Re: max_parallel_workers can't actually be set?

Hi,

On 2019-08-17 13:41:18 -0400, Tom Lane wrote:
> Try this:
> alter system set max_parallel_workers = 20;
> and restart the system.
> 
> max_parallel_workers is still 8, according to both SHOW and
> pg_controldata, nor can you launch more than 8 workers.

Hm. I can't reproduce that. I do get whatever number I configure.  Note
also that pg_controldata shows max_worker_processes, not
max_parallel_workers.


> Even odder, if you just do
> 
> regression=# set max_parallel_workers = 200;
> SET
> regression=# show max_parallel_workers;      
>  max_parallel_workers 
> ----------------------
>  200
> (1 row)
> 
> which should certainly not happen for a PGC_POSTMASTER parameter.

It's not PGC_POSTMASTER. That's max_worker_processes. The max_parallel_*
GUCs just control how many of max_worker_processes are used for $task.

Greetings,

Andres Freund