org.apache.lucene.codecs.compressing

## Class CompressingStoredFieldsFormat

- java.lang.Object
- - org.apache.lucene.codecs.StoredFieldsFormat
  - - org.apache.lucene.codecs.compressing.CompressingStoredFieldsFormat

-     public class CompressingStoredFieldsFormat
      extends StoredFieldsFormat

  A `StoredFieldsFormat` that compresses documents in chunks in order to improve the compression ratio.

  For a chunk size of `chunkSize` bytes, this `StoredFieldsFormat` does not support documents larger than (`231 - chunkSize`) bytes.

  For optimal performance, you should use a `MergePolicy` that returns segments that have the biggest byte size first.

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

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `CompressingStoredFieldsFormat(String formatName, CompressionMode compressionMode, int chunkSize, int maxDocsPerChunk, int blockShift)` Create a new `CompressingStoredFieldsFormat` with an empty segment suffix.
    `CompressingStoredFieldsFormat(String formatName, String segmentSuffix, CompressionMode compressionMode, int chunkSize, int maxDocsPerChunk, int blockShift)` Create a new `CompressingStoredFieldsFormat`.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `StoredFieldsReader` | `fieldsReader(Directory directory, SegmentInfo si, FieldInfos fn, IOContext context)` Returns a `StoredFieldsReader` to load stored fields.
    `StoredFieldsWriter` | `fieldsWriter(Directory directory, SegmentInfo si, IOContext context)` Returns a `StoredFieldsWriter` to write stored fields.
    `String` | `toString()`

    - ### Methods inherited from class java.lang.Object

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

- - ### Constructor Detail

    - #### CompressingStoredFieldsFormat

          public CompressingStoredFieldsFormat(String formatName,
                                               CompressionMode compressionMode,
                                               int chunkSize,
                                               int maxDocsPerChunk,
                                               int blockShift)

      Create a new `CompressingStoredFieldsFormat` with an empty segment suffix.
      See Also:
        `CompressingStoredFieldsFormat(String, String, CompressionMode, int, int, int)`

    - #### CompressingStoredFieldsFormat

          public CompressingStoredFieldsFormat(String formatName,
                                               String segmentSuffix,
                                               CompressionMode compressionMode,
                                               int chunkSize,
                                               int maxDocsPerChunk,
                                               int blockShift)

      Create a new `CompressingStoredFieldsFormat`.

      `formatName` is the name of the format. This name will be used in the file formats to perform `codec header checks`.

      `segmentSuffix` is the segment suffix. This suffix is added to the result file name only if it's not the empty string.

      The `compressionMode` parameter allows you to choose between compression algorithms that have various compression and decompression speeds so that you can pick the one that best fits your indexing and searching throughput. You should never instantiate two `CompressingStoredFieldsFormat`s that have the same name but different `CompressionMode`s.

      `chunkSize` is the minimum byte size of a chunk of documents. A value of `1` can make sense if there is redundancy across fields. `maxDocsPerChunk` is an upperbound on how many docs may be stored in a single chunk. This is to bound the cpu costs for highly compressible data.

      Higher values of `chunkSize` should improve the compression ratio but will require more memory at indexing time and might make document loading a little slower (depending on the size of your OS cache compared to the size of your index).

      Parameters:
        `formatName` - the name of the `StoredFieldsFormat`
        `compressionMode` - the `CompressionMode` to use
        `chunkSize` - the minimum number of bytes of a single chunk of stored documents
        `maxDocsPerChunk` - the maximum number of documents in a single chunk
        `blockShift` - the log in base 2 of number of chunks to store in an index block
      See Also:
        `CompressionMode`

  - ### Method Detail

    - #### fieldsReader

          public StoredFieldsReader fieldsReader(Directory directory,
                                                 SegmentInfo si,
                                                 FieldInfos fn,
                                                 IOContext context)
                                          throws IOException

      Description copied from class: `StoredFieldsFormat`
      Returns a `StoredFieldsReader` to load stored fields.
      Specified by:
        `fieldsReader` in class `StoredFieldsFormat`
      Throws:
        `IOException`

    - #### fieldsWriter

          public StoredFieldsWriter fieldsWriter(Directory directory,
                                                 SegmentInfo si,
                                                 IOContext context)
                                          throws IOException

      Description copied from class: `StoredFieldsFormat`
      Returns a `StoredFieldsWriter` to write stored fields.
      Specified by:
        `fieldsWriter` in class `StoredFieldsFormat`
      Throws:
        `IOException`

    - #### toString

          public String toString()

      Overrides:
        `toString` in class `Object`

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