Re: Have pg_basebackup write "dbname" in "primary_conninfo"?

On Mon, 11 Mar 2024 at 17:16, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>
> On Tue, Feb 27, 2024 at 2:07 PM Hayato Kuroda (Fujitsu)
> <kuroda(dot)hayato(at)fujitsu(dot)com> wrote:
> >
> > > PSA the patch for implementing it. It is basically same as Ian's one.
> > > However, this patch still cannot satisfy the condition 3).
> > >
> > > `pg_basebackup -D data_N2 -d "user=postgres" -R`
> > > -> dbname would not be appeared in primary_conninfo.
> > >
> > > This is because `if (connection_string)` case in GetConnection() explicy override
> > > a dbname to "replication". I've tried to add a dummy entry {"dbname", NULL} pair
> > > before the overriding, but it is no-op. Because The replacement of the dbname in
> > > pqConnectOptions2() would be done only for the valid (=lastly specified)
> > > connection options.
> >
> > Oh, this patch missed the straightforward case:
> >
> > pg_basebackup -D data_N2 -d "user=postgres dbname=replication" -R
> > -> dbname would not be appeared in primary_conninfo.
> >
> > So I think it cannot be applied as-is. Sorry for sharing the bad item.
> >
>
> Can you please share the patch that can be considered for review?

Here is a patch with few changes: a) Removed the version check based
on discussion from [1] b) updated the documentation.
I have tested various scenarios with the attached patch, the dbname
that is written in postgresql.auto.conf for each of the cases with
pg_basebackup is given below:
1) ./pg_basebackup -U vignesh -R
-> primary_conninfo = "dbname=vignesh" (In this case primary_conninfo
will have dbname as username specified)
2) ./pg_basebackup -D data -R
-> primary_conninfo = "dbname=vignesh" (In this case primary_conninfo
will have the dbname as username (which is the same as the OS user
while setting defaults))
3) ./pg_basebackup -d "user=vignesh" -D data -R
-> primary_conninfo = "dbname=replication" (In this case
primary_conninfo will have dbname as replication which is the default
value from GetConnection as connection string is specified)
4) ./pg_basebackup -d "user=vignesh dbname=postgres" -D data -R
-> primary_conninfo = "dbname=postgres" (In this case primary_conninfo
will have the dbname as the dbname specified)
5) ./pg_basebackup -d "" -D data -R
-> primary_conninfo = "dbname=replication" (In this case
primary_conninfo will have dbname as replication which is the default
value from GetConnection as connection string is specified)

I have mentioned the reasons as to why dbname is being set to
replication or username in each of the cases. How about replacing
these values in postgresql.auto.conf manually.

[1] - https://www.postgresql.org/message-id/CAGECzQTh9oB3nu98DsHMpRaVaqXPDRgTDEikY82OAKYF0%3DhVMA%40mail.gmail.com

Regards,
Vignesh