org.apache.lucene.facet.taxonomy.directory

## Interface DirectoryTaxonomyWriter.OrdinalMap

- All Known Implementing Classes:
    DirectoryTaxonomyWriter.DiskOrdinalMap, DirectoryTaxonomyWriter.MemoryOrdinalMap
  Enclosing class:
    DirectoryTaxonomyWriter

      public static interface DirectoryTaxonomyWriter.OrdinalMap

  Mapping from old ordinal to new ordinals, used when merging indexes wit separate taxonomies.

  addToTaxonomies() merges one or more taxonomies into the given taxonomy (this). An OrdinalMap is filled for each of the added taxonomies, containing the new ordinal (in the merged taxonomy) of each of the categories in the old taxonomy.

  There exist two implementations of OrdinalMap: MemoryOrdinalMap and DiskOrdinalMap. As their names suggest, the former keeps the map in memory and the latter in a temporary disk file. Because these maps will later be needed one by one (to remap the counting lists), not all at the same time, it is recommended to put the first taxonomy's map in memory, and all the rest on disk (later to be automatically read into memory one by one, when needed).

- - ### Method Summary

    All Methods Instance Methods Abstract Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `addDone()` Call addDone() to say that all addMapping() have been done.
    `void` | `addMapping(int origOrdinal, int newOrdinal)` Record a mapping.
    `int[]` | `getMap()` Return the map from the taxonomy's original (consecutive) ordinals to the new taxonomy's ordinals.
    `void` | `setSize(int size)` Set the size of the map.

- - ### Method Detail

    - #### setSize

          void setSize(int size)
                throws IOException

      Set the size of the map. This MUST be called before addMapping(). It is assumed (but not verified) that addMapping() will then be called exactly 'size' times, with different origOrdinals between 0 and size-1.
      Throws:
        `IOException`

    - #### addMapping

          void addMapping(int origOrdinal,
                          int newOrdinal)
                   throws IOException

      Record a mapping.
      Throws:
        `IOException`

    - #### addDone

          void addDone()
                throws IOException

      Call addDone() to say that all addMapping() have been done. In some implementations this might free some resources.
      Throws:
        `IOException`

    - #### getMap

          int[] getMap()
                throws IOException

      Return the map from the taxonomy's original (consecutive) ordinals to the new taxonomy's ordinals. If the map has to be read from disk and ordered appropriately, it is done when getMap() is called. getMap() should only be called once, and only when the map is actually needed. Calling it will also free all resources that the map might be holding (such as temporary disk space), other than the returned int[].
      Throws:
        `IOException`

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