# Package org.apache.lucene.facet.taxonomy.directory

package org.apache.lucene.facet.taxonomy.directory
Taxonomy index implementation using on top of a Directory.

- Related Packages
  Package
  Description
  org.apache.lucene.facet.taxonomy
  Taxonomy of Categories.
  org.apache.lucene.facet.taxonomy.writercache
  Improves indexing time by caching a map of CategoryPath to their Ordinal.
- Class
  Description
  DirectoryTaxonomyReader
  A `TaxonomyReader` which retrieves stored taxonomy information from a `Directory`.
  DirectoryTaxonomyWriter
  `TaxonomyWriter` which uses a `Directory` to store the taxonomy information on disk, and keeps an additional in-memory cache of some or all categories.
  DirectoryTaxonomyWriter.DiskOrdinalMap
  `DirectoryTaxonomyWriter.OrdinalMap` maintained on file system
  DirectoryTaxonomyWriter.MemoryOrdinalMap
  `DirectoryTaxonomyWriter.OrdinalMap` maintained in memory
  DirectoryTaxonomyWriter.OrdinalMap
  Mapping from old ordinal to new ordinals, used when merging indexes with separate taxonomies.
  ReindexingEnrichedDirectoryTaxonomyWriter
  Use this `TaxonomyWriter` to append arbitrary fields to the ordinal documents in the taxonomy.