Several levels of brutality when rotating connections:

Session pooling - Most polite method. When client connects, a server
connection will be assigned to it for the whole duration it stays
connected. When client disconnects, the server connection will be put
back into pool.

Transaction pooling - Server connection is assigned to client only
during a transaction. When PgBouncer notices that transaction is over,
the server will be put back into pool. This is a hack as it breaks
application expectations of backend connection. You can use it only
when application cooperates with such usage by not using features that
can break. See the table below for breaking features.

Statement pooling - Most aggressive method. This is transaction
pooling with a twist - multi-statement transactions are disallowed.
This is meant to enforce "autocommit" mode on client, mostly targeted
for PL/Proxy.

• Alexey Shabalin
• Grigory Ustinov
• Ivan Zakharyaschev
• Denis Medvedev
• Alexander V Openkin

• pgbouncer
• pgbouncer-debuginfo