pgsql-hackers@lists.postgresql.org>
Date: 2023-01-11T03:55:25Z
Lists: pgsql-hackers 
On Wednesday, January 11, 2023 10:21 AM Ted Yu <yuzhihong@gmail.com> wrote:
>         /* First time through, initialize parallel apply worker state hashtable. */
>         if (!ParallelApplyTxnHash)
> 
> I think it would be better if `ParallelApplyTxnHash` is created by the first
> successful parallel apply worker.

Thanks for the suggestion. But I am not sure if it's worth to changing the
order here, because It will only optimize the case where user enable parallel
apply but never get an available worker which should be rare. And in such a
case, it'd be better to increase the number of workers or disable the parallel mode.

Best Regards,
Hou zj

Commits

  1. Avoid creating parallel apply state hash table unless required.