In Postgres - when transaction IDs wraparound what are their numbers? In Postgres 11, when transaction IDs pass the 4 billion wraparound mark, assuming that the database is properly autovacuumed, what will be the next txid returned by txid_current()? 

Will the returned transaction IDs start again from 1 or will they continue to have IDs greater than 4 billion and the txid_current() will return numbers greater than 4 billion.

The documentation says "... these functions export a 64-bit format that is extended with an “epoch” counter so it will not wrap around during the life of an installation."  So my understanding is that txid_current() returns bigint and the the returned txid will not start from zero. postgresql.org/docs/11/functions-info.html
The docs state that


  the XID counter wraps around to zero