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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>, "wangw.fnst@fujitsu.com" <wangw.fnst@fujitsu.com>
Cc: Amit Kapila <amit.kapila16@gmail.com>, 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>
Date: 2022-09-22T08:57:24Z
Lists: pgsql-hackers 
On Thursday, September 22, 2022 4:08 PM Kuroda, Hayato/黒田 隼人 <kuroda.hayato@fujitsu.com> wrote:
> 
> Thanks for updating the patch! Followings are comments for v33-0001.

Thanks for the comments.

> 04. HandleParallelApplyMessages()
> 
> ```
> +               if (winfo->error_mq_handle == NULL)
> +                       continue;
> ```
> 
> a.
> I was not sure when the cell should be cleaned. Currently we clean up
> ParallelApplyWorkersList() only in the parallel_apply_start_worker(), but we
> have chances to remove such a cell like HandleParallelApplyMessages() or
> HandleParallelApplyMessage(). How do you think?

HandleParallelApplyxx functions are signal callback functions which I think
are unsafe to cleanup the list cells that may be in use before entering
these signal callback functions.


> 
> 05. parallel_apply_setup_worker()
> 
> ``
> +       if (launched)
> +       {
> +               ParallelApplyWorkersList = lappend(ParallelApplyWorkersList,
> winfo);
> +       }
> ```
> 
> {} should be removed.

I think this style is fine and this was also suggested to be consistent with the
else{} part.


> 
> 06. parallel_apply_wait_for_xact_finish()
> 
> ```
> +               /* If any workers have died, we have failed. */
> ```
> 
> This function checked only about a parallel apply worker, so the comment
> should be "if worker has..."?

The comments seem clear to me as it's a general comment.

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.