Class Sort

Encapsulates sort criteria for returned hits.

The fields used to determine sort order must be carefully chosen. Documents must contain a single term in such a field, and the value of the term should indicate the document's relative position in a given sort order. The field must be indexed, but should not be tokenized, and does not need to be stored (unless you happen to want it back with the rest of your document data). In other words:

document.Add(new Field("byNumber", x.ToString(CultureInfo.InvariantCulture), Field.Store.NO, Field.Index.NOT_ANALYZED));

Valid Types of Values

There are four possible kinds of term values which may be put into sorting fields: ints, longs, floats, or strings. Unless SortField objects are specified, the type of value in the field is determined by parsing the first term in the field.

int term values should contain only digits and an optional preceding negative sign. Values must be base 10 and in the range MinValue and MaxValue inclusive. Documents which should appear first in the sort should have low value integers, later documents high values (i.e. the documents should be numbered 1..n where 1 is the first and n the last).

long term values should contain only digits and an optional preceding negative sign. Values must be base 10 and in the range MinValue and MaxValue inclusive. Documents which should appear first in the sort should have low value integers, later documents high values.

float term values should conform to values accepted by float (except that NaN and Infinity are not supported). Documents which should appear first in the sort should have low values, later documents high values.

string term values can contain any valid string, but should not be tokenized. The values are sorted according to their comparable natural order (Ordinal). Note that using this type of term value has higher memory requirements than the other two types.

Object Reuse

One of these objects can be used multiple times and the sort order changed between usages.

This class is thread safe.

Memory Usage

Sorting uses of caches of term values maintained by the internal HitQueue(s). The cache is static and contains an int or float array of length IndexReader.MaxDoc for each field name for which a sort is performed. In other words, the size of the cache in bytes is:

4 * IndexReader.MaxDoc * (# of different fields actually used to sort)

For string fields, the cache is larger: in addition to the above array, the value of every term in the field is kept in memory. If there are many unique terms in the field, this could be quite large.

Note that the size of the cache is not affected by how many fields are in the index and might be used to sort - only by the ones actually used to sort a result set.

Created: Feb 12, 2004 10:53:57 AM

@since lucene 1.4

Inheritance

object

Sort

Inherited Members

object.Equals(object, object)

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

Namespace: Lucene.Net.Search

Assembly: Lucene.Net.dll

Syntax

public class Sort

Constructors

Sort()

Sorts by computed relevance. This is the same sort criteria as calling Search(Query, int) without a sort criteria, only with slightly more overhead.

Declaration

public Sort()

Sort(SortField)

Sorts by the criteria in the given SortField.

Declaration

public Sort(SortField field)

Parameters

Type	Name	Description
SortField	field

Sort(params SortField[])

Sorts in succession by the criteria in each SortField.

Declaration

public Sort(params SortField[] fields)

Parameters

Type	Name	Description
SortField[]	fields

Fields

INDEXORDER

Represents sorting by index order.

Declaration

public static readonly Sort INDEXORDER

Field Value

Type	Description
Sort

RELEVANCE

Represents sorting by computed relevance. Using this sort criteria returns the same results as calling Search(Query, int)without a sort criteria, only with slightly more overhead.

Declaration

public static readonly Sort RELEVANCE

Field Value

Type	Description
Sort

Properties

NeedsScores

Returns true if the relevance score is needed to sort documents.

Declaration

public virtual bool NeedsScores { get; }

Property Value

Type	Description
bool

Methods

Equals(object)

Returns true if o is equal to this.

Declaration

public override bool Equals(object o)

Parameters

Type	Name	Description
object	o

Returns

Type	Description
bool

Overrides

object.Equals(object)

GetHashCode()

Returns a hash code value for this object.

Declaration

public override int GetHashCode()

Returns

Type	Description
int

Overrides

object.GetHashCode()

GetSort()

Representation of the sort criteria.

Declaration

public virtual SortField[] GetSort()

Returns

Type	Description
SortField[]	Array of SortField objects used in this sort criteria

Rewrite(IndexSearcher)

Rewrites the SortFields in this Sort, returning a new Sort if any of the fields changes during their rewriting.

Note

This API is experimental and might change in incompatible ways in the next release.

Declaration

public virtual Sort Rewrite(IndexSearcher searcher)

Parameters

Type	Name	Description
IndexSearcher	searcher	IndexSearcher to use in the rewriting

Returns

Type	Description
Sort	this if the Sort/Fields have not changed, or a new Sort if there is a change

Exceptions

Type	Condition
IOException	Can be thrown by the rewriting

SetSort(SortField)

Sets the sort to the given criteria.

NOTE: When overriding this method, be aware that the constructor of this class calls a private method and not this virtual method. So if you need to override the behavior during the initialization, call your own private method from the constructor with whatever custom behavior you need.

Declaration

public virtual void SetSort(SortField field)

Parameters

Type	Name	Description
SortField	field

SetSort(params SortField[])

Sets the sort to the given criteria in succession.

NOTE: When overriding this method, be aware that the constructor of this class calls a private method and not this virtual method. So if you need to override the behavior during the initialization, call your own private method from the constructor with whatever custom behavior you need.

Declaration

public virtual void SetSort(params SortField[] fields)

Parameters

Type	Name	Description
SortField[]	fields

ToString()

Returns a string that represents the current object.

Declaration

public override string ToString()

Returns

Type	Description
string	A string that represents the current object.

Overrides

object.ToString()