How to detect a Prepared Transaction inside a trigger

Question

I have a problem with existing database code (a trigger) that call a function trigger that use the NOTIFY command, which is not supported in the context of a prepared transaction .

My question is simple : from the function trigger, is there a way to detect that we are in the context of a prepared transaction ?

Thanks in advance.

Answer 1

There is no way to detect that the current transaction will be committed using prepared transactions and two-phase commit, because you haven't PREPARE d the transaction yet; the transaction has no idea it's going to be subjected to two-phase commit until after your trigger runs. PostgreSQL doesn't require that you BEGIN TRANSACTION FOR TWO PHASE COMMIT (imaginary syntax) or anything like that.

You can test for max_prepared_transactions > 0 in pg_settings to see if prepared transactions are enabled , but there's no way to know if 2PC will be used until it happens.