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From Howard Chu <...@symas.com>
Subject Re: [ApacheDS] [JDBM Partition] Why it's a BAD idea to store the Entry + DN in the master table
Date Thu, 07 Aug 2008 08:00:49 GMT
Emmanuel Lecharny wrote:
> Howard Chu wrote:
>> Emmanuel Lecharny wrote:
>>> Alex Karasulu wrote:
>>>> Hi all,
>>>>
>>> Hi Alex,
>>>> The ServerEntry stores the DN of the entry.  I think this is good
>>>> for better
>>>> code organization.  However, storing the entry together with it's DN
>>>> into
>>>> the master table is a very bad idea.  The DN should instead be
>>>> managed in
>>>> the NDN and DN indices.
>>>>
>>> I think you are wrong. Storing the DN within the entyr is a very good
>>> idea (tm) :)
>> For what it's worth, in my experience Alex is right. OpenLDAP's
>> back-hdb can do subtree renames in O(1) time. It's the only LDAP
>> implementation in the world that can do this, and it's partly because
>> we don't store the DNs with the rest of the entry data. back-hdb is
>> also the fastest at searches too, and that's just a matter of
>> balancing cache demands...
> Apache DS 1.0 was also able to do ModifyDN in O(1) :)
>
> All the profiling sessions I did last year shown that, for ADS, storing
> DN outside the entry was costing more than storing them within the
> entry. We will do more tests :)
>
> The good thing is that we can move back to have the DN stored outside
> the DN easily, the hard part was to define the Entry class and use it
> all over the server !
>
> Let's evaluate both solution, and pick the one which is the fastest !
> (and whoever is right or wrong does not matter, as soon as we have a
> faster server :)

In our case, back-bdb and back-hdb basically have identical search 
performance. So there's really no downside to supporting fast ModifyDN in 
back-hdb, and we've been intending to phase out back-bdb...

> Thanks Howard, as usual, your insights are always good to have ! (when
> you will hate Java less, let us know, we have a warm and comfortable
> place for you at Directory :)

Heh heh... Still enjoying the work you guys have done with DirectoryStudio. 
You may find me writing java code there sooner or later...

-- 
   -- Howard Chu
   CTO, Symas Corp.           http://www.symas.com
   Director, Highland Sun     http://highlandsun.com/hyc/
   Chief Architect, OpenLDAP  http://www.openldap.org/project/

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