RE: BUG #16481: Stored Procedure Triggered by Logical Replication is Unable to use Notification Events

Hi Kyotaro Horiguchi, thanks for you helps.
We have a question about the bug. Why there isn't any solution in the HEAD?

This bug last since 10.4 version and I can't understand why it is not fixed in the HEAD yet.

BR.
Fabio Vianello.

-----Original Message-----
From: Kyotaro Horiguchi [mailto:horikyota(dot)ntt(at)gmail(dot)com]
Sent: lunedì 8 giugno 2020 10:28
To: Vianello Fabio <fabio(dot)vianello(at)salvagninigroup(dot)com>; pgsql-bugs(at)lists(dot)postgresql(dot)org; pgsql-hackers(at)lists(dot)postgresql(dot)org
Subject: Re: BUG #16481: Stored Procedure Triggered by Logical Replication is Unable to use Notification Events

Hello.

It seems to me a bug.

At Fri, 05 Jun 2020 11:05:14 +0000, PG Bug reporting form <noreply(at)postgresql(dot)org> wrote in
> The following bug has been logged on the website:
>
> Bug reference: 16481
> Logged by: Fabio Vianello
> Email address: fabio(dot)vianello(at)salvagninigroup(dot)com
> PostgreSQL version: 12.3
> Operating system: Windows 10
> Description:
>
> About the bug BUG #15293, on PostgreSQL version 10.4 and 11.2 as
> describe below, we found the same issue on the PostgreSQL version 12.3.

The HEAD behaves the same way.

> Is it a feature?
> Becasue in the documentation we didn't found any constraint that says
> that we can not use NOTIFY/LISTEN on logical replication tables.
>
> "When using logical replication a stored procedure executed on the
> replica is unable to use NOTIFY to send messages to other listeners.
> The stored procedure does execute as expected but the pg_notify()
> doesn't appear to have any effect. If an insert is run on the replica
> side the trigger executes the stored procedure as expected and the
> NOTIFY correctly notifies listeners.

The message is actually queued, but logical replication worker doesn't signal that to listener backends. If any ordinary session sent a message to the same listener after that, both messages would be shown at once.

That can be fixed by calling ProcessCompletedNotifies() in apply_handle_commit. The function has a code to write out notifications to connected clients but it doesn't nothing on logical replication workers.

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center
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