On Mon, Jan 18, 2021 at 10:27 AM tsunakawa.ta...@fujitsu.com
<tsunakawa.ta...@fujitsu.com> wrote:
>
> From: Amit Kapila <amit.kapil...@gmail.com>
> > We already allow users to specify the degree of parallelism for all
> > the parallel operations via guc's max_parallel_maintenance_workers,
> > max_parallel_workers_per_gather, then we have a reloption
> > parallel_workers and vacuum command has the parallel option where
> > users can specify the number of workers that can be used for
> > parallelism. The parallelism considers these as hints but decides
> > parallelism based on some other parameters like if there are that many
> > workers available, etc. Why the users would expect differently for
> > parallel DML?
>
> I agree that the user would want to specify the degree of parallelism of DML, 
> too.  My simple (probably silly) question was, in INSERT SELECT,
>
> * If the target table has 10 partitions and the source table has 100 
> partitions, how would the user want to specify parameters?
>
> * If the source and target tables have the same number of partitions, and the 
> user specified different values to parallel_workers and parallel_dml_workers, 
> how many parallel workers would run?
>

Good question. I think if we choose to have a separate parameter for
DML, it can probably a boolean to just indicate whether to enable
parallel DML for a specified table and use the parallel_workers
specified in the table used in SELECT.

-- 
With Regards,
Amit Kapila.


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