6.4. Using Indexes to Improve Database Performance
cn.db4contains all of the indexes for the common name attribute.
6.4.1. Overview of Directory Index Types
- Presence index — Lists entries that possess a particular attribute, such as
- Equality index — Lists entries that contain a specific attribute value, such as
- Approximate index — Allows approximate (or "sounds-like") searches. For example, an entry might contain the attribute value of
cn=Babs L. Jensen. An approximate search would return this value for searches against
NoteApproximate indexes require that names be written in English using ASCII characters.
- Substring index — Allows searches against substrings within entries. For example, a search for
cn=*dersonwould match common names containing this string (such as Bill Anderson, Norma Henderson, and Steve Sanderson).
- International index — Improves the performance of searches for information in international directories. Configure the index to apply a matching rule by associating a locale (internationalization OID) with the attribute being indexed.
- Browsing index or virtual list view (VLV) index — Improves the display performance of entries in the Directory Server Console. A browsing index can be created on any branch in the directory tree to improve the display performance.
6.4.2. Evaluating the Costs of Indexing
- Indexes increase the time it takes to modify entries.The more indexes being maintained, the longer it takes the directory service to update the database.
- Index files use disk space.The more attributes being indexed, the more files are created. If there are approximate and substring indexes for attributes that contain long strings, these files can grow rapidly.
- Index files use memory.To run more efficiently, the directory service places as many index files in memory as possible. Index files use memory out of the pool available depending upon the database cache size. A large number of index files requires a larger database cache.
- Index files take time to create.Although index files save time during searches, maintaining unnecessary indexes can waste time. Be certain to maintain only the files needed by the client applications using the directory service.