Re: Synchronizing slots from primary to standby

On Fri, Dec 29, 2023 at 12:32 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Fri, Dec 29, 2023 at 6:59 AM Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> >
> > On Wed, Dec 27, 2023 at 7:43 PM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > >
> > > >
> > > > 3) The slotsync worker uses primary_conninfo but also uses a new GUC
> > > > parameter, say slot_sync_dbname, to specify the database to connect.
> > > > The slot_sync_dbname overwrites the dbname if primary_conninfo also
> > > > specifies it. If both don't have a dbname, raise an error.
> > > >
> > >
> > > Would the users prefer to provide a value for a separate GUC instead
> > > of changing primary_conninfo? It is possible that we can have some
> > > users prefer to use one GUC and others prefer a separate GUC but we
> > > should add a new GUC if we are sure that is what users would prefer.
> > > Also, even if have to consider this option, I think we can easily
> > > later add a new GUC to provide a dbname in addition to having the
> > > provision of giving it in primary_conninfo.
> >
> > I think having two separate GUCs is more flexible for example when
> > users want to change the dbname to connect. It makes sense that the
> > slotsync worker wants to use the same connection string as the
> > walreceiver uses. But I guess today most primary_conninfo settings
> > that are set manually or are generated by tools such as pg_basebackup
> > don't have dbname. If we require a dbname in primary_conninfo, many
> > tools will need to be changed. Once the connection string is
> > generated, it would be tricky to change the dbname in it, as Shveta
> > mentioned. The users will have to carefully select the database to
> > connect when taking a base backup.
> >
>
> I see your point and agree that users need to be careful. I was trying
> to compare it with other places like the conninfo used with a
> subscription where no separate dbname needs to be provided. Now, here
> the situation is not the same because the same conninfo is used for
> different purposes (walreceiver doesn't require dbname (dbname is
> ignored even if present) whereas slotsyncworker requires dbname). I
> was just trying to see if we can avoid having a new GUC for this
> purpose. Does anyone else have an opinion on this matter?
>
> --
> With Regards,
> Amit Kapila.

Attaching the rebased patches. A recent commit 9a17be1e2 has resulted
in conflicts in pg_dump changes.

thanks
Shveta