Re: Adding a '--clean-publisher-objects' option to 'pg_createsubscriber' utility.

On Tue, Feb 11, 2025 at 9:56 PM Shlok Kyal <shlok(dot)kyal(dot)oss(at)gmail(dot)com> wrote:
>
> On Tue, 11 Feb 2025 at 09:51, Shubham Khanna
> <khannashubham1197(at)gmail(dot)com> wrote:
> >
> > On Fri, Feb 7, 2025 at 7:46 AM Hayato Kuroda (Fujitsu)
> > <kuroda(dot)hayato(at)fujitsu(dot)com> wrote:
> > >
> > > Dear Shubham,
> > >
> > > Thanks for updating the patch.
> > >
> > > Previously you told that you had a plan to extend the patch to drop other replication
> > > objects [1], but I think it is not needed. pg_createsubscriber has already been
> > > able to drop the existing subscrisubscriptions in check_and_drop_existing_subscriptions().
> > > As for the replication slot, I have told in [2], it would be created intentionally
> > > thus I feel it should not be dropped.
> > > Thus I regard the patch does not have concrete extending plan.
> > >
> > > Below part contains my review comment.
> > >
> > > 01. Option name
> > >
> > > Based on the above discussion, "--cleanup-publisher-objects" is not suitable because
> > > it won't drop replication slots. How about "--cleanup-publications"?
> > >
> >
> > I have changed the name of the option to "--cleanup-existing-publications"
> >
> > > 02. usage()
> > > ```
> > > + printf(_(" -C --cleanup-publisher-objects drop all publications on the logical replica\n"));
> > > ```
> >
> > Fixed.
> >
> > > s/logical replica/subscriber
> > >
> > > 03. drop_all_publications
> > > ```
> > > +/* Drops all existing logical replication publications from all subscriber
> > > + * databases
> > > + */
> > > +static void
> > > ```
> > >
> > > Initial line of the comment must be blank [3].
> > >
> >
> > Removed this function.
> >
> > > 04. main
> > > ```
> > > + {"cleanup-publisher-objects", no_argument, NULL, 'C'},
> > > ```
> > >
> > > Is there a reason why upper case is used? I feel lower one is enough.
> > >
> >
> > Fixed.
> >
> > > 05. main
> > > ```
> > > + /* Drop publications from the subscriber if requested */
> > > + if (opt.cleanup_publisher_objects)
> > > + drop_all_publications(dbinfo);
> > > ```
> > >
> > > After considering more, I noticed that we have already called drop_publication()
> > > in the setup_subscriber(). Can we call drop_all_publications() there instead when
> > > -C is specified?
> > >
> >
> > I agree with you on this. I have removed the drop_all_publication()
> > and added the "--cleanup-existing-publications" option to the
> > drop_publication()
> >
> > > 06. 040_pg_createsubscriber.pl
> > >
> > > ```
> > > +$node_s->start;
> > > +# Create publications to test it's removal
> > > +$node_p->safe_psql($db1, "CREATE PUBLICATION test_pub FOR ALL TABLES;");
> > > +$node_p->safe_psql($db1, "CREATE PUBLICATION test_pub2 FOR ALL TABLES;");
> > > +
> > > +# Verify the existing publications
> > > +my $pub_count_before =
> > > + $node_s->safe_psql($db1, "SELECT COUNT(*) FROM pg_publication;");
> > > +is($pub_count_before, '2',
> > > + 'two publications created before --cleanup-publisher-objects is run');
> > > +
> > > +$node_s->stop;
> > > ```
> > >
> > > I feel it requires unnecessary startup and shutdown. IIUC, creating publications and check
> > > counts can be before stopping the node_s, around line 331.
> > >
> >
> > Fixed.
> >
> > > 07. 040_pg_createsubscriber.pl
> > >
> > > ```
> > > +$node_p->safe_psql($db1, "CREATE PUBLICATION test_pub FOR ALL TABLES;");
> > > +$node_p->safe_psql($db1, "CREATE PUBLICATION test_pub2 FOR ALL TABLES;");
> > > +
> > > +# Verify the existing publications
> > > +my $pub_count_before =
> > > + $node_s->safe_psql($db1, "SELECT COUNT(*) FROM pg_publication;");
> > > +is($pub_count_before, '2',
> > > + 'two publications created before --cleanup-publisher-objects is run');
> > > +
> > > ```
> > >
> > > Also, there is a possibility that CREATE PUBLICATION on node_p is not replicated yet
> > > when SELECT COUNT(*) is executed. Please wait for the replay.
> > >
> > > [1]: https://www.postgresql.org/message-id/CAHv8RjL4OvoYafofTb_U_JD5HuyoNowBoGpMfnEbhDSENA74Kg%40mail.gmail.com
> > > [2]: https://www.postgresql.org/message-id/OSCPR01MB1496664FDC38DA40A441F449FF5EE2%40OSCPR01MB14966.jpnprd01.prod.outlook.com
> > > [3]: https://www.postgresql.org/docs/devel/source-format.html
> > >
> >
> > Fixed.
> >
> > The attached Patch contains the suggested changes.
> >
>
> Hi Shubham,
>
> I have some comments for v4 patch:
> 1. I think we should update the comment for the function
> 'drop_publication'. As its usage is changed with this patch
> Currently it states:
> /*
> * Remove publication if it couldn't finish all steps.
> */
>

Fixed.

> 2. In case when --cleanup_existing_publications is not specified the
> info message has two double quotes.
>
> pg_createsubscriber: dropping publication
> ""pg_createsubscriber_5_aa3c31f2"" in database "postgres"
>
> The code:
> + appendPQExpBufferStr(targets,
> + PQescapeIdentifier(conn, dbinfo->pubname,
> + strlen(dbinfo->pubname)));
>
> It is appending the value along with the double quotes. I think we
> should assign the value of 'PQescapeIdentifier(conn, dbinfo->pubname,
> strlen(dbinfo->pubname)' to a string and then use it.
>

Fixed.

The attached patch contains the suggested changes.

Thanks and regards,
Shubham Khanna.