This PR tries to track transaction state for each connection in a mark, indexed by the connection pid. But from my tests, all connections to datafusion-postgres & pgwire? seem to always be PID 0, and the Secret is also usually empty. Is the pgwire implementation incomplete?

I'm not tracking connections based on a unique ID, which is a hash of pid + secret_key + socket_address. So it's not more unique and should offer better connection state isolation.

@tonyalaribe Thank you! This should fix previous issue with transaction state. This was a mistake made in previous big PR.

But actually we don't need to have transaction management at this level, it's already bound with ClientInfo in pgwire: https://github.com/sunng87/pgwire/blob/master/src/api/mod.rs#L60

To update the transaction state, check this example: https://github.com/sunng87/pgwire/blob/master/examples/transaction.rs#L57

I can merge this but in my recent refactor, I will remove this transaction states from datafusion-postgres completely.

Thanks @sunng87. I think I'm happy with any solution you take. I agree that transaction management probably shouldn't be at that level.

Thanks for merging this, by the way. And thanks for this project.