Speeding Solr through Solr caching

Many times, the queries that are run on search are repetitive in nature. In such cases, the presence of a cache brings down the average response time for search results. Apache Solr provides a caching mechanism on top of the index data. This cache, unlike a normal cache, does not carry any expiry (persistent cache). It is associated with IndexWriter. The following are the three different types of cache supported by Solr:

• LRUCache: This is Least Recently Used (based on synchronized LinkedHashMap) (default)

• FastLRUCache: This is a newer form of cache and is expected to be faster than all the others

• LFUCache: This is Least Frequently Used (based on ConcurrentHashMap)

The following are the common parameters for the cache in solrconfig.xml:

Parameter	Description
class	You can specify the type of cache you wish to attach, that is, LRUCache, FastLRUCache, or LFUCache.
size	This is the maximum size a cache can reach.
initialSize	This is the initial...