Comment 1 for bug 1483496

I cannot figure out a way to test this. change_db_setting is a wrapper around alter database, but the results of that command only take effect for new connections. The current session doesn't know about the change. So there is no way to that I can see to begin a transaction, alter a database runtime setting, confirm that it was changed, and rollback the transaction.

Maybe someone else can figure it out.

This is a core postgresql feature though, setting the schema search path, and using alter database.
Josh