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From "David Jordan" <davej...@bellsouth.net>
Subject RE: fetch-depth + recursion-depth
Date Mon, 19 Dec 2005 12:53:51 GMT

Allowing multiple levels of a tree structure to be pre-fetched would allow
more efficient traversal of the tree structure than simply iterating one
level at a time. The implementation could use relational vendor specific
features, I know Oracle supports such recursive traversals.

David Jordan
Object Identity, Inc.


-----Original Message-----
From: Marco Schulze [mailto:Marco@NightLabs.de] 
Sent: Monday, December 19, 2005 7:23 AM
To: jdo-dev@db.apache.org
Cc: jdo-experts-ext@sun.com
Subject: Re: fetch-depth + recursion-depth

Jörg von Frantzius wrote:
> After having thought about it for a while, I started to doubt whether 
> we really need a "recursion-depth" number  here. Can you think of a 
> case where you'd need any value greater than 1 here?
We have a case in which we need a "recursion-depth" greater than 1:

We use a tree of objects (all of the same class, self-referencing via a 
Collection), where the GUI loads this tree initially with 
recursion-depth=2 in order to immediately show the first level of the 
tree expanded and the second level ready - with already knowing whether 
an expand-icon needs to be visible or not. In other words: we load 
always one level more in the tree than is visible for avoiding the 
expand-icon to be visible even though there are no children.
> So I'd rather call this a boolean flag "recurse-class-cycles".
IMHO, the implementation work for a boolean flag is the same as for a 
number, so the flexibility of a count should be preferred.
> I can't see why the spec should be changed for this rather than 
> extended. Your requirement for a cycle-detection probably doesn't 
> invalidate existing requirements for an absolute fetch-depth.
With "changed" I meant "extended".


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