I should have clarified, I meant at the protocol level. It's basically a state machine, and I want a "break" to reset the state machine. This would flush remaining query results, close named prepared statements, rollback any in-process transactions, and put the state back at ready-for-query. In the meantime, those with connections pools (this lib, my client-side lib, etc) have to keep this info (often except prepared statements which is the caller's responsibility to close).
I am talking about the protocol, not a query. What if the state of the connection is not even at ready-for-query state, how do I issue a query? There is no DISCARD ALL in the protocol [0]. You might have only read 3 rows and still have a thousand to flush, or you might have sent a Parse and are awaiting a ParseComplete. This is the type of thing that a Postgres connection pooler has to keep track of. Here's some of their code: https://github.com/yandex/odyssey/blob/master/sources/reset.... (note how it has to get back to ready-for-query state before rolling back).