The Design Specifications for MVCC Support in Ingres is available for
review at 'MVCC - Ingres Community Wiki'
(http://community.ingres.com/wiki/MVCC)

On Mon, Oct 26, 2009 at 5:05 PM, Ingres Forums
info-ingres at (no spam) kettleriverconsulting.com> wrote:


The Design Specifications for MVCC Support in Ingres is available for
review at 'MVCC - Ingres Community Wiki'
(http://community.ingres.com/wiki/MVCC)


It's nice to see such a fairly detailed specification. However, with very
few exceptions, the architecture of this is almost identical to Oracle's
MVCC design and implementation for acquiring a CR version of a block, which
is heavily patented for not only a single-server software architecture, but
also multi-server clustered architectures as well. For example, 4.1.9.1
lists CR buffers as being linked from the current version. While this is a
seemingly obvious implementation for all chained hash table-based DB buffer
management implementations, it is no different for Oracle. In Oracle, all
versions of a buffer similarly hash to the same bucket, and all are chained
to the current version. Likewise, the process listed in 4.1.9.4 is quite
close to Oracle's implementation in that they determine whether a CR version
needs to be created (by comparison of the SCN [similar to the comparison
against crib_low_lsn]), and perform iterative UNDO on that block
accordingly. While the high-level design is similar, in addition to the
coarse-grained block-level UNDO, Oracle can also follow a single tuple back
through multiple versions, which I don't see any conflict with here. Both
Oracle and SQL Server now support Postgres-like tuple-based MVCC for various
things, and both are using a fairly basic multi-version timestamp ordering
(MVTO) algorithm. Oracle's buffer manager still relies on UNDO-based MVRC,
but they use MVTO (rowscn) in a few other areas.

In my experience, UNDO-based MVRC is much more preferable to MVTO from both
a performance and manageability standpoint. It's just that Oracle has quite
a few patents on optimized MVRC designs whereas MVTO is so blatantly obvious
that it's an easy choice to make from a legality standpoint. Though, I'd be
happy to see Ingres get MVRC.

Regardless, I just wanted to make sure you guys are aware of the striking
similarities in the design, especially having referenced Oracle's own
documentation in the DDS. The only other system I know of which performed a
similar UNDO-to-reach-a-CR-version-of-the-block (albeit a little different
than Oracle's traditional method) is InnoDB, which of course is now Oracle's
IP as well. I'm not sure whether Oracle's patent policy has changed, but I
believe they have 3-6 fairly detailed patents for their MVCC implementation.

I am not a lawyer, but how on earth would one go about enforcing a
patent against an Open Source Community? Goodness knows how tough it¢s
been for the EU to bring Micro$oft to heel.

I suspect that Oracle would have nothing to gain from such a pursuit
[...].

Go MVCC Ingres!!!!!

Oracle has redo log groups and undo tablespaces whereas Ingres has
circular transaction log files

Quite different architectures you'll agree?


From a storage manager architecture, I agree that they are different to some
degree. Oracle's storage format was designed to act similarly to a file

I am not a lawyer, but how on earth would one go about enforcing a
patent against an Open Source Community? Goodness knows how tough it’s
been for the EU to bring Micro$oft to heel.

Oracle have much bigger fish to fry.

Go MVCC Ingres!!!!!

It’s been an awful long time coming - even if some reckon that it does
resemble Oracle's implementation! ;-P

Jonah, this is interesting stuff that deserves to be widely discussed,
and a newsgroup is a fine place to do it, but I doubt very many
people are going to take the time I just took to look up some of the
acronyms. Any chance you could post a more easily comprehended
version?

Would you know how EnterpriseDB protect themselves from Larry lawyers,
because EnterpriseDB's Advanced Server Oracle compatibility is a
blatant rip-off, If you ask me?!