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From Emmanuel Lecharny <>
Subject Add perf issues
Date Sun, 09 May 2010 14:40:23 GMT

while doing some perf test on the Add operation, I'm getting blocked 
after having added around 3800 entries. After investigations, I found 
that some index are very expensive to update :
- the ObjectClass index quickly get saturated, and adding a new entry 
into it cost a hell of a time.
- same problem with the OneLevel index
- Same problem with the SubLevel index
- same problem with the RDN index
- from time to time, the UUID index takes 300 ms to synced, but that's 
random and it may be due to some page split
- all the other index behave perfectly well, assuming that they are not 
impacted, as we don't add any entry into them.

Ok, now, a blind guess is that those indexes, except the RDN index, will 
all contain a reference to the newy created entry, assuming I'm adding N 
entries whith a Dn:cn=test<N>,ou=system. They will be all in the same 
level (thus the pb with the OneLevel and SubLevel index), with all 
having the same OC (top and person) thus the problem with the OC index. 
I'm a bit more surprised by the RDN index problem, except if we consider 
that the ou=system RDN will point to all its children, then t makes 
sense that we have the same problem.

Basically, it seems that all the references are added in the same page 
which is deserialized and serialized for each addition, growing and 
growing. Do we have a size limit for a page after which it is moved to 
use a sub-tree ?

What's the strategy when we will have millions of entries under the 
'person' ObjectClass, or millions of entries in a flat directory? I 
thought this issue was fixed a while ago, and I'm a bit surprised hat it 
still present in the server, making it totally unusable. Or I'm missing 
a configuration parameter (like the max number of element in a page 
before a sub-tree is created).

Any help would be great !

Emmanuel L├ęcharny

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