request for database identifier in the startup packet

The JDBC driver is currently keeping a per connection cache of types in the driver. We are seeing cases where the number of columns is quite high. In one case Prevent fetchFieldMetaData() from being run when unnecessary. · Issue #3241 · pgjdbc/pgjdbc (github.com) 2.6 Million columns.

If we knew that we were connecting to the same database we could use a single cache across connections.

I think we would require a server/database identifier in the startup message.