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From "Ersin Er" <ersin...@gmail.com>
Subject Re: ApacheDS partition implementation based on Relational Model
Date Sun, 12 Nov 2006 07:27:26 GMT
On 11/12/06, David Boreham <david@bozemanpass.com> wrote:
>
> >> > If we go to RDBMS, this would be the worst approach. It is suppose
> >> to be
> >> > a relationnal model, not an hierarchical model mapped on a relationnal
> >> > model. Performance will be awfull
> >
> I missed a few iterations in this thread (been busy with the day job),
> but some late thoughts:
>
> 1. Have you looked at what's inside a RDBMS engine ?
> B-trees and query processing that's much the same as
> the average directory server. So mapping the DS's b-tree
> relations to tables (which are themselves implemented as
> b-trees) is not imho an inefficient approach.

I am perfectly aware of these. BTW, we are not mapping DIT to RDBMS'
B-Trees. We are mapping DIT to Tables and they map to B-Trees. So of
course there will be an overhead.

> 2. the dit hierarchy is  really a non-problem for RDBMS
> mapping -- after all DS'es that use b-tree storage managers
> directly already have the same identical problem to solve.
> the average DIT is not very bushy nor deep anyway.

I think hierarchy is a serious problem for RDBMS. You cannot select
all subordinate entries of an entry in a single search. This requires
a recursive search. Oracle has support for this
(http://www.adp-gmbh.ch/ora/sql/connect_by.html) but non-standard.

> 3. If you are concerned about performance, don't use
> a RDBMS. The approach already chosen for Apache DS
> is the most performant (possibly needs some work, but
> it's the right way to go for performance).
>
> 4. Attempting to 'really use' the relational data model for
> directory entries takes us back to the previously mentioned
> relational mapping science project. (Customer already
> has a bunch of tables in Oracle, and we need to refect
> those via LDAP) Certainly an interesting
> field to study, but there's no obvious good way to solve
> this problem that I know of. Virtual Directory and sync
> (meta) type solutions have addressed this area for
> years with a fair degree of success.

We are just trying to see what it costs. So we can say do not use
RDBMS but ApacheDS when it really fits your needs :-)

Thanks.

-- 
Ersin

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