On Sun, 5 Jan 2020 at 23:28, Amit Kapila <amit.kapil...@gmail.com> wrote: > > On Sun, Jan 5, 2020 at 7:38 PM Masahiko Sawada > <masahiko.saw...@2ndquadrant.com> wrote: > > > > On Sun, 5 Jan 2020 at 22:39, Tomas Vondra <tomas.von...@2ndquadrant.com> > > wrote: > > > > > > > > > So if we think we need an option to determine vacuum parallel degree, we > > > should have an option to disable parallelism too. I don't care much if > > > it's called DISABLE_PARALLEL, NOPARALLEL or PARALLEL 0, as long as we > > > make our mind and don't unnecessarily break it in the next release. > > > > > Fair point. I favor parallel 0 as that avoids adding more options and > also it is not very clear whether that is required at all. Till now, > if I see most people who have shared their opinion seems to favor this > as compared to another idea where we need to introduce more options. > > > > > Okay I got your point. It's just an idea but how about controlling > > parallel vacuum using two options. That is, we have PARALLEL option > > that takes a boolean value (true by default) and enables/disables > > parallel vacuum. And we have WORKERS option that takes an integer more > > than 1 to specify the number of workers. Of course we should raise an > > error if only WORKERS option is specified. WORKERS option is optional. > > If WORKERS option is omitted the number of workers is determined based > > on the number of indexes on the table. > > > > I think this would add failure modes without serving any additional > purpose. Sure, it might give the better feeling that we have separate > options to enable/disable parallelism and then specify the number of > workers with a separate option, but we already have various examples > as shared by me previously where setting the value as zero means the > option is disabled, so why to invent something new here?
I just felt it's not intuitive that specifying parallel degree to 0 means to disable parallel vacuum. But since majority of hackers seem to agree with this syntax I'm not going to insist on that any further. Regards, -- Masahiko Sawada http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
