> > > >Oracle has MVCC?
> > >
> > > With restrictions, yes.
> >
> > What restrictions? Rollback segments size?
> > Non-overwriting smgr can eat all disk space...
>
> Is'nt the same true for an overwriting smgr ? ;)
Removing dead records from rollback segments should
be faster than from datafiles.
> > > You didn't know that? Vadim did ...
> >
> > Didn't I mention a few times that I was
> > inspired by Oracle? -:)
>
> How does it do MVCC with an overwriting storage manager ?
1. System Change Number (SCN) is used: system increments it on each transaction commit.
2. When scan meets data block with SCN > SCN as it was when query/transaction started, old block image is restored
usingrollback segments.
> Could it possibly be a Postgres-inspired bolted-on hack
> needed for better concurrency ?
-:)) Oracle has MVCC for years, probably from the beginning
and for sure before Postgres.
> BTW, are you aware how Interbase does its MVCC - is it more
> like Oracle's way or like PostgreSQL's ?
Like ours.
Vadim