org.apache.lucene.facet.taxonomy.writercache.lru
Class LruTaxonomyWriterCache

java.lang.Object
  org.apache.lucene.facet.taxonomy.writercache.lru.LruTaxonomyWriterCache

All Implemented Interfaces:

TaxonomyWriterCache

public class LruTaxonomyWriterCache
extends Object
implements TaxonomyWriterCache

LRU TaxonomyWriterCache - good choice for huge taxonomies.

WARNING: This API is experimental and might change in incompatible ways in the next release.

Nested Class Summary

static class

LruTaxonomyWriterCache.LRUType

Constructor Summary

LruTaxonomyWriterCache(int cacheSize)

LruTaxonomyWriterCache(int cacheSize, LruTaxonomyWriterCache.LRUType lruType)

Method Summary

void	close() Let go of whatever resources the cache is holding.
int	get(CategoryPath categoryPath) Lookup a category in the cache, returning its ordinal, or a negative number if the category is not in the cache.
int	get(CategoryPath categoryPath, int length) Like TaxonomyWriterCache.get(CategoryPath), but for a given prefix of the category path.
boolean	hasRoom(int n) Sometimes the cache is either unlimited in size, or limited by a very big size, and in that case when we add a lot of categories it might make sense to pre-load the cache with all the existing categories.
boolean	put(CategoryPath categoryPath, int ordinal) Add a category to the cache, with the given ordinal as the value.
boolean	put(CategoryPath categoryPath, int prefixLen, int ordinal) Like TaxonomyWriterCache.put(CategoryPath, int), but for a given prefix of the category path.

Methods inherited from class java.lang.Object

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

Constructor Detail

LruTaxonomyWriterCache

public LruTaxonomyWriterCache(int cacheSize)

LruTaxonomyWriterCache

public LruTaxonomyWriterCache(int cacheSize,
                              LruTaxonomyWriterCache.LRUType lruType)

Method Detail

hasRoom

public boolean hasRoom(int n)

Description copied from interface: TaxonomyWriterCache

Sometimes the cache is either unlimited in size, or limited by a very big size, and in that case when we add a lot of categories it might make sense to pre-load the cache with all the existing categories. However, this pre-load does not make sense when the allowed cache size is small. The hasRoom() method allows to differentiate between these cases.

After hasRoom(n) returned true, the following n put() should return false (meaning that the cache was not cleared).

Specified by:

hasRoom in interface TaxonomyWriterCache

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

get

public int get(CategoryPath categoryPath)

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

get

public int get(CategoryPath categoryPath,
               int length)

Description copied from interface: TaxonomyWriterCache

Like TaxonomyWriterCache.get(CategoryPath), but for a given prefix of the category path.

If the given length is negative or bigger than the path's actual length, the full path is taken.

Specified by:

get in interface TaxonomyWriterCache

put

public boolean put(CategoryPath categoryPath,
                   int ordinal)

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

put

public boolean put(CategoryPath categoryPath,
                   int prefixLen,
                   int ordinal)

Description copied from interface: TaxonomyWriterCache

Like TaxonomyWriterCache.put(CategoryPath, int), but for a given prefix of the category path.

If the given length is negative or bigger than the path's actual length, the full path is taken.

Specified by:

put in interface TaxonomyWriterCache