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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: "kuroda.hayato@fujitsu.com" <kuroda.hayato@fujitsu.com>
Cc: "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>, "wangw.fnst@fujitsu.com" <wangw.fnst@fujitsu.com>, Peter Smith <smithpb2250@gmail.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: 2022-09-13T10:49:59Z
Lists: pgsql-hackers 
On Mon, Sep 12, 2022 at 4:27 PM kuroda.hayato@fujitsu.com
<kuroda.hayato@fujitsu.com> wrote:
>
> Dear Hou-san,
>
> Thank you for updating the patch! Followings are comments for v28-0001.
> I will dig your patch more, but I send partially to keep the activity of the thread.
>
> ===
> For applyparallelworker.c
>
> 01. filename
> The word-ordering of filename seems not good
> because you defined the new worker as "parallel apply worker".
>

I think in the future we may have more files for apply work (like
applyddl.c for DDL apply work), so it seems okay to name all apply
related files in a similar way.

>
> ===
> For worker.c
>
> 07. general
>
> In many lines if-else statement is used for apply_action, but I think they should rewrite as switch-case statement.
>

Sounds reasonable to me.

> 08. global variable
>
> ```
> -static bool in_streamed_transaction = false;
> +bool in_streamed_transaction = false;
> ```
>
> a.
>
> It seems that in_streamed_transaction is used only in the worker.c, so we can change to stati variable.
>

Yeah, I don't know why it has been changed in the first place.

> b.
>
> That flag is set only when an apply worker spill the transaction to the disk.
> How about "in_streamed_transaction" -> "in_spilled_transaction"?
>

Isn't this an existing variable? If so, it doesn't seem like a good
idea to change the name unless we are changing its meaning.

-- 
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.