A lightweight connection pooler, that also has special features to
function as a pooler for PL/Proxy 2.
https://developer.skype.com/SkypeGarage/DbProjects/PgBouncer
Its features are:
* Special 'statement pooling' mode, where server connection is released
back to pool after each statement. Long transactions are disallowed
in this mode. It is needed for PL/Proxy 2.
* Low overhead, low resource usage.
* Easy to administer. Most settings are online reconfigurable.
Pooler can be upgraded without dropping connections, it can
pass sockets over to new process.
