On Fri, Nov 18, 2022 at 1:47 PM Amit Kapila <amit.kapil...@gmail.com> wrote: > > On Fri, Nov 18, 2022 at 8:01 AM Peter Smith <smithpb2...@gmail.com> wrote: > > > > On Fri, Nov 18, 2022 at 11:36 AM Masahiko Sawada <sawada.m...@gmail.com> > > wrote: > > > > > ... > > > --- > > > The streaming parameter has the new value "parallel" for "streaming" > > > option to enable the parallel apply. It fits so far but I think the > > > parallel apply feature doesn't necessarily need to be tied up with > > > streaming replication. For example, we might want to support parallel > > > apply also for non-streaming transactions in the future. It might be > > > better to have another option, say "parallel", to control parallel > > > apply behavior. The "parallel" option can be a boolean option and > > > setting parallel = on requires streaming = on. > > > > > If we do that then how will the user be able to use streaming > serialize mode (write to file for streaming transactions) as we have > now? Because after we introduce parallelism for non-streaming > transactions, the user would want parallel = on irrespective of the > streaming mode. Also, users may wish to only parallelize large > transactions because of additional overhead for non-streaming > transactions for transaction dependency tracking, etc. So, the user > may wish to have a separate knob for large transactions as the patch > has now.
One idea for that would be to make it enum. For example, setting parallel = "streaming" works for that. > > > > > FWIW, I tend to agree with this idea but for a different reason. In > > this patch, the 'streaming' parameter had become a kind of hybrid > > boolean/enum. AFAIK there are no other parameters anywhere that use a > > hybrid pattern like this so I was thinking it may be better not to be > > different. > > > > I think we have a similar pattern for GUC parameters like > constraint_exclusion (see constraint_exclusion_options), > backslash_quote (see backslash_quote_options), etc. Right. vacuum_index_cleanup and buffering storage parameters that accept 'on', 'off', or 'auto') are other examples. Regards, -- Masahiko Sawada Amazon Web Services: https://aws.amazon.com