> >> Impractical ? Oracle does it.
> >
> >Oracle has MVCC?
> 
> With restrictions, yes.

What restrictions? Rollback segments size?
Non-overwriting smgr can eat all disk space...

> You didn't know that?  Vadim did ...

Didn't I mention a few times that I was
inspired by Oracle? -:)

Vadim

Thu, 24 May 2001 10:00:31 -0700
"Mikheev, Vadim" <vmikheev@SECTORBASE.COM>
RE: Plans for solving the VACUUM problem 
"Mikheev, Vadim" wrote:
> 
> > >> Impractical ? Oracle does it.
> > >
> > >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 ? ;)

> > 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 ?

Could it possibly be a Postgres-inspired bolted-on hack 
needed for better concurrency ?


BTW, are you aware how Interbase does its MVCC - is it more 
like Oracle's way or like PostgreSQL's ?

----------------
Hannu

Fri, 25 May 2001 01:51:06 +0500
Hannu Krosing <hannu@tm.ee>
Re: Plans for solving the VACUUM problem
At 01:51 25/05/01 +0500, Hannu Krosing wrote:
>
>How does it do MVCC with an overwriting storage manager ?
>

I don't know about Oracle, but Dec/RDB also does overwriting and MVCC. It
does this by taking a snapshot of pages that are participating in both RW
and RO transactions (De/RDB has the options on SET TRANSACTION that specify
if the TX will do updates or not). It has the disadvantage that the
snapshot will grow quite large for bulk loads. Typically they are about
10-20% of DB size. Pages are freed from the snapshot as active TXs finish.

Note that the snapshots are separate from the journalling (WAL) and
rollback files.


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Fri, 25 May 2001 10:21:37 +1000
Philip Warner <pjw@rhyme.com.au>
Re: Plans for solving the VACUUM problem