Sun Directory Server Enterprise Edition 7.0 Reference

Substring Index

Substring indexes are used for searches on three-character groups, for example, sn=*abc*. The three-character groups are stored in the index. Substring indexes cannot be applied to binary attributes such as photos. The following figure shows a substring index for the SN attribute.

Figure 9–3 Substring Index for the SN Attribute

Illustration of a substring index for the SN attribute.

The Directory Server search algorithm includes optimizations for the following searches, however, these searches are more likely to reach the index list threshold:

Directory Server builds an index of substrings according to its own built-in rules. Substring indexes cannot be configured by the system administrator.

When Directory Server receives a request to update an entry that has an attribute indexed for substrings, it must do the following tasks before performing the update and acknowledging the update to the client:

Maintaining substring indexes is relatively costly; the cost is a function of the length of the string indexed. To minimize cost, avoid unnecessary substring indexes, especially for attributes that have potentially long string values such as a description.