From: David Masover <ninja@...>
Date: 2008-09-27T09:09:35+09:00
Subject: Re: How to make Ruby _THE_ scripting language of choice, fold in SQLite

On Friday 26 September 2008 07:34:41 Clifford Heath wrote:
> David Masover wrote:
> >> Nevertheless, though this method can solve the (D)urability problem of
> >> ACID, it offers no solution to A, C, or I, so is still not transactional.

> This ability to perform single operations with ACID semantics is
> assumed - because without it we can't do any more - and hence
> isn't interesting. If the chunk you choose is a whole file, it
> still isn't interesting, because it's still all or nothing on a
> single object. No-one rewrites an entire database to save one
> record.

No, the point here is that a file is not a whole database, but is rather one 
record. In this way, Maildir is a step up from mbox, in that maildir allows 
single emails to be created, destroyed, or moved, without rewriting the 
entire database.

> The interesting cases arise when you must coordinate updates to
> more than one such object.

That invalidates the filesystem example, and (to some extent) S3, but not 
Dynamo or DVCS, as I understand it.

> The examples you gave do not provide a use case where all 4 ACID
> properties are supported in such multi-atom situations - they only
> support or require some subset.

Again, it's difficult to argue against this when you haven't told me which 
ones aren't supported, and why.

I'll go read the Dynamo paper again, then...