Re: Add REPACK progress phases for logical decoding setup

On Wed, Sep 23, 2026 at 1:25 PM Sami Imseih <samimseih(dot)pg(at)gmail(dot)com> wrote:
>
> > I've reviewed the 0001 patch first as it's an open item. There are
> > some minor comments:
>
> Thanks!
>
> > - expected to be very brief.
> > + expected to be very brief, except for
> > + <command>REPACK (CONCURRENTLY)</command>, where it also covers enabling
> > + logical decoding and then initializing it. Enabling has nothing to do
> > + if <xref linkend="guc-effective-wal-level"/> is already
> > + <literal>logical</literal>; otherwise it waits for all backends to
> > + acknowledge that they started writing the additional WAL information
> > + that logical decoding requires. Initializing then waits for the
> >
> > The logical decoding activation waits for all processes to acknowledge
> > it, not only backends.
>
> Fair. I updated it.
>
> > + transactions that had already been assigned a transaction ID to end, so
> > + this phase can last as long as the longest of those transactions.
> >
> > During the logical decoding initialization, the snapshot builder also
> > has to wait for transactions that started after the initialization
> > began (i.e., those that started while it was in the BUILDING_SNAPSHOT
> > state). So this phase can last longer than the longest of the
> > transactions that
> > were running when it started. How about rephrasing it as follows?
> >
> > expected to be very brief, except for
> > <command>REPACK (CONCURRENTLY)</command>, where it also covers enabling
> > logical decoding and then initializing it. Enabling has nothing to do
> > if <xref linkend="guc-effective-wal-level"/> is already
> > <literal>logical</literal>; otherwise it waits for all processes to
> > acknowledge that they started writing the additional WAL information
> > that logical decoding requires. Initializing then waits for the
> > transactions that have been assigned a transaction ID to end,
> > including ones that started while this wait was in progress, so this
> > phase can last longer than the longest transaction running when the
> > command started.
>
> Good point. I used what you provided and I realized that in my v1 I was also
> specifically calling out that "waits for the transactions that have
> been assigned a transaction ID to end"
> also includes other REPACK CONCURRENTLY operations. This may not be obvious,
> so it's worth a callout.

Thank you for updating the patch! I've pushed the 0001 patch as it
looks good to me.

I'll review 0002 patch and send review comments.

Regards,

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