Vadim Mikheev wrote:
>
> > 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 ...
This obviously depends on application.
I know people who rollback most of their transactions (actually they use
it to
emulate temp tables when reporting).
OTOH it is possible to do without rolling back at all as MySQL folks
have
shown us ;)
Also, IIRC, pgbench does no rollbacks. I think that we have no
performance test that does.
-----------------
Hannu