Package org.apache.lucene.index

# Class DocValues

java.lang.Object
org.apache.lucene.index.DocValues

public final class DocValues extends Object
This class contains utility methods and constants for DocValues

- ## Method Summary

  Modifier and Type
  Method
  Description
  `static final BinaryDocValues`
  `emptyBinary()`
  An empty `BinaryDocValues` which returns no documents
  `static final NumericDocValues`
  `emptyNumeric()`
  An empty NumericDocValues which returns no documents
  `static final SortedDocValues`
  `emptySorted()`
  An empty SortedDocValues which returns `BytesRef.EMPTY_BYTES` for every document
  `static final SortedNumericDocValues`
  `emptySortedNumeric()`
  An empty SortedNumericDocValues which returns zero values for every document
  `static final SortedSetDocValues`
  `emptySortedSet()`
  An empty SortedDocValues which returns `BytesRef.EMPTY_BYTES` for every document
  `static BinaryDocValues`
  `getBinary(LeafReader reader, String field)`
  Returns BinaryDocValues for the field, or `emptyBinary()` if it has none.
  `static NumericDocValues`
  `getNumeric(LeafReader reader, String field)`
  Returns NumericDocValues for the field, or `emptyNumeric()` if it has none.
  `static SortedDocValues`
  `getSorted(LeafReader reader, String field)`
  Returns SortedDocValues for the field, or `emptySorted()` if it has none.
  `static SortedNumericDocValues`
  `getSortedNumeric(LeafReader reader, String field)`
  Returns SortedNumericDocValues for the field, or `emptySortedNumeric()` if it has none.
  `static SortedSetDocValues`
  `getSortedSet(LeafReader reader, String field)`
  Returns SortedSetDocValues for the field, or `emptySortedSet()` if it has none.
  `static boolean`
  `isCacheable(LeafReaderContext ctx, String... fields)`
  Returns `true` if the specified docvalues fields have not been updated
  `static SortedNumericDocValues`
  `singleton(NumericDocValues dv)`
  Returns a multi-valued view over the provided NumericDocValues
  `static SortedSetDocValues`
  `singleton(SortedDocValues dv)`
  Returns a multi-valued view over the provided SortedDocValues
  `static NumericDocValues`
  `unwrapSingleton(SortedNumericDocValues dv)`
  Returns a single-valued view of the SortedNumericDocValues, if it was previously wrapped with `singleton(NumericDocValues)`, or null.
  `static SortedDocValues`
  `unwrapSingleton(SortedSetDocValues dv)`
  Returns a single-valued view of the SortedSetDocValues, if it was previously wrapped with `singleton(SortedDocValues)`, or null.

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

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

- ## Method Details

  - ### emptyBinary

    public static final BinaryDocValues emptyBinary()
    An empty `BinaryDocValues` which returns no documents

  - ### emptyNumeric

    public static final NumericDocValues emptyNumeric()
    An empty NumericDocValues which returns no documents

  - ### emptySorted

    public static final SortedDocValues emptySorted()
    An empty SortedDocValues which returns `BytesRef.EMPTY_BYTES` for every document

  - ### emptySortedNumeric

    public static final SortedNumericDocValues emptySortedNumeric()
    An empty SortedNumericDocValues which returns zero values for every document

  - ### emptySortedSet

    public static final SortedSetDocValues emptySortedSet()
    An empty SortedDocValues which returns `BytesRef.EMPTY_BYTES` for every document

  - ### singleton

    public static SortedSetDocValues singleton(SortedDocValues dv)
    Returns a multi-valued view over the provided SortedDocValues

  - ### unwrapSingleton

    public static SortedDocValues unwrapSingleton(SortedSetDocValues dv)
    Returns a single-valued view of the SortedSetDocValues, if it was previously wrapped with `singleton(SortedDocValues)`, or null.

  - ### unwrapSingleton

    public static NumericDocValues unwrapSingleton(SortedNumericDocValues dv)
    Returns a single-valued view of the SortedNumericDocValues, if it was previously wrapped with `singleton(NumericDocValues)`, or null.

  - ### singleton

    public static SortedNumericDocValues singleton(NumericDocValues dv)
    Returns a multi-valued view over the provided NumericDocValues

  - ### getNumeric

    public static NumericDocValues getNumeric(LeafReader reader, String field) throws IOException
    Returns NumericDocValues for the field, or `emptyNumeric()` if it has none.
    Returns:
      docvalues instance, or an empty instance if `field` does not exist in this reader.
    Throws:
      `IllegalStateException` - if `field` exists, but was not indexed with docvalues.
      `IllegalStateException` - if `field` has docvalues, but the type is not `DocValuesType.NUMERIC`.
      `IOException` - if an I/O error occurs.

  - ### getBinary

    public static BinaryDocValues getBinary(LeafReader reader, String field) throws IOException
    Returns BinaryDocValues for the field, or `emptyBinary()` if it has none.
    Returns:
      docvalues instance, or an empty instance if `field` does not exist in this reader.
    Throws:
      `IllegalStateException` - if `field` exists, but was not indexed with docvalues.
      `IllegalStateException` - if `field` has docvalues, but the type is not `DocValuesType.BINARY`.
      `IOException` - if an I/O error occurs.

  - ### getSorted

    public static SortedDocValues getSorted(LeafReader reader, String field) throws IOException
    Returns SortedDocValues for the field, or `emptySorted()` if it has none.
    Returns:
      docvalues instance, or an empty instance if `field` does not exist in this reader.
    Throws:
      `IllegalStateException` - if `field` exists, but was not indexed with docvalues.
      `IllegalStateException` - if `field` has docvalues, but the type is not `DocValuesType.SORTED`.
      `IOException` - if an I/O error occurs.

  - ### getSortedNumeric

    public static SortedNumericDocValues getSortedNumeric(LeafReader reader, String field) throws IOException
    Returns SortedNumericDocValues for the field, or `emptySortedNumeric()` if it has none.
    Returns:
      docvalues instance, or an empty instance if `field` does not exist in this reader.
    Throws:
      `IllegalStateException` - if `field` exists, but was not indexed with docvalues.
      `IllegalStateException` - if `field` has docvalues, but the type is not `DocValuesType.SORTED_NUMERIC` or `DocValuesType.NUMERIC`.
      `IOException` - if an I/O error occurs.

  - ### getSortedSet

    public static SortedSetDocValues getSortedSet(LeafReader reader, String field) throws IOException
    Returns SortedSetDocValues for the field, or `emptySortedSet()` if it has none.
    Returns:
      docvalues instance, or an empty instance if `field` does not exist in this reader.
    Throws:
      `IllegalStateException` - if `field` exists, but was not indexed with docvalues.
      `IllegalStateException` - if `field` has docvalues, but the type is not `DocValuesType.SORTED_SET` or `DocValuesType.SORTED`.
      `IOException` - if an I/O error occurs.

  - ### isCacheable

    public static boolean isCacheable(LeafReaderContext ctx, String... fields)
    Returns `true` if the specified docvalues fields have not been updated