Avoid crash after function syntax error in a replication worker.
If a syntax error occurred in a SQL-language or PL/pgSQL-language
CREATE FUNCTION or DO command executed in a logical replication worker,
we'd suffer a null pointer dereference or assertion failure. That
seems like a rather contrived case, but nonetheless worth fixing.
The cause is that function_parse_error_transpose assumes it must be
executing within the context of a Portal, but logical/worker.c
doesn't create a Portal since it's not running the standard executor.
We can just back off the hard Assert check and make it fail gracefully
if there's not an ActivePortal. (I have a feeling that the aggressive
check here was my fault originally, probably because I wasn't sure if
the case would always hold and wanted to find out. Well, now we know.)
The hazard seems to exist in all branches that have logical replication,
so back-patch to v10.
Maxim Orlov, Anton Melnikov, Masahiko Sawada, Tom Lane
Discussion: https://postgr.es/m/
b570c367-ba38-95f3-f62d-
5f59b9808226@inbox.ru
Discussion: https://postgr.es/m/
adf0452f-8c6b-7def-d35e-
ab516c80088e@inbox.ru