RE: comparison with cloudscape?

All,

I have never developed my own database (as Toby has done) but I have used
Mckoi, PointBase, Cloudscape/Derby, and Oracle, aod I may be able to to
provide a little more detail.

Let me say first that Mckoi is a very high quality multi-versioning database
system.  It works well and is very popular.

Mckoi support (only) the serializable transaction isolation level.  The
other databases listed above also support serializable, but it is
implemented differently.

In Mckoi there is no application-level locking.  If user A and user B are
performing transactions that conflict with each other, the first one to
commit their transaction "wins".  His changes are made permanent.  The other
user's transaction will fail when he commits.

In other databases, this would be prevented with locking.  For example, if
user A modifies a particular record, then an attempt by user B to modify the
record would fail when he attempted to execute the UPDATE statement.  User
A's transaction would have the record locked.

Also, before using serializable realize that any changes made by user A will
not be visible to user B, even after user A commits, until the user B starts
a new transaction by committing or rolling back.  This is required by the
serializable transaction isolation level.

The default isolation level for PointBase, Cloudscape/Derby, and Oracle is
read committed.  With this transaction isolation level other uses will see
committed changes, however, implementation of this transaction isolation
level requires locking.

Toby has done a great job implementing Mckoi, and if serializable will work
for you, I would recommend using it.  Please let me know if anything above
is inaccurate.

Bob


-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Tobias
Downer
Sent: Thursday, December 02, 2004 7:57 PM
To: [email protected]
Subject: Re: comparison with cloudscape?


David,

I don't have great knowledge of Cloudscape/Derby so I'll leave it up to 
anyone who is more knowledgeable to correct me, but I believe the main 
difference is that Mckoi is a strictly versioning database system 
whereas Derby uses a DB2 style locking transaction model.

Derby will be more comfortable with developers who are familiar with DB2 
and Mckoi will be more comfortable with Oracle and PostgreSQL developers.

Toby.

David Coldrick wrote:
> Or whatever they're calling it now :-). Becomes a reasonable question
> now it's been open-sourced.
> 
> Tobias, you could probably answer this better than anyone: what do you
> feel are the differences between mckoidb and cloudscape?
> 
> Regards,
> David


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