From: gabriele renzi <surrender_it@...1.vip.lng.yahoo.com>
Date: 2003-04-26T07:44:36+09:00
Subject: Re: Persistant data

il Sat, 26 Apr 2003 05:43:03 +0900, Matt Lawrence
<matt@black-bart.net> ha scritto::

>Ok, I've been looking at Marshal, PStore, Madelaine and mnemonic.  None of 
>them seem to provide the simple and transparent mechanism that I'm looking 
>for.
>
>I'd like to be able to do something like:
>
>	arr = PersistantArray.use("<filename>")
>	hash = PersistentHash.use("<filename>")
>
>Where <filename> is the name of the file to read and write data from and 
>the resulting object has all of the methods of Array or Hash and all 
>changes to the Array of Hash are automatically stored.  

# this could be completely wrong

I suppose that this is a work for persistence/prevalence layers, but I
don't think thay would actually save *each* change.

But it seem to me that working this way you'll have too many atomic
writings, and you'll loose in performance.

The Madeleine/prevayler approach  should be to save the state of the
application space with predefined time slices, while the persistence
layer approach should be about using save/retrieve methods, so you'll
just have to add a obj.save the way you'll use  Marshal(obj,io).

Possibly this performance/fault_tolerance problem is the same of the
sync/async writing in filesystems, and a middle-way approach a-la
Madeleine could be , imho, a good thing