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