[KPhotoAlbum] Optimization of index.xml

William Holland will at willholland.co.uk
Mon Sep 4 08:18:05 BST 2006


A while ago, I looked into synchronisation with mysql, and MySQL definitely 
supports synchronisation between two databases, so your best option is to 
look into the MySQL native Synchronisation, rather than writing a custom 
Kphotoalbum one. There were some issues with multiple updates to the same 
record in both databases, but this was 5 years ago, so it's probably 
improved.  Please don't ask me too many questions, as it's been nearly 4 
years since I last used mysql in anger... (the joys of real work taking over)


I suspect PostgreSQL has something similar.

Good luck


On Monday 04 Sep 2006 06:51, Shawn Willden wrote:
> On Tuesday 29 August 2006 08:13, Tuomas Suutari wrote:
> > Anyway MySQL and PostgreSQL are also supported by the SQL backend.
> Awesome!  This is truly excellent, and I'm really excited to be able for
> both my wife and I to be able to work with images at the same time, safely.
> That said, do you have any ideas about how I can manage the scenario where
> multiple copies of the database are in use?  Here's what I'm thinking: 
> Most of the time, we work on our photo database from home.  In that
> environment, MySQL or PostgreSQL are perfect (and, in fact, I already have
> a MySQL server installed on the home file server).  However, I not
> infrequently search for and/or modify photos when I'm traveling, and I want
> to be able to do that, too.
> Have you thought any about this sort of multi-database scenario? 
> Obviously, it's easy enough for me to take a copy of the database with me
> when I leave home, whether MySQL (which is already running on my laptop),
> SQLite or even XML.  The issue is how to synchronize any changes that I
> might make back to the authoritative database on the file server when I get
> home (or when I get an Internet connection).
> Obviously, any workable synchronization mechanism would have to recognize
> conflicting changes and offer the user the opportunity to resolve them.
> One way to do it would be a three-way compare.  If when I copied the DB to
> my laptop I stored two copies, one for active use and the other for
> reference, then it would be a simple matter to write a tool that compared
> my active laptop database to my reference database and propagated any
> differences to the server database, provided the server's copy of that row
> was the same as the reference database.
> Another way to do it would be to add an "updated" timestamp to each row. 
> Then I could do the synchronization without needing the extra copy of the
> database, I'd just have to know the time at which I performed the copy from
> server to laptop.  In order to avoid clock synchronization problems, the
> 'timestamp' I refer to would probably be a version counter, rather than a
> real timestamp, but the effect is the same.
> A third way would be to store a journal in the laptop DB of all of the
> changes made, along with their previous values,  This journal could then
> be "executed" against the server -- but only where the previous value
> matched the server version.  Differences would constitute conflicts.
> Another variant of the journaling approach would be to have both servers
> journal all of the changes, and record on the laptop the server's journal
> pointer.
> I'm sure there are other approaches, and perhaps some simpler, and better,
> than what I've described.
> Has anyone put any thought into this?  I'd be willing to write a
> synchronization tool, but it would be good to discuss an appropriate
> approach first.
> Oh, and what's the current state of the SQL support?  Can I try it now?
> 	Shawn.
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