Antwort: RE: Antwort: RE: server side sorting & paging? [Virus checked]

[denis.havlik@t-mobile.at]

>>There is a flow in this reasoning. Imagine a standard telephone book that
>>allows browsing trough complete set of data, sorted by surname (like a real
>>book does). Ther is an index on surname field, so server has no problems with
>>sorting & such.

>This is not a safe assumption. For example, OpenLDAP's indexing mechanism
>doesn't preserve ordering information, so sorting of indexed attributes
>doesn't come for free. The server uses hashes for indexing, to save on
>storage requirements. If indexing were also order-preserving, the space
>required (both in-RAM and on-disk) would be quite a bit higher.

I see. So this remains expensive operation even with index... Bad.

>I would say it's very rare that any client wants to browse the complete data.
>When was the last time you opened a paper telephone book and read it cover to
>cover, let alone reading an entire single page of entries?

Well.. Probably never. I do use google a lot though, and I could imagine other apps where zilions of results are returned, and I want to sort them by some criteria and give the user a page of results a time back.

Maybe such apps simply shouldn't use LDAP backends, end of the story.

In fact, I started thinking about this SSS for a completely different reason: I need to compare two LDAP dirs, both of them have user data, and each user has unique Personal number. It would be convenient to keep connection to both dirs open, and then pick up user data one by one sorted by ID - that way it's easy to see who's new and who's gone. 
I can do it in other ways, but this triggered the curiosity, and so... As I said, I'm in a learning mode. :-)

>>PS: Yes, I can see that things get REALLY funny as soon as we start working
>>with references, i.e. as soon as the data isn't all on a single server.
>That realization should tell you something...

Well, it tells me that some things should not be done with LDAP. Having this confirmed (or overrulled) by the folks who know LDAP better than I do is fine. 

What's confusing me is the fact that someone wrote the RFC 2891, and what's even more confusing me is that Kurt apparently worked on VLV some time ago. Maybe that looked like a good idea at first, but turned out to be a BadThing(TM) in the end?

regards
        Denis