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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: 2022-09-13T10:25:51Z
Lists: pgsql-hackers 
On Fri, Sep 9, 2022 at 12:32 PM Peter Smith <smithpb2250@gmail.com> wrote:
>
> 29. src/backend/replication/logical/worker.c - TransactionApplyAction
>
> /*
>  * What action to take for the transaction.
>  *
>  * TA_APPLY_IN_LEADER_WORKER means that we are in the leader apply worker and
>  * changes of the transaction are applied directly in the worker.
>  *
>  * TA_SERIALIZE_TO_FILE means that we are in leader apply worker and changes
>  * are written to temporary files and then applied when the final commit
>  * arrives.
>  *
>  * TA_APPLY_IN_PARALLEL_WORKER means that we are in the parallel apply worker
>  * and changes of the transaction are applied directly in the worker.
>  *
>  * TA_SEND_TO_PARALLEL_WORKER means that we are in the leader apply worker and
>  * need to send the changes to the parallel apply worker.
>  */
> typedef enum
> {
> /* The action for non-streaming transactions. */
> TA_APPLY_IN_LEADER_WORKER,
>
> /* Actions for streaming transactions. */
> TA_SERIALIZE_TO_FILE,
> TA_APPLY_IN_PARALLEL_WORKER,
> TA_SEND_TO_PARALLEL_WORKER
> } TransactionApplyAction;
>
> ~
>
> 29a.
> I think if you change all those enum names slightly (e.g. like below)
> then they can be more self-explanatory:
>
> TA_NOT_STREAMING_LEADER_APPLY
> TA_STREAMING_LEADER_SERIALIZE
> TA_STREAMING_LEADER_SEND_TO_PARALLEL
> TA_STREAMING_PARALLEL_APPLY
>
> ~
>

I also think we can improve naming but adding streaming in the names
makes them slightly difficult to read. As you have suggested, it will
be better to add comments for streaming and non-streaming cases. How
about naming them as below:

typedef enum
{
TRANS_LEADER_APPLY
TRANS_LEADER_SERIALIZE
TRANS_LEADER_SEND_TO_PARALLEL
TRANS_PARALLEL_APPLY
} TransApplyAction;

-- 
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.