Horton
Menu

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

Amit Kapila <amit.kapila16@gmail.com>

View thread
From: Amit Kapila <amit.kapila16@gmail.com>
To: Peter Smith <smithpb2250@gmail.com>
Cc: "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>, Masahiko Sawada <sawada.mshk@gmail.com>, "wangw.fnst@fujitsu.com" <wangw.fnst@fujitsu.com>, Dilip Kumar <dilipbalaut@gmail.com>, "shiy.fnst@fujitsu.com" <shiy.fnst@fujitsu.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2022-11-09T12:24:16Z
Lists: pgsql-hackers 
On Mon, Nov 7, 2022 at 1:46 PM Peter Smith <smithpb2250@gmail.com> wrote:
>
> Here are my review comments for v42-0001
...
...
>
> 8.
>
> + /*
> + * Resend the pending message to parallel apply worker to cleanup the
> + * queue. Note that parallel apply worker will just ignore this message
> + * as it has already handled this message while applying spooled
> + * messages.
> + */
> + result = shm_mq_send(winfo->mq_handle, strlen(winfo->pending_msg),
> + winfo->pending_msg, false, true);
>
> If I understand this logic it seems a bit hacky. From the comment, it
> seems you are resending a message that you know/expect to be ignored
> simply to make it disappear. (??). Isn't there some other way to clear
> the pending message without requiring a bogus send?
>

IIUC, this handling is required for the case when we are not able to
send a message to parallel apply worker and switch to serialize mode
(write remaining data to file). Basically, it is possible that the
message is only partially sent and there is no way clean the queue. I
feel we can directly free the worker in this case even if there is a
space in the worker pool. The other idea could be that we detach from
shm_mq and then invent a way to re-attach it after we try to reuse the
same worker.

-- 
With Regards,
Amit Kapila.

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.