Re: Make default subscription streaming option as Parallel

On Mon, Oct 21, 2024 at 5:09 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Mon, Oct 7, 2024 at 4:03 PM vignesh C <vignesh21(at)gmail(dot)com> wrote:
> >
> > On Mon, 7 Oct 2024 at 12:26, Hayato Kuroda (Fujitsu)
> > <kuroda(dot)hayato(at)fujitsu(dot)com> wrote:
> >
> > > One comment for your patch;
> > > Shouldn't we add a streaming=off case for pg_dump test? You added lines but no one
> > > passes it.
> > >
> >
> > Update existing pg_dump tests to cover the streaming options, the
> > attached patch has the changes for the same.
> >
>
> @@ -5235,6 +5235,8 @@ dumpSubscription(Archive *fout, const
> SubscriptionInfo *subinfo)
> appendPQExpBufferStr(query, ", streaming = on");
> else if (strcmp(subinfo->substream, "p") == 0)
> appendPQExpBufferStr(query, ", streaming = parallel");
> + else
> + appendPQExpBufferStr(query, ", streaming = off");
>
> For newer versions (>=18), we shouldn't need to specify "streaming =
> parallel" while creating a subscription as that will be the default.
> However, with the above code pg_dump statements will still have that.
> There is nothing wrong with that but ideally, it won't be required.
> Now, OTOH, doing that would require some version-handling code, which
> is nothing new for pg_dump but not sure it makes sense for this
> particular case. Another related point is that normally we don't
> recommend people to use dump generated with pg_dump to use with lower
> server versions than pg_dump itself, but the current proposed patch
> will allow that. However, if we change it as I am saying that won't be
> possible.

Leaving the patch as-is seems better to me.

PROS
- The simple code explicitly setting all parameter values is easy to
understand as-is.
- AFAICT it works for all that the pg_dump docs [1] guarantees.
- No version handling code will be needed...
- Therefore, no risk of accidentally introducing any versioning bugs.
- Yields a more portable dump file (even though not guaranteed by pg_dump docs)

CONS
- A few more chars in the dump file?
- What else?

======
[1] https://www.postgresql.org/docs/devel/app-pgdump.html

Kind Regards,
Peter Smith.
Fujitsu Australia