> Yes, that is a good description. And old version is only required in the following
> two cases:
>
> 1. the txn that modified this tuple is still open (reader in default committed read)
> 2. reader is in serializable transaction isolation and has earlier xtid
>
> Seems overwrite smgr has mainly advantages in terms of speed for operations
> other than rollback.
... And rollback is required for < 5% transactions ...
Vadim