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

From: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
To: Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com>
Cc: "Hayato Kuroda (Fujitsu)" <kuroda(dot)hayato(at)fujitsu(dot)com>, Dilip Kumar <dilipbalaut(at)gmail(dot)com>, "Zhijie Hou (Fujitsu)" <houzj(dot)fnst(at)fujitsu(dot)com>, Peter Smith <smithpb2250(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Bruce Momjian <bruce(at)momjian(dot)us>, Julien Rouhaud <rjuju123(at)gmail(dot)com>, vignesh C <vignesh21(at)gmail(dot)com>, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>
Subject: Re: [PoC] pg_upgrade: allow to upgrade publisher node
Date: 2023-09-22 06:44:38
Message-ID: CAA4eK1LEzkGP441z=4hkK4vn5T3m1kzndoOw0TtxmyaY=ZBeJQ@mail.gmail.com
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On Fri, Sep 22, 2023 at 11:59 AM Bharath Rupireddy
<bharath(dot)rupireddyforpostgres(at)gmail(dot)com> wrote:
>
> On Thu, Sep 21, 2023 at 6:54 PM Hayato Kuroda (Fujitsu)
> <kuroda(dot)hayato(at)fujitsu(dot)com> wrote:
> >
>
> 1.
> + /*
> + * Use max_slot_wal_keep_size as -1 to prevent the WAL removal by the
> + * checkpointer process. If WALs required by logical replication slots
> + * are removed, the slots are unusable. This setting prevents the
> + * invalidation of slots during the upgrade. We set this option when
>
> IIUC, during upgrade we don't want the checkpointer to remove WAL that
> may be needed by logical slots, for that the patch overrides the user
> set value for max_slot_wal_keep_size. What if the WAL is removed
> because of the wal_keep_size setting?
>

We are fine with the WAL removal unless it can invalidate the slots
which is prevented by max_slot_wal_keep_size.

>
> 3. Does this patch support upgrading of logical replication slots on a
> streaming standby?
>

No, and a note has been added by the patch for the same.

--
With Regards,
Amit Kapila.

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