RE: [bug fix] prepared transaction might be lost when max_prepared_transactions is zero on the subscriber

On Tuesday, December 23, 2025 12:21 PM Amit Kapila <amit.kapila16@gmail.com> wrote:
> 
> On Mon, Dec 22, 2025 at 2:31 PM Zhijie Hou (Fujitsu)
> <houzj.fnst@fujitsu.com> wrote:
> >
> > When reviewing some parallel apply related codes, I noticed a bug in
> > the parallel apply worker, similar to the issue discussed in this thread.
> >
> > The issue is that the logical replication parallel apply worker may
> > erroneously advance the origin progress during an error or
> > unsuccessful apply. This can lead to transaction loss, as these transactions
> will not be resent by the server.
> > Commit 3f28b2fc addressed a similar issue in both the apply worker and
> > table sync worker.
> >
> > The original fix involved registering a before_shmem_exit callback to
> > reset the origin information, preventing the worker from advancing it
> > during transaction abortion on shutdown. The attached patch registers
> > the same callback for the parallel apply worker, ensuring consistent
> behavior across all workers.
> >
> 
> Thanks for reporting the issue and patch.
> 
> +# Test the ability to re-apply a transaction when a parallel apply
> +worker fails # to prepare the transaction due to insufficient
> +max_prepared_transactions # setting.
> +$node_subscriber->append_conf('postgresql.conf',
> 
> How does the test ensure that error is raised by parallel apply worker? I see
> that in the previous test, we set 'debug_logical_replication_streaming =
> immediate', so that should help to invoke parallel apply worker. But is there a
> more direct way to ensure the same? Can we test for LOG like: "ERROR:
> logical replication parallel apply worker exited due to error"?

OK, I have added a general log test for "ERROR .. logical replication parallel
apply worker ..." to ensure that it's the parallel apply worker that failed to
apply the transaction.

And I also addressed the comments by Li Chao.

Here are the updated patches for all branches.

Best Regards,
Hou zj