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

Zhijie Hou (Fujitsu) <houzj.fnst@fujitsu.com>

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From: "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: Masahiko Sawada <sawada.mshk@gmail.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>, Peter Smith <smithpb2250@gmail.com>
Date: 2023-02-03T03:29:27Z
Lists: pgsql-hackers

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On Friday, February 3, 2023 11:04 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
> 
> On Thu, Feb 2, 2023 at 4:52 AM Peter Smith <smithpb2250@gmail.com>
> wrote:
> >
> > Some minor review comments for v91-0001
> >
> 
> Pushed this yesterday after addressing your comments!

Thanks for pushing.

Currently, we have two remaining patches which we are not sure whether it's worth
committing for now. Just share them here for reference.

0001:

Based on our discussion[1] on -hackers, it's not clear that if it's necessary
to add the sub-feature to stop extra worker when
max_apply_workers_per_suibscription is reduced. Because:

- it's not clear whether reducing the 'max_apply_workers_per_suibscription' is very
  common.
- even when the GUC is reduced, at that point in time all the workers might be
  in use so there may be nothing that can be immediately done.
- IIUC the excess workers (for a reduced GUC) are going to get freed naturally
  anyway over time as more transactions are completed so the pool size will
  reduce accordingly.

And given that the logic of this patch is simple, it would be easy to add this
at a later point if we really see a use case for this.

0002:

Since all the deadlock errors and other errors that caused by parallel streaming
will be logged and user can check this kind of ERROR and disable the parallel
streaming mode to resolve this. Besides, for this retry feature, It will
be hard to distinguish whether the ERROR is caused by parallel streaming, and we
might need to retry in serialize mode for all kinds of ERROR. So, it's not very
clear if automatic use serialize mode to retry in case of any ERROR in parallel
streaming is necessary or not. And we can also add this when we see a use case.

[1] https://www.postgresql.org/message-id/CAA4eK1LotEuPsteuJMNpixxTj6R4B8k93q-6ruRmDzCxKzMNpA%40mail.gmail.com

Best Regards,
Hou zj

Commits

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

  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.