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

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Peter Smith <smithpb2250@gmail.com>
Cc: "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>, "wangw.fnst@fujitsu.com" <wangw.fnst@fujitsu.com>, Dilip Kumar <dilipbalaut@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, "shiy.fnst@fujitsu.com" <shiy.fnst@fujitsu.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2022-10-24T11:58:43Z
Lists: pgsql-hackers 
On Mon, Oct 24, 2022 at 11:41 AM Peter Smith <smithpb2250@gmail.com> wrote:
>
> Here are my review comments for v40-0001.
>
> ======
>
> src/backend/replication/logical/worker.c
>
>
> 1. should_apply_changes_for_rel
>
> + else if (am_parallel_apply_worker())
> + {
> + if (rel->state != SUBREL_STATE_READY)
> + ereport(ERROR,
> + (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
> + errmsg("logical replication parallel apply worker for subscription
> \"%s\" will stop",
> + MySubscription->name),
> + errdetail("Cannot handle streamed replication transaction using parallel "
> +    "apply workers until all tables are synchronized.")));
>
> 1a.
> "transaction" -> "transactions"
>
> 1b.
> "are synchronized" -> "have been synchronized."
>
> e.g. "Cannot handle streamed replication transactions using parallel
> apply workers until all tables have been synchronized."
>
> ~~~
>
> 2. maybe_reread_subscription
>
> + if (am_parallel_apply_worker())
> + ereport(LOG,
> + (errmsg("logical replication parallel apply worker for subscription
> \"%s\" will "
> + "stop because the subscription was removed",
> + MySubscription->name)));
> + else
> + ereport(LOG,
> + (errmsg("logical replication apply worker for subscription \"%s\" will "
> + "stop because the subscription was removed",
> + MySubscription->name)));
>
> Maybe there is an easier way to code this instead of if/else and
> cut/paste message text:
>
> SUGGESTION
>
> ereport(LOG,
> (errmsg("logical replication %s for subscription \"%s\" will stop
> because the subscription was removed",
> am_parallel_apply_worker() ? "parallel apply worker" : "apply worker",
> MySubscription->name)));
> ~~~
>

If we want to go this way then it may be better to record the
appropriate string beforehand and use that here.

-- 
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.