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

Hayato Kuroda (Fujitsu) <kuroda.hayato@fujitsu.com>

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From: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>
To: 'Amit Kapila' <amit.kapila16@gmail.com>, "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>
Cc: Masahiko Sawada <sawada.mshk@gmail.com>, "wangw.fnst@fujitsu.com" <wangw.fnst@fujitsu.com>, Peter Smith <smithpb2250@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, "shiy.fnst@fujitsu.com" <shiy.fnst@fujitsu.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2022-11-30T11:35:58Z
Lists: pgsql-hackers 
Dear hackers,

> 1. I think testing the scenario where the shm_mq buffer is full
> between the leader and parallel apply worker would require a large
> amount of data and then also there is no guarantee. How about having a
> developer GUC [1] force_apply_serialize which allows us to serialize
> the changes and only after commit the parallel apply worker would be
> allowed to apply it?
> 
> I am not sure if we can reliably test the serialization of partial
> changes (like some changes have been already sent to parallel apply
> worker and then serialization happens) but at least we can test the
> serialization of complete xacts and their execution via parallel apply
> worker.

I agreed for adding the developer options, because the part that LA serialize
changes and PAs read and apply them might be complex. I have reported some
bugs around here.

One idea: A threshold(integer) can be introduced as the developer GUC.
LA skips to send data or jumps to serialization part to PA via shm_mq_send() when
it has sent more than (threshold) times. This may be able to test the partial-serialization case.
Default(-1) means no-op, and 0 means all changes must be serialized.

Best Regards,
Hayato Kuroda
FUJITSU LIMITED

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.