Can two-phase commit support LISTEN, UNLISTEN, and NOTIFY?

From: James Stuart <slim2k(at)privatejuris(dot)org>
To: pgsql-general(at)lists(dot)postgresql(dot)org
Subject: Can two-phase commit support LISTEN, UNLISTEN, and NOTIFY?
Date: 2023-09-15 17:55:38
Message-ID: f31290e4-7d3e-4784-252d-2f1863301522@privatejuris.org
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Can you please clarify, is lack of support for "LISTEN, UNLISTEN, and
NOTIFY" with two-phase commits an architecture limitation or is this
lacking implementation?  The NOTIFY happens after the transaction
commits and can't undo the transaction, so I can't think of any reason
why this could interfere with the two-phase commit.

https://www.postgresql.org/docs/current/sql-prepare-transaction.html

> "It is not currently allowed to PREPARE a transaction that has
executed any operations involving temporary tables or the session's
temporary namespace, created any cursors WITH HOLD, or executed LISTEN,
UNLISTEN, or NOTIFY. Those features are too tightly tied to the current
session to be useful in a transaction to be prepared."

I can't see a work-around even by writing to an event queue table.  The
event queue table can't be populated by either during a two-phase commit
so it would have to be polled negating the purpose of LISTEN / NOTIFY.

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