From: Clifford Heath <no@...>
Date: 2008-09-28T18:54:18+09:00
Subject: Re: How to make Ruby _THE_ scripting language of choice, fold in SQLite

David Masover wrote:
> On Saturday 27 September 2008 20:34:32 Clifford Heath wrote:
>> David Masover wrote:
>>> Again, it's difficult to argue against this when you haven't told me which 
>>> ones aren't supported, and why.
>> DVCS exists because isolation isn't needed, since tools like patch
>> can often resolve conflicts and when they can't, a human can.
> 
> DVCS does, in fact, provide isolation (most checkouts are not public until 
> pushed to a public server).

That's not the definition of isolation. Isolation means that
two transactions that update the same piece of data will only
ever do so in a way that guarantees that the resultant state
*of the whole store* is valid, assuming that the two transactions
were valid when run independently. DVCS cannot do this, and most
importantly, do not even attempt to, though it's remarkably
effective at getting close most of the time.

Go check Wikipedia or anywhere else to verify this definition
before trying to create your own personal definition.

> "Experience at Amazon has shown that data stores that provide ACID guarantees 
> tend to have poor availability. This has been widely acknowledged by both the 
> industry and academia."

This doesn't bear on the ACID properties, but for the record, many
DBMSs sustain high transaction loads with astonishing availability.
Consider for example the availability of most major stock exchanges,
which run transaction loads in the many hundreds per second, every
trading day of the year, with almost no lack of availability. Many
other databases run high loads 24x7 for years without being restarted.
That's the sort of market where Tandem made their cash.

There's no chance in a million years that Amazon will ever achieve
the same availability measures, and their claim is either radically
out of context or just plain lies.

Clifford Heath.