org.apache.lucene.search

Class XUsageTrackingQueryCachingPolicy

java.lang.Object

org.apache.lucene.search.XUsageTrackingQueryCachingPolicy

All Implemented Interfaces:

org.apache.lucene.search.QueryCachingPolicy

public final class XUsageTrackingQueryCachingPolicy
extends Object
implements org.apache.lucene.search.QueryCachingPolicy

A QueryCachingPolicy that tracks usage statistics of recently-used filters in order to decide on which filters are worth caching. It also uses some heuristics on segments, filters and the doc id sets that they produce in order to cache more aggressively when the execution cost significantly outweighs the caching overhead.

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.lucene.search.QueryCachingPolicy

org.apache.lucene.search.QueryCachingPolicy.CacheOnLargeSegments

Field Summary

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

ALWAYS_CACHE

Constructor Summary

Constructors

Constructor and Description
XUsageTrackingQueryCachingPolicy() Create a new instance with an history size of 256.
XUsageTrackingQueryCachingPolicy(int minIndexSize, float minSizeRatio, int historySize) Create a new instance.

Method Summary

Modifier and Type	Method and Description
protected int	minFrequencyToCache(org.apache.lucene.search.Query query) For a given query, return how many times it should appear in the history before being cached.
void	onUse(org.apache.lucene.search.Query query)
boolean	shouldCache(org.apache.lucene.search.Query query, org.apache.lucene.index.LeafReaderContext context)

Methods inherited from class java.lang.Object

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

Constructor Detail

XUsageTrackingQueryCachingPolicy

public XUsageTrackingQueryCachingPolicy(int minIndexSize,
                                        float minSizeRatio,
                                        int historySize)

Create a new instance.

Parameters:

minIndexSize - the minimum size of the top-level index

minSizeRatio - the minimum size ratio for segments to be cached, see QueryCachingPolicy.CacheOnLargeSegments

historySize - the number of recently used filters to track

XUsageTrackingQueryCachingPolicy

public XUsageTrackingQueryCachingPolicy()

Create a new instance with an history size of 256.

Method Detail

minFrequencyToCache

protected int minFrequencyToCache(org.apache.lucene.search.Query query)

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

onUse

public void onUse(org.apache.lucene.search.Query query)

Specified by:

onUse in interface org.apache.lucene.search.QueryCachingPolicy

shouldCache

public boolean shouldCache(org.apache.lucene.search.Query query,
                           org.apache.lucene.index.LeafReaderContext context)
                    throws IOException

Specified by:

shouldCache in interface org.apache.lucene.search.QueryCachingPolicy

Throws:

IOException