org.apache.lucene.search

Class UsageTrackingQueryCachingPolicy

java.lang.Object

org.apache.lucene.search.UsageTrackingQueryCachingPolicy

All Implemented Interfaces:

QueryCachingPolicy

public final class UsageTrackingQueryCachingPolicy
extends java.lang.Object
implements QueryCachingPolicy

A QueryCachingPolicy that tracks usage statistics of recently-used filters in order to decide on which filters are worth caching.

Field Summary

Fields

Modifier and Type	Field and Description
private FrequencyTrackingRingBuffer	recentlyUsedFilters
private static int	SENTINEL

Fields inherited from interface org.apache.lucene.search.QueryCachingPolicy

ALWAYS_CACHE

Constructor Summary

Constructors

Constructor and Description
UsageTrackingQueryCachingPolicy() Create a new instance with an history size of 256.
UsageTrackingQueryCachingPolicy(int historySize) Create a new instance.

Method Summary

Modifier and Type	Method and Description
(package private) int	frequency(Query query)
(package private) static boolean	isCheap(Query query)
(package private) static boolean	isCostly(Query query)
private static boolean	isPointQuery(Query query)
protected int	minFrequencyToCache(Query query) For a given query, return how many times it should appear in the history before being cached.
void	onUse(Query query) Callback that is called every time that a cached filter is used.
boolean	shouldCache(Query query) Whether the given Query is worth caching.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

SENTINEL

private static final int SENTINEL

See Also:

Constant Field Values

recentlyUsedFilters

private final FrequencyTrackingRingBuffer recentlyUsedFilters

Constructor Detail

UsageTrackingQueryCachingPolicy

public UsageTrackingQueryCachingPolicy(int historySize)

Create a new instance.

Parameters:

historySize - the number of recently used filters to track

UsageTrackingQueryCachingPolicy

public UsageTrackingQueryCachingPolicy()

Create a new instance with an history size of 256.

Method Detail

isPointQuery

private static boolean isPointQuery(Query query)

isCostly

static boolean isCostly(Query query)

isCheap

static boolean isCheap(Query query)

minFrequencyToCache

protected int minFrequencyToCache(Query query)

For a given query, return how many times it should appear in the history before being cached.

onUse

public void onUse(Query query)

Description copied from interface: QueryCachingPolicy

Callback that is called every time that a cached filter is used. This is typically useful if the policy wants to track usage statistics in order to make decisions.

Specified by:

onUse in interface QueryCachingPolicy

frequency

int frequency(Query query)

shouldCache

public boolean shouldCache(Query query)
                    throws java.io.IOException

Description copied from interface: QueryCachingPolicy

Whether the given Query is worth caching. This method will be called by the QueryCache to know whether to cache. It will first attempt to load a DocIdSet from the cache. If it is not cached yet and this method returns true then a cache entry will be generated. Otherwise an uncached scorer will be returned.

Specified by:

shouldCache in interface QueryCachingPolicy

Throws:

java.io.IOException