Re: Identify missing publications from publisher while create/alter subscription.

I have spent little time looking at the latest patch. The patch looks
to be in good shape as it has already been reviewed by many people
here, although I did get some comments. Please take a look and let me
know your thoughts.


+   /* Try to connect to the publisher. */
+   wrconn = walrcv_connect(sub->conninfo, true, sub->name, &err);
+   if (!wrconn)
+       ereport(ERROR,
+               (errmsg("could not connect to the publisher: %s", err)));

I think it would be good to also include the errcode
(ERRCODE_CONNECTION_FAILURE) here?

--

@@ -514,6 +671,8 @@ CreateSubscription(ParseState *pstate,
CreateSubscriptionStmt *stmt,

        PG_TRY();
        {
+           check_publications(wrconn, publications, opts.validate_publication);
+


Instead of passing the opts.validate_publication argument to
check_publication function, why can't we first check if this option is
set or not and accordingly call check_publication function? For other
options I see that it has been done in the similar way for e.g. check
for opts.connect or opts.refresh or opts.enabled etc.

--

Above comment also applies for:

@@ -968,6 +1130,8 @@ AlterSubscription(ParseState *pstate,
AlterSubscriptionStmt *stmt,
                replaces[Anum_pg_subscription_subpublications - 1] = true;

                update_tuple = true;
+               connect_and_check_pubs(sub, stmt->publication,
+                                      opts.validate_publication);


--

+         <para>
+          When true, the command verifies if all the specified publications
+          that are being subscribed to are present in the publisher and throws
+          an error if any of the publication doesn't exist. The default is
+          <literal>false</literal>.

publication -> publications (in the 4th line : throw an error if any
of the publication doesn't exist)

This applies for both CREATE and ALTER subscription commands.

--
With Regards,
Ashutosh Sharma.

On Sat, Nov 13, 2021 at 12:50 PM vignesh C <vignesh21@gmail.com> wrote:
>
> On Wed, Nov 10, 2021 at 11:16 AM Bharath Rupireddy
> <bharath.rupireddyforpostgres@gmail.com> wrote:
> >
> > On Tue, Nov 9, 2021 at 9:27 PM vignesh C <vignesh21@gmail.com> wrote:
> > > Attached v12 version is rebased on top of Head.
> >
> > Thanks for the patch. Here are some comments on v12:
> >
> > 1) I think ERRCODE_TOO_MANY_ARGUMENTS isn't the right error code, the
> > ERRCODE_UNDEFINED_OBJECT is more meaningful. Please change.
> > + ereport(ERROR,
> > + (errcode(ERRCODE_TOO_MANY_ARGUMENTS),
> > + errmsg_plural("publication %s does not exist in the publisher",
> > +    "publications %s do not exist in the publisher",
> >
> > The existing code using
> >         ereport(ERROR,
> >                 (errcode(ERRCODE_UNDEFINED_OBJECT),
> >                  errmsg("subscription \"%s\" does not exist", subname)));
>
> Modified
>
> > 2) Typo: It is "One of the specified publications exists."
> > +# One of the specified publication exist.
>
> Modified
>
> > 3) I think we can remove the test case "+# Specified publication does
> > not exist." because the "+# One of the specified publication exist."
> > covers the code.
>
> Modified
>
> > 4) Do we need the below test case? Even with refresh = false, it does
> > call connect_and_check_pubs() right? Please remove it.
> > +# Specified publication does not exist with refresh = false.
> > +($ret, $stdout, $stderr) = $node_subscriber->psql('postgres',
> > +       "ALTER SUBSCRIPTION mysub1 SET PUBLICATION non_existent_pub
> > WITH (REFRESH = FALSE, VALIDATE_PUBLICATION = TRUE)"
> > +);
> > +ok( $stderr =~
> > +         m/ERROR:  publication "non_existent_pub" does not exist in
> > the publisher/,
> > +       "Alter subscription for non existent publication fails");
> > +
>
> Modified
>
> > 5) Change the test case names to different ones instead of the same.
> > Have something like:
> > "Create subscription fails with single non-existent publication");
> > "Create subscription fails with multiple non-existent publications");
> > "Create subscription fails with mutually exclusive options");
> > "Alter subscription add publication fails with non-existent publication");
> > "Alter subscription set publication fails with non-existent publication");
> > "Alter subscription set publication fails with connection to a
> > non-existent database");
>
> Modified
>
> Thanks for the comments, the attached v13 patch has the fixes for the same.
>
> Regards,
> Vignesh