org.apache.lucene.codecs

## Class FieldsConsumer

- java.lang.Object
- - org.apache.lucene.codecs.FieldsConsumer

- All Implemented Interfaces:
    Closeable, AutoCloseable
  Direct Known Subclasses:
    BlockTreeTermsWriter

      public abstract class FieldsConsumer
      extends Object
      implements Closeable

  Abstract API that consumes terms, doc, freq, prox, offset and payloads postings. Concrete implementations of this actually do "something" with the postings (write it into the index in a specific format).
  WARNING: This API is experimental and might change in incompatible ways in the next release.

- - ### Constructor Summary

    Constructors
    Modifier | Constructor and Description
    --- | ---
    `protected` | `FieldsConsumer()` Sole constructor.

  - ### Method Summary

    All Methods Instance Methods Abstract Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `abstract void` | `close()`
    `void` | `merge(MergeState mergeState, NormsProducer norms)` Merges in the fields from the readers in `mergeState`.
    `abstract void` | `write(Fields fields, NormsProducer norms)` Write all fields, terms and postings.

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

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

- - ### Constructor Detail

    - #### FieldsConsumer

          protected FieldsConsumer()

      Sole constructor. (For invocation by subclass constructors, typically implicit.)

  - ### Method Detail

    - #### write

          public abstract void write(Fields fields,
                                     NormsProducer norms)
                              throws IOException

      Write all fields, terms and postings. This the "pull" API, allowing you to iterate more than once over the postings, somewhat analogous to using a DOM API to traverse an XML tree.

      Notes:

      - You must compute index statistics, including each Term's docFreq and totalTermFreq, as well as the summary sumTotalTermFreq, sumTotalDocFreq and docCount.
      - You must skip terms that have no docs and fields that have no terms, even though the provided Fields API will expose them; this typically requires lazily writing the field or term until you've actually seen the first term or document.
      - The provided Fields instance is limited: you cannot call any methods that return statistics/counts; you cannot pass a non-null live docs when pulling docs/positions enums.
      Throws:
        `IOException`

    - #### merge

          public void merge(MergeState mergeState,
                            NormsProducer norms)
                     throws IOException

      Merges in the fields from the readers in `mergeState`. The default implementation skips and maps around deleted documents, and calls `write(Fields,NormsProducer)`. Implementations can override this method for more sophisticated merging (bulk-byte copying, etc).
      Throws:
        `IOException`

    - #### close

          public abstract void close()
                              throws IOException

      Specified by:
        `close` in interface `Closeable`
      Specified by:
        `close` in interface `AutoCloseable`
      Throws:
        `IOException`

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