On Thu, Jan 11, 2018 at 11:51 AM, Robert Haas <robertmh...@gmail.com> wrote: > I think the force_parallel_mode thing is too ugly to live. I'm not > sure that forcing low memory in workers is a thing we need to have, > but if we do, then we'll have to invent some other way to have it.
It might make sense to have the "minimum memory per participant" value come from a GUC, rather than be hard coded (it's currently hard-coded to 32MB). I don't think that it's that compelling as a user-visible option, but it might make sense as a testing option, that we might very well decide to kill before v11 is released (we might kill it when we come up with an acceptable interface for "just use this many workers" in a later commit, which I think we'll definitely end up doing anyway). By setting the minimum participant memory to 0, you can then rely on the parallel_workers table storage param forcing the number of worker processes that we'll request. You can accomplish the same thing with "min_parallel_table_scan_size = 0", of course. What do you think of that idea? To be clear, I'm not actually arguing that we need any of this. My point about being able to test low memory conditions from the first commit is that insisting on it is reasonable. I don't actually feel strongly either way, though, and am not doing any insisting myself. -- Peter Geoghegan
