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Re: Pgoutput not capturing the generated columns

Peter Smith <smithpb2250@gmail.com>

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From: Peter Smith <smithpb2250@gmail.com>
To: Shlok Kyal <shlok.kyal.oss@gmail.com>
Cc: Shubham Khanna <khannashubham1197@gmail.com>, Rajendra Kumar Dangwal <dangwalrajendra888@gmail.com>, pgsql-hackers@lists.postgresql.org, euler@eulerto.com
Date: 2024-06-05T00:18:53Z
Lists: pgsql-hackers 
On Mon, Jun 3, 2024 at 9:52 PM Shlok Kyal <shlok.kyal.oss@gmail.com> wrote:
>
> >
> > The attached Patch contains the suggested changes.
> >
>
> Hi,
>
> Currently, COPY command does not work for generated columns and
> therefore, COPY of generated column is not supported during tablesync
> process. So, in patch v4-0001 we added a check to allow replication of
> the generated column only if 'copy_data = false'.
>
> I am attaching patches to resolve the above issues.
>
> v5-0001: not changed
> v5-0002: Support COPY of generated column
> v5-0003: Support COPY of generated column during tablesync process
>

Hi Shlok, I have a question about patch v5-0003.

According to the patch 0001 docs "If the subscriber-side column is
also a generated column then this option has no effect; the replicated
data will be ignored and the subscriber column will be filled as
normal with the subscriber-side computed or default data".

Doesn't this mean it will be a waste of effort/resources to COPY any
column value where the subscriber-side column is generated since we
know that any copied value will be ignored anyway?

But I don't recall seeing any comment or logic for this kind of copy
optimisation in the patch 0003. Is this already accounted for
somewhere and I missed it, or is my understanding wrong?

======
Kind Regards,
Peter Smith.
Fujitsu Australia

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Doc: Generated column replication.

  2. Rename pubgencols_type to pubgencols in pg_publication.

  3. Doc: Fix column name in pg_publication catalog.

  4. Fix buildfarm failure introduced by commit e65dbc9927.

  5. Change publication's publish_generated_columns option type to enum.

  6. Fix \dRp+ output when describing publications with a lower server version.

  7. Replicate generated columns when 'publish_generated_columns' is set.

  8. Doc: Update the behavior of generated columns in Logical Replication.

  9. Replicate generated columns when specified in the column list.

  10. Doc: Generated columns are skipped for logical replication.