The current version of the patch does not apply, so I could not test it. Here are some comments I have.
Pgbench is a simple benchmark tool by design, and I wonder if adding a multiconnect feature will cause pgbench to be used incorrectly. A real world use-case will be helpful for this thread. For the current patch, Should the report also cover per-database statistics (tps/latency/etc.) ? Regards, Sami Imseih Amazon Web Services