How Directory Server Performs Searches by Using Cache

In Figure 5–2, individual lines represent threads that access different levels of memory. Broken lines represent probable bottlenecks to minimize through effective tuning of Directory Server.

Figure 5–2 How Directory Server Performs Searches

The following sections describe how Directory Server performs searches by using the cache. By processing subtree searches as described in the following sections, Directory Server returns results without loading the whole set of results into memory.

How Directory Server Performs Base Searches

Base searches specify a base DN and are the simplest type of searches for Directory Server to manage. Directory Server processes base searches in the following stages.

1. Directory Server attempts to retrieve the entry from the entry cache.

   If the entry is found in the entry cache, Directory Server checks whether the candidate entry matches the filter provided for the search.

   If the entry matches the filter provided for the search, Directory Server returns the formatted, cached entry to the client application.

2. Directory Server attempts to retrieve the entry from the database cache.

   If the entry is found in the database cache, Directory Server copies the entry to the entry cache for the suffix. Directory Server proceeds as if the entry had been found in the entry cache.

3. Directory Server attempts to retrieve the entry from the database itself.

   If the entry is found in the database, Directory Server copies the entry to the database cache . Directory Server proceeds as if the entry had been found in the database cache.

How Directory Server Performs Subtree and One-Level Searches

Searches on a subtree or a level of a tree involve additional processing to handle multiple entries. Directory Server processes subtree searches and one-level search in the following stages.

1. Directory Server attempts to define a set of candidate entries that match the filter from indexes in the database cache.

   If no appropriate index is present, the set of candidate entries must be found directly in the database itself.

2. For each candidate entry, Directory Server performs the following tasks.

   1. Performs a base search to retrieve the entry.

   2. Checks whether the entry matches the filter provided for the search.

   3. Returns the entry to the client application if the entry matches the filter.