The virtualxid lock is special. It’s a exclusive lock on the transaction’s own virtual transaction ID that every transaction always holds. No other transaction can ever acquire it while the transaction is running.
The purpose of this is to allow one transaction to wait until another transaction commits or rolls back using PostgreSQL’s locking mechanism, and it’s used internally.
I noticed that pg_locks has an addition row for every transaction that is created with a locktype "virtualxid". Tried to search it online but I didnt find an explanation for this behavior. Does anyone can explain why it happens ?