java.lang.Object
- org.apache.lucene.search.SortField

Direct Known Subclasses:

SortedNumericSortField, SortedSetSortField
```
public class SortField
extends Object
```
Stores information about how to sort documents by terms in an individual field. Fields must be indexed in order to sort by them.
Created: Feb 11, 2004 1:25:29 PM

Since:

lucene 1.4

See Also:

Sort

Nested Class Summary

Nested Classes
Modifier and Type	Class	Description
`static class`	`SortField.Provider`	A SortFieldProvider for field sorts
`static class`	`SortField.Type`	Specifies the type of the terms to be sorted, or special types such as CUSTOM

Field Summary

Fields
Modifier and Type	Field	Description
`static SortField`	`FIELD_DOC`	Represents sorting by document number (index order).
`static SortField`	`FIELD_SCORE`	Represents sorting by document score (relevance).
`protected Object`	`missingValue`
`static Object`	`STRING_FIRST`	Pass this to `setMissingValue(java.lang.Object)` to have missing string values sort first.
`static Object`	`STRING_LAST`	Pass this to `setMissingValue(java.lang.Object)` to have missing string values sort last.

Constructor Summary

Constructors
Constructor	Description
`SortField(String field, FieldComparatorSource comparator)`	Creates a sort with a custom comparison function.
`SortField(String field, FieldComparatorSource comparator, boolean reverse)`	Creates a sort, possibly in reverse, with a custom comparison function.
`SortField(String field, SortField.Type type)`	Creates a sort by terms in the given field with the type of term values explicitly given.
`SortField(String field, SortField.Type type, boolean reverse)`	Creates a sort, possibly in reverse, by terms in the given field with the type of term values explicitly given.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`boolean`	`equals(Object o)`	Returns true if `o` is equal to this.
`Comparator<BytesRef>`	`getBytesComparator()`
`FieldComparator<?>`	`getComparator(int numHits, int sortPos)`	Returns the `FieldComparator` to use for sorting.
`FieldComparatorSource`	`getComparatorSource()`	Returns the `FieldComparatorSource` used for custom sorting
`String`	`getField()`	Returns the name of the field.
`IndexSorter`	`getIndexSorter()`	Returns an `IndexSorter` used for sorting index segments by this SortField.
`Object`	`getMissingValue()`	Return the value to use for documents that don't have a value.
`boolean`	`getReverse()`	Returns whether the sort should be reversed.
`SortField.Type`	`getType()`	Returns the type of contents in the field.
`int`	`hashCode()`	Returns a hash code for this `SortField` instance.
`boolean`	`needsScores()`	Whether the relevance score is needed to sort documents.
`protected static SortField.Type`	`readType(DataInput in)`
`SortField`	`rewrite(IndexSearcher searcher)`	Rewrites this SortField, returning a new SortField if a change is made.
`void`	`setBytesComparator(Comparator<BytesRef> b)`
`void`	`setMissingValue(Object missingValue)`	Set the value to use for documents that don't have a value.
`String`	`toString()`

Methods inherited from class java.lang.Object
clone, finalize, getClass, notify, notifyAll, wait, wait, wait

- Field Detail
  - FIELD_SCORE
```
public static final SortField FIELD_SCORE
```
    Represents sorting by document score (relevance).
  - FIELD_DOC
```
public static final SortField FIELD_DOC
```
    Represents sorting by document number (index order).
  - missingValue
```
protected Object missingValue
```
  - STRING_FIRST
```
public static final Object STRING_FIRST
```
    Pass this to setMissingValue(java.lang.Object) to have missing string values sort first.
  - STRING_LAST
```
public static final Object STRING_LAST
```
    Pass this to setMissingValue(java.lang.Object) to have missing string values sort last.
- Constructor Detail
  - SortField
```
public SortField(String field,
                 SortField.Type type)
```
    Creates a sort by terms in the given field with the type of term values explicitly given.
    
    Parameters:
    
    field - Name of field to sort by. Can be null if type is SCORE or DOC.
    
    type - Type of values in the terms.
  - SortField
```
public SortField(String field,
                 SortField.Type type,
                 boolean reverse)
```
    Creates a sort, possibly in reverse, by terms in the given field with the type of term values explicitly given.
    
    Parameters:
    
    field - Name of field to sort by. Can be null if type is SCORE or DOC.
    
    type - Type of values in the terms.
    
    reverse - True if natural order should be reversed.
  - SortField
```
public SortField(String field,
                 FieldComparatorSource comparator)
```
    Creates a sort with a custom comparison function.
    
    Parameters:
    
    field - Name of field to sort by; cannot be null.
    
    comparator - Returns a comparator for sorting hits.
  - SortField
```
public SortField(String field,
                 FieldComparatorSource comparator,
                 boolean reverse)
```
    Creates a sort, possibly in reverse, with a custom comparison function.
    
    Parameters:
    
    field - Name of field to sort by; cannot be null.
    
    comparator - Returns a comparator for sorting hits.
    
    reverse - True if natural order should be reversed.
- Method Detail
  - readType
```
protected static SortField.Type readType(DataInput in)
                                  throws IOException
```
    Throws:
    
    IOException
  - getMissingValue
```
public Object getMissingValue()
```
    Return the value to use for documents that don't have a value. A value of null indicates that default should be used.
  - setMissingValue
```
public void setMissingValue(Object missingValue)
```
    Set the value to use for documents that don't have a value.
  - getField
```
public String getField()
```
    Returns the name of the field. Could return null if the sort is by SCORE or DOC.
    
    Returns:
    
    Name of field, possibly null.
  - getType
```
public SortField.Type getType()
```
    Returns the type of contents in the field.
    
    Returns:
    
    One of the constants SCORE, DOC, STRING, INT or FLOAT.
  - getReverse
```
public boolean getReverse()
```
    Returns whether the sort should be reversed.
    
    Returns:
    
    True if natural order should be reversed.
  - getComparatorSource
```
public FieldComparatorSource getComparatorSource()
```
    Returns the FieldComparatorSource used for custom sorting
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object
  - equals
```
public boolean equals(Object o)
```
    Returns true if o is equal to this. If a FieldComparatorSource was provided, it must properly implement equals (unless a singleton is always used).
    
    Overrides:
    
    equals in class Object
  - hashCode
```
public int hashCode()
```
    Returns a hash code for this SortField instance. If a FieldComparatorSource was provided, it must properly implement hashCode (unless a singleton is always used).
    
    Overrides:
    
    hashCode in class Object
  - setBytesComparator
```
public void setBytesComparator(Comparator<BytesRef> b)
```
  - getBytesComparator
```
public Comparator<BytesRef> getBytesComparator()
```
  - getComparator
```
public FieldComparator<?> getComparator(int numHits,
                                        int sortPos)
```
    Returns the FieldComparator to use for sorting.
    
    Parameters:
    
    numHits - number of top hits the queue will store
    
    sortPos - position of this SortField within Sort. The comparator is primary if sortPos==0, secondary if sortPos==1, etc. Some comparators can optimize themselves when they are the primary sort.
    
    Returns:
    
    FieldComparator to use when sorting
    
    WARNING: This API is experimental and might change in incompatible ways in the next release.
  - rewrite
```
public SortField rewrite(IndexSearcher searcher)
                  throws IOException
```
    Rewrites this SortField, returning a new SortField if a change is made. Subclasses should override this define their rewriting behavior when this SortField is of type SortField.Type.REWRITEABLE
    
    Parameters:
    
    searcher - IndexSearcher to use during rewriting
    
    Returns:
    
    New rewritten SortField, or this if nothing has changed.
    
    Throws:
    
    IOException - Can be thrown by the rewriting
    
    WARNING: This API is experimental and might change in incompatible ways in the next release.
  - needsScores
```
public boolean needsScores()
```
    Whether the relevance score is needed to sort documents.
  - getIndexSorter
```
public IndexSorter getIndexSorter()
```
    Returns an IndexSorter used for sorting index segments by this SortField. If the SortField cannot be used for index sorting (for example, if it uses scores or other query-dependent values) then this method should return null SortFields that implement this method should also implement a companion SortFieldProvider to serialize and deserialize the sort in index segment headers
    
    WARNING: This API is experimental and might change in incompatible ways in the next release.

Class SortField

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

FIELD_SCORE

FIELD_DOC

missingValue

STRING_FIRST

STRING_LAST

Constructor Detail

SortField

SortField

SortField

SortField

Method Detail

readType

getMissingValue

setMissingValue

getField

getType

getReverse

getComparatorSource

toString

equals

hashCode

setBytesComparator

getBytesComparator

getComparator

rewrite

needsScores

getIndexSorter