I'm well aware of how the extended protocol works, but it seems odd for a 30% increase in processing time to be the result exclusively of processing 5 messages instead of just 1 - it doesn't seem like that big a deal (although I may be mistaken). I was imagining that there's something more fundamental in how the protocol or PostgreSQL state is managed internally, that would be responsible for the slowdown.
Hi, have you tried to use a profiler to identify the _cause_ of the difference in performance?