Package org.apache.lucene.facet.taxonomy.writercache

Class LruTaxonomyWriterCache

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

  • Constructor Details

  • Method Details

    • 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

    • 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

    • size

      public int size()
      Description copied from interface: TaxonomyWriterCache
      How many labels are currently stored in the cache.
      Specified by:
      size in interface TaxonomyWriterCache

    • get

      public int get(FacetLabel 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

    • put

      public boolean put(FacetLabel 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