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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: "kuroda.hayato@fujitsu.com" <kuroda.hayato@fujitsu.com>
Cc: Dilip Kumar <dilipbalaut@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, "shiy.fnst@fujitsu.com" <shiy.fnst@fujitsu.com>, Peter Smith <smithpb2250@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, "wangw.fnst@fujitsu.com" <wangw.fnst@fujitsu.com>, 'Amit Kapila' <amit.kapila16@gmail.com>
Date: 2022-10-06T14:21:10Z
Lists: pgsql-hackers 
On Thursday, October 6, 2022 9:00 PM Kuroda, Hayato/黒田 隼人 <kuroda.hayato@fujitsu.com> wrote:
> 
> Dear Hou,
> 
> > Thanks for the suggestion.
> >
> > I tried to add a WaitLatch, but it seems affect the performance
> > because the Latch might not be set when leader send some message to
> > parallel apply worker which means it will wait until timeout.
> 
> Yes, currently it leader does not notify anything.
> To handle that leader must set a latch in parallel_apply_send_data().
> It can be done if leader accesses to winfo->shared-> logicalrep_worker_slot_no,
> and sets a latch for LogicalRepCtxStruct->worker[slot_no].

Thanks for the suggestion. I think we could do that, but I feel it's not great
to set latch frequently. Besides, to access the LogicalRepCtxStruct->worker[]
we would need to hold a lock which might also bring some overhead.

Best regards,
Hou zj

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.