org.apache.lucene.codecs.bloom

## Class BloomFilteringPostingsFormat

- java.lang.Object
- - org.apache.lucene.codecs.PostingsFormat
  - - org.apache.lucene.codecs.bloom.BloomFilteringPostingsFormat

- All Implemented Interfaces:
    NamedSPILoader.NamedSPI

      public final class BloomFilteringPostingsFormat
      extends PostingsFormat

  A `PostingsFormat` useful for low doc-frequency fields such as primary keys. Bloom filters are maintained in a ".blm" file which offers "fast-fail" for reads in segments known to have no record of the key. A choice of delegate PostingsFormat is used to record all other Postings data.

  A choice of `BloomFilterFactory` can be passed to tailor Bloom Filter settings on a per-field basis. The default configuration is `DefaultBloomFilterFactory` which allocates a ~8mb bitset and hashes values using `MurmurHash2`. This should be suitable for most purposes.

  The format of the blm file is as follows:

  - BloomFilter (.blm) --> Header, DelegatePostingsFormatName, NumFilteredFields, FilterNumFilteredFields, Footer
  - Filter --> FieldNumber, FuzzySet
  - FuzzySet -->See `FuzzySet.serialize(DataOutput)`
  - Header --> `IndexHeader`
  - DelegatePostingsFormatName --> `String` The name of a ServiceProvider registered `PostingsFormat`
  - NumFilteredFields --> `Uint32`
  - FieldNumber --> `Uint32` The number of the field in this segment
  - Footer --> `CodecFooter`
  WARNING: This API is experimental and might change in incompatible ways in the next release.

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `static String` | `BLOOM_CODEC_NAME`
    `static int` | `VERSION_CURRENT`
    `static int` | `VERSION_START`

    - ### Fields inherited from class org.apache.lucene.codecs.PostingsFormat

      `EMPTY`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `BloomFilteringPostingsFormat()`
    `BloomFilteringPostingsFormat(PostingsFormat delegatePostingsFormat)` Creates Bloom filters for a selection of fields created in the index.
    `BloomFilteringPostingsFormat(PostingsFormat delegatePostingsFormat, BloomFilterFactory bloomFilterFactory)` Creates Bloom filters for a selection of fields created in the index.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `FieldsConsumer` | `fieldsConsumer(SegmentWriteState state)`
    `FieldsProducer` | `fieldsProducer(SegmentReadState state)`
    `String` | `toString()`

    - ### Methods inherited from class org.apache.lucene.codecs.PostingsFormat

      `availablePostingsFormats, forName, getName, reloadPostingsFormats`

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

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

- - ### Field Detail

    - #### BLOOM_CODEC_NAME

          public static final String BLOOM_CODEC_NAME

      See Also:
        Constant Field Values

    - #### VERSION_START

          public static final int VERSION_START

      See Also:
        Constant Field Values

    - #### VERSION_CURRENT

          public static final int VERSION_CURRENT

      See Also:
        Constant Field Values

  - ### Constructor Detail

    - #### BloomFilteringPostingsFormat

          public BloomFilteringPostingsFormat(PostingsFormat delegatePostingsFormat,
                                              BloomFilterFactory bloomFilterFactory)

      Creates Bloom filters for a selection of fields created in the index. This is recorded as a set of Bitsets held as a segment summary in an additional "blm" file. This PostingsFormat delegates to a choice of delegate PostingsFormat for encoding all other postings data.
      Parameters:
        `delegatePostingsFormat` - The PostingsFormat that records all the non-bloom filter data i.e. postings info.
        `bloomFilterFactory` - The `BloomFilterFactory` responsible for sizing BloomFilters appropriately

    - #### BloomFilteringPostingsFormat

          public BloomFilteringPostingsFormat(PostingsFormat delegatePostingsFormat)

      Creates Bloom filters for a selection of fields created in the index. This is recorded as a set of Bitsets held as a segment summary in an additional "blm" file. This PostingsFormat delegates to a choice of delegate PostingsFormat for encoding all other postings data. This choice of constructor defaults to the `DefaultBloomFilterFactory` for configuring per-field BloomFilters.
      Parameters:
        `delegatePostingsFormat` - The PostingsFormat that records all the non-bloom filter data i.e. postings info.

    - #### BloomFilteringPostingsFormat

          public BloomFilteringPostingsFormat()

  - ### Method Detail

    - #### fieldsConsumer

          public FieldsConsumer fieldsConsumer(SegmentWriteState state)
                                        throws IOException

      Specified by:
        `fieldsConsumer` in class `PostingsFormat`
      Throws:
        `IOException`

    - #### fieldsProducer

          public FieldsProducer fieldsProducer(SegmentReadState state)
                                        throws IOException

      Specified by:
        `fieldsProducer` in class `PostingsFormat`
      Throws:
        `IOException`

    - #### toString

          public String toString()

      Overrides:
        `toString` in class `PostingsFormat`

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