Don Baccus wrote:
>
> At 08:15 AM 5/24/01 +0900, Hiroshi Inoue wrote:
>
> >> Unless we want to abandon MVCC (which I don't), I think an overwriting
> >> smgr is impractical.
> >
> >Impractical ? Oracle does it.
>
> It's not easy, though ... the current PG scheme has the advantage of being
> relatively simple and probably more efficient than scanning logs like
> Oracle has to do (assuming your datafiles aren't thoroughly clogged with
> old dead tuples).
>
> Has anyone looked at InterBase for hints for space-reusing strategies?
>
> As I understand it, they have a tuple-versioning scheme similar to PG's.
>
> If nothing else, something might be learned as to the efficiency and
> effectiveness of one particular approach to solving the problem.
It may also be beneficial to study SapDB (which is IIRC a branch-off of
Adabas) although they claim at http://www.sapdb.org/ in features
section:
NOT supported features:
Collations
Result sets that are created within a stored procedure and
fetched outside. This feature is planned to be offered in one of the coming releases.
Meanwhile,use temporary tables. see Reference Manual: SAP DB 7.2 and 7.3 -> Data
definition -> CREATE TABLE statement: Owner of a table
Multi version concurrency for OLTP It is available with the object extension of SAPDB only.
Hot stand by This feature is planned to be offered in one of the coming
releases.
So MVCC seems to be a bolt-on feature there.
---------------------
Hannu
