On 05/31/2016 10:16 AM, Peter Geoghegan wrote:
> On Tue, May 31, 2016 at 10:10 AM, Josh berkus <josh@agliodbs.com> wrote:
>> "max_parallel_degree is the amount of parallelism in the query, with the
>> understanding that the original parent process counts as 1, which means
>> that if you set it to 1 you get no parallelism, and if you want 4
>> parallel workers you need to set it to 5."
>>
>> Which one of those is going to require more explanations on -general and
>> -novice? Bets?
>>
>> Let's not be complicated for the sake of being complicated.
>
> But the distinction between parallel workers and backends that can
> participate in parallel query does need to be user-visible. Worker
> processes are a commodity (i.e. the user must consider
> max_worker_processes).
It's still WAY simpler to understand "max_parallel is the number of
parallel workers I requested".
Any system where you set it to 2 and get only 1 worker on an idle system
is going to cause endless queries on the mailing lists.
--
--
Josh Berkus
Red Hat OSAS
(any opinions are my own)