org.apache.lucene.facet.taxonomy.writercache

Class UTF8TaxonomyWriterCache

java.lang.Object

org.apache.lucene.facet.taxonomy.writercache.UTF8TaxonomyWriterCache

All Implemented Interfaces:

TaxonomyWriterCache

public final class UTF8TaxonomyWriterCache
extends java.lang.Object
implements TaxonomyWriterCache

A "cache" that never frees memory, and stores labels in a BytesRefHash (utf-8 encoding).

Constructor Summary

Constructors

Constructor and Description
UTF8TaxonomyWriterCache() Sole constructor.

Method Summary

Modifier and Type	Method and Description
void	clear() Clears the content of the cache.
void	close() Let go of whatever resources the cache is holding.
int	get(FacetLabel label) Lookup a category in the cache, returning its ordinal, or a negative number if the category is not in the cache.
boolean	isFull() Returns true if the cache is full, such that the next TaxonomyWriterCache.put(org.apache.lucene.facet.taxonomy.FacetLabel, int) will evict entries from it, false otherwise.
boolean	put(FacetLabel label, int ord) Add a category to the cache, with the given ordinal as the value.
long	ramBytesUsed()
int	size() How many labels are currently stored in the cache.

Methods inherited from class java.lang.Object

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

Constructor Detail

UTF8TaxonomyWriterCache

public UTF8TaxonomyWriterCache()

Sole constructor.

Method Detail

get

public int get(FacetLabel label)

Description copied from interface: TaxonomyWriterCache

Lookup a category in the cache, returning its ordinal, or a negative number if the category is not in the cache.

It is up to the caller to remember what a negative response means: If the caller knows the cache is complete (it was initially fed with all the categories, and since then put() never returned true) it means the category does not exist. Otherwise, the category might still exist, but just be missing from the cache.

Specified by:

get in interface TaxonomyWriterCache

put

public boolean put(FacetLabel label,
                   int ord)

Description copied from interface: TaxonomyWriterCache

Add a category to the cache, with the given ordinal as the value.

If the implementation keeps only a partial cache (e.g., an LRU cache) and finds that its cache is full, it should clear up part of the cache and return true. Otherwise, it should return false.

The reason why the caller needs to know if part of the cache was cleared is that in that case it will have to commit its on-disk index (so that all the latest category additions can be searched on disk, if we can't rely on the cache to contain them).

Ordinals should be non-negative. Currently there is no defined way to specify that a cache should remember a category does NOT exist. It doesn't really matter, because normally the next thing we do after finding that a category does not exist is to add it.

Specified by:

put in interface TaxonomyWriterCache

isFull

public boolean isFull()

Description copied from interface: TaxonomyWriterCache

Returns true if the cache is full, such that the next TaxonomyWriterCache.put(org.apache.lucene.facet.taxonomy.FacetLabel, int) will evict entries from it, false otherwise.

Specified by:

isFull in interface TaxonomyWriterCache

clear

public void clear()

Description copied from interface: TaxonomyWriterCache

Clears the content of the cache. Unlike TaxonomyWriterCache.close(), the caller can assume that the cache is still operable after this method returns.

Specified by:

clear in interface TaxonomyWriterCache

size

public int size()

How many labels are currently stored in the cache.

Specified by:

size in interface TaxonomyWriterCache

ramBytesUsed

public long ramBytesUsed()

close

public void close()

Description copied from interface: TaxonomyWriterCache

Let go of whatever resources the cache is holding. After a close(), this object can no longer be used.

Specified by:

close in interface TaxonomyWriterCache