From: George Moschovitis <gm@...>
Date: 2004-10-08T23:29:45+09:00
Subject: Re: [ANN] ndb Object-Relational Mapper

Brian Candler wrote:
> On Fri, Oct 08, 2004 at 10:39:44PM +0900, George Moschovitis wrote:
> 
>>Have a look at the following link tha explains this technique:
>>
>>http://www.ibase.ru/devinfo/DBMSTrees/sqltrees.html
> 
> 
> This is a very cute data structure which I hadn't come across before.
> However, if I add a new subordinate to 'Bert' (say 'Bob'), don't I end up
> having to renumber almost the entire tree?

Yeap this is the tradeoff. Slower inserts give you faster (and constant 
time) reads. The tradeoff compared to your idea is generality.

The latest version of the web application framework we are using here at 
Navel further encapsulates this pattern to make it almost transparent. 
It is very usefull for fora messages, comments and more.

I 'll probably also add a Mixin for the 'materialized paths' method you 
described (this is the 'formal' name) in the next version of n/Db. 
Sometime in the next week, I hope.

best regards
George Moschovitis

ps: I would really like to have a look at your xpath->sql translator.


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