How to migrate external procedure from Oracle Listener to Postgres Consider that I'm using C or java external procedure called from my Oracle 12.2 Listener (EXTPROC listener parameter).
That Oracle database will be migrated to Postgres.

My question is how to migrate the C or java external procedure?

Should I install C or java extension for Postgres, and then compile these procedures inside my Postgres database?
You can rewrite it as a normal C or PL/Java function in PostgreSQL.

If it is important for you to run the function in a separate process, give PL/Container a try.