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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: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, Amit Kapila <amit.kapila16@gmail.com>
Cc: 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>, Masahiko Sawada <sawada.mshk@gmail.com>
Date: 2023-02-06T11:25:03Z
Lists: pgsql-hackers 
On Monday, February 6, 2023 6:34 PM Kuroda, Hayato <kuroda.hayato@fujitsu.com> wrote:
> > while reading the code, I noticed that in pa_send_data() we set wait
> > event to WAIT_EVENT_LOGICAL_PARALLEL_APPLY_STATE_CHANGE while
> sending
> > the message to the queue. Because this state is used in multiple
> > places, user might not be able to distinguish what they are waiting
> > for. So It seems we'd better to use WAIT_EVENT_MQ_SEND here which will
> > be eaier to distinguish and understand. Here is a tiny patch for that.
> 
> In LogicalParallelApplyLoop(), we introduced the new wait event
> WAIT_EVENT_LOGICAL_PARALLEL_APPLY_MAIN whereas it is practically waits a
> shared message queue and it seems to be same as WAIT_EVENT_MQ_RECEIVE.
> Do you have a policy to reuse the event instead of adding a new event?

I think PARALLEL_APPLY_MAIN waits for two kinds of event: 1) wait for new
message from the queue 2) wait for the partial file state to be set. So, I
think introducing a new general event for them is better and it is also
consistent with the WAIT_EVENT_LOGICAL_APPLY_MAIN which is used in the main
loop of leader apply worker(LogicalRepApplyLoop). But the event in
pg_send_data() is only for message send, so it seems fine to use
WAIT_EVENT_MQ_SEND, besides MQ_SEND is also unique in parallel apply worker and
user can distinglish without adding new event.

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.