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From Emmanuel Lecharny <>
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 09:18:41 GMT
Howard Chu wrote:
> 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...
I now that theory != real life, but for a search which is not based on 
the DN, I can't see how a double lookup ( one for the entry + one for 
the DN) could be as fast as a simple one, assuming that you still need 
to provide the DN.

For searches based on DN, performances should be identical, as you will 
have to read the DN anyway..

So for search, theory says : storing the DN within the entry should be 
faster (if you each the cache), unless you have a limited memory size 
and have to hit the disk more. But even then, I'm not sure that the 
difference in performance would be noticable, unless you have hundred of 
millions entries and not a lot of memory.

Is my theory wrong ?

Now, what would be very interesting is to gather real life data about 
what people _really_ do on their servers, with stats :
- How many SearchRequest // Modify // Add // Delete // ModifyDN
- for SearchRequests, ratio between DN based searches // attribute based 

>> 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...
That would be a great pleasure ! I'm pretty sure that having an OpenLDAP 
admin plugin would be a big plus !

Thanks !

FYI, LdapConference won't occurs this year.

cordialement, regards,
Emmanuel L├ęcharny

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