Horton

Re: [PoC] pg_upgrade: allow to upgrade publisher node

Masahiko Sawada <sawada.mshk@gmail.com>

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From: Masahiko Sawada <sawada.mshk@gmail.com>
To: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>, Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, vignesh C <vignesh21@gmail.com>, "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>, Peter Smith <smithpb2250@gmail.com>, Andres Freund <andres@anarazel.de>, Dilip Kumar <dilipbalaut@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Bruce Momjian <bruce@momjian.us>, Julien Rouhaud <rjuju123@gmail.com>
Date: 2023-11-28T19:30:37Z
Lists: pgsql-hackers 
On Tue, Nov 28, 2023 at 10:58 PM Hayato Kuroda (Fujitsu)
<kuroda.hayato@fujitsu.com> wrote:
>
> Dear Sawada-san,
>
> > On Tue, Nov 28, 2023 at 7:04 PM Hayato Kuroda (Fujitsu)
> > <kuroda.hayato@fujitsu.com> wrote:
> > >
> > >
> > > Yeah, we followed binary_upgrade_create_empty_extension(). Also, we set as
> > > un-strict to keep a caller function simpler.
> > >
> > > Currently get_old_cluster_logical_slot_infos() executes a query and it contains
> > > binary_upgrade_logical_slot_has_caught_up(). In pg_upgrade layer, we
> > assumed
> > > either true or false is returned.
> > >
> > > But if proisstrict is changed true, we must handle the case when NULL is
> > returned.
> > > It is small but backseat operation.
> >
> > Which cases are you concerned pg_upgrade could pass NULL to
> > binary_upgrade_logical_slot_has_caught_up()?
>
> Actually, we do not expect that it won't input NULL. IIUC all of slots have
> slot_name, and subquery uses its name. But will it be kept forever? I think we
> can avoid any risk.
>
> > I've not tested it yet but even if it returns NULL, perhaps
> > get_old_cluster_logical_slot_infos() would still set curr->caught_up
> > to false, no?
>
> Hmm. I checked the C99 specification [1] of strcmp, but it does not define the
> case when the NULL is input. So it depends implementation.

I think PQgetvalue() returns an empty string if the result value is null.

Regards,

-- 
Masahiko Sawada
Amazon Web Services: https://aws.amazon.com

Commits

  1. Fix issues in binary_upgrade_logical_slot_has_caught_up().

  2. Fix a random failure in 003_logical_slots.pl.

  3. Fix a test in 003_logical_slots.

  4. Fix uninitialized slot array access during the upgrade.

  5. Fix the test 003_logical_slots.

  6. Commit b195e6d482 forgot to update meson.build.

  7. Use shorter file names in the upgrade logical slots test.

  8. Migrate logical slots to the new node during an upgrade.

  9. Flush logical slots to disk during a shutdown checkpoint if required.

  10. Prevent possibility of panics during shutdown checkpoint.