The Directory Server now automatically generates an Index Summary Statistics Table, which can be used to determine the optimal configuration for your system's indexes. This table is only generated when the rebuild-index tool is run in offline mode. The table is generated after any LDIF import or an index rebuild, and is written to system out and to logs/tools/rebuild-index-summary.txt. The table lists the current index entry limit (set by the index-entry-limit property on the local DB configuration), the number of keys whose entry count exceeds this limit if any, and the maximum entry count for any key in the index. The table then displays a histogram of the number of keys whose entry falls within a range of values. An example of the Index Summary Statistics table is show below for the sn.equality and the sn.substring indexes.

The following figure shows that there are seven substrings whose entry counts exceed the index-entry-limit of 4000. Six of the substrings are in the 10000-99999 range with the maximum entry count being 13419. By deduction, one more substring must be present in the 1000-9999 range that exceeds the index-entry-limit of 4000. These substrings could be expensive for search operations.