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Re: Perform streaming logical transactions by background workers and parallel apply

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Peter Smith <smithpb2250@gmail.com>
Cc: "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>, shveta malik <shveta.malik@gmail.com>, "wangw.fnst@fujitsu.com" <wangw.fnst@fujitsu.com>, "shiy.fnst@fujitsu.com" <shiy.fnst@fujitsu.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Dilip Kumar <dilipbalaut@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>
Date: 2023-01-24T04:42:37Z
Lists: pgsql-hackers 
On Tue, Jan 24, 2023 at 9:13 AM Peter Smith <smithpb2250@gmail.com> wrote:
>
> 1.
>
> IIUC the GUC name was made generic 'logical_replication_mode' so that
> multiple developer GUCs are not needed later.
>
> But IMO those current option values (buffered/immediate) for that GUC
> are maybe a bit too generic. Perhaps in future, we might want more
> granular control than that allows. e.g. I can imagine there might be
> multiple different meanings for what "buffered" means. If there is any
> chance of the generic values being problematic later then maybe they
> should be made more specific up-front.
>
> e.g. maybe like:
> logical_replication_mode = buffered_decoding
> logical_replication_mode = immediate_decoding
>

For now, it seems the meaning of buffered/immediate suits our
debugging and test needs for publisher/subscriber. This is somewhat
explained in Shveta's email [1]. I also think in the future this
parameter could be extended for a different purpose but maybe it would
be better to invent some new values at that time as things would be
more clear. We could do what you are suggesting or in fact even use
different values for publisher and subscriber but not really sure
whether that will simplify the usage.

[1] - https://www.postgresql.org/message-id/CAJpy0uDzddK_ZUsB2qBJUbW_ZODYGoUHTaS5pVcYE2tzATCVXQ%40mail.gmail.com

-- 
With Regards,
Amit Kapila.

Commits

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  1. Fix invalid memory access during the shutdown of the parallel apply worker.

  2. Fix assertion failure in apply worker.

  3. Use elog to report unexpected action in handle_streamed_transaction().

  4. Use appropriate wait event when sending data in the apply worker.

  5. Allow the logical_replication_mode to be used on the subscriber.

  6. Rename GUC logical_decoding_mode to logical_replication_mode.

  7. Display the leader apply worker's PID for parallel apply workers.

  8. Improve the code to decide and process the apply action.

  9. Document the newly added wait events added by commit 216a784829.

  10. Perform apply of large transactions by parallel workers.

  11. Wake up a subscription's replication worker processes after DDL.

  12. Add copyright notices to meson files

  13. Better document logical replication parameters

  14. Add a common function to generate the origin name.

  15. Harmonize parameter names in storage and AM code.

  16. Avoid using list_length() to test for empty list.

  17. Improve two comments related to a boolean DefElem's value

  18. Fix partition table's REPLICA IDENTITY checking on the subscriber.

  19. Fix data inconsistency between publisher and subscriber.

  20. Fix cache look-up failures while applying changes in logical replication.