Re: Plea for Server Side Sorting

[Howard Chu <hyc@symas.com>]

Christopher Hicks wrote:

> On Fri, 1 Apr 2005, Kurt D. Zeilenga wrote:
>
> > At 09:49 AM 4/1/2005, Armbrust, Daniel C. wrote:
> >
> > > Just making the point that sorting results isn't a limitation of 
> > > LDAP design in general
> >
> >
> > Your are arguably incorrect in this point. LDAP is designed
> > as an access protocol to a distributed directory service, and
> > that limits the kinds of capabilities the service can reasonably
> > be expected to offer.
>
>
> So the question boils down to: does it seem reasonable for a directory 
> service to sort results.  Its hard to imagine a corporate directory in 
> the real world that /isn't/ sorted, so for the computer equivalent to 
> be designed in a way that doesn't allow for sorting would seem to be 
> poorly modeled.
>
> In terms of considering LDAP as special-purpose database, there aren't 
> many databases that don't provide some sort facility.  SQL does.  The 
> UNIX command line does.  Mainframes and Minis with the many wacky 
> variations on ISAM do.
>
> In terms of IS system design and putting functionality in the most 
> logical place, we can have hundreds of different clients sort results 
> or have the server sort results.  It seems quite clear that having the 
> server sort results puts the code in the fewest places, which 
> naturally leads to fewer bugs, is better for programmer's mental 
> health everywhere, and so on.
>
> So in considering this from three different perspectives it seems not 
> only reasonable, but self-evident that LDAP should allow for sorting.

It is self-evident that LDAP clients should allow for sorting. Sorting 
is a function of the user interface, not of the underlying data store. 
The Unix command shells sort filenames as a matter of convention, but 
they are not stored in sorted order by the underlying filesystem. In 
terms of IS system design using a distributed data store, the most 
logical place for a function is where it is needed, and that may not 
coincide with where the data is stored.

Adding such a feature into the server violates one of the key principles 
of distributed system design - it cannot scale well as the number of 
clients increases. If you have hundreds of different clients making 
requests for sorting the server will quickly become overwhelmed and then 
none of the clients will get any service. Your request is as reasonable 
as asking that an NFS server return sorted directory listings to all of 
its filesystem clients. It doesn't happen. You may think it's happening 
because your command shell gives you a nicely sorted display, but that 
viewpoint only arises from a lack of understanding of the actual system 
architecture.

--
 -- Howard Chu
 Chief Architect, Symas Corp.       Director, Highland Sun
 http://www.symas.com               http://highlandsun.com/hyc
 Symas: Premier OpenSource Development and Support