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From Emmanuel Lecharny <>
Subject [index review] System indexes
Date Thu, 14 May 2009 23:31:52 GMT
Ok, let's go deep into each system index now. We don't really care about 
user index right now.

First, we have to know that a system index can still be configured in 
the Server.xml file, because the user can set the index size. We need to 
clarify exactly what can be configured, what is the default and also 
discuss about what can be improved.

1) What can be configured

If we look at a standard server.xml file, here is what we typically find :

          <jdbmIndex attributeId="" 
          <jdbmIndex attributeId="objectClass" cacheSize="100"/>

Let's list the parameter we can work on :
- attributeId : the index's attribute ID
- cacheSize : the number of index entries to be cached
- numDupLimit : the threshold at which point duplicate keys use btree 
indirection to store the values. Default to 512
- wkDirPath : the working directory path used to store the index

2) Default values ?
The cacheSize is usually set to 100 elements. Some load tests are 
necessary to define the best possible value for this parameter. This is 
also the case for the numDupLimit parameter, which is set to 512 
elements, and atl never changed.

The working diretcory remains the same as the one associated with the 

3) What can be improved ?
It's obvious that having the OID instead of the name is not a good 
thing. We would rather have "apacheNdn" instead.

The parameter for the cache size should be dynamic (ie, it can be change 
while the server is running (at least increased)

cordialement, regards,
Emmanuel L├ęcharny

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