Re: Add tests for concurrent DML retry paths in logical replication apply

Hi,

On Tue, Apr 28, 2026 at 12:47 AM Hayato Kuroda (Fujitsu)
<kuroda(dot)hayato(at)fujitsu(dot)com> wrote:
>
> > While reading the logical replication apply code in execReplication.c, I noticed
> > that the retry paths in RelationFindReplTupleByIndex and RelationFindReplTupleSeq
> > for concurrent updates and deletes have no test coverage [1]. Specifically,
> > when the same tuple is being updated/deleted on the publisher and subscriber at
> > the same time, the dirty snapshot finds the tuple being modified by another
> > transaction, the apply worker waits and retries the index/sequential scan.
>
> Good catch.
>
> > The attached patch adds an injection point before table_tuple_lock and a TAP test
> > exercising these retry paths, hitting both TM_Updated and TM_Deleted.
>
> I read the code briefly. Here are questions:

Thank you for reviewing!

> 1.
> The test looks like to add the test for retry acquiring the lock. But there is
> another retry path, which waits till xwait finishes. Do you have a reason to
> skip testing?

There are two retry paths, and I added TAP tests covering both. The
XactLockTableWait path is tested by holding an in-progress transaction
on the subscriber, which naturally blocks the apply worker until the
transaction finishes, then it retries the scan. The table_tuple_lock
retry path (TM_Updated / TM_Deleted) is tested using an injection
point that pauses the worker between finding and locking the tuple,
allowing concurrent DML to intervene.

> 2.
> Is it OK to use the same injection point name twice? I cannot find the existing
> case.

Good catch. I used separate injection points for each path.

Please find the attached v2 patch for further review. Thank you!

--
Bharath Rupireddy
Amazon Web Services: https://aws.amazon.com