Class SingleField

Field that indexes float values for efficient range filtering and sorting. Here's an example usage: 

document.Add(new SingleField(name, 6.0F, Field.Store.NO));

For optimal performance, re-use the SingleField and Document instance for more than one document:

FloatField field = new SingleField(name, 0.0F, Field.Store.NO);
 Document document = new Document();
 document.Add(field);

 for (all documents) 
 {
     ...
     field.SetSingleValue(value)
     writer.AddDocument(document);
     ...
 }

See also Int32Field, Int64Field, DoubleField.

To perform range querying or filtering against a SingleField, use NumericRangeQuery<T> or NumericRangeFilter<T>. To sort according to a SingleField, use the normal numeric sort types, eg SINGLE. SingleField values can also be loaded directly from IFieldCache.

You may add the same field name as an SingleField to the same document more than once. Range querying and filtering will be the logical OR of all values; so a range query will hit all documents that have at least one value in the range. However sort behavior is not defined. If you need to sort, you should separately index a single-valued SingleField.

A SingleField will consume somewhat more disk space in the index than an ordinary single-valued field. However, for a typical index that includes substantial textual content per document, this increase will likely be in the noise.

Within Lucene, each numeric value is indexed as a trie structure, where each term is logically assigned to larger and larger pre-defined brackets (which are simply lower-precision representations of the value). The step size between each successive bracket is called the precisionStep, measured in bits. Smaller precisionStep values result in larger number of brackets, which consumes more disk space in the index but may result in faster range search performance. The default value, 4, was selected for a reasonable tradeoff of disk space consumption versus performance. You can create a custom FieldType and invoke the NumericPrecisionStep setter if you'd like to change the value. Note that you must also specify a congruent value when creating NumericRangeQuery<T> or NumericRangeFilter<T>. For low cardinality fields larger precision steps are good. If the cardinality is < 100, it is fair to use MaxValue, which produces one term per value.

For more information on the internals of numeric trie indexing, including the PrecisionStepprecisionStep configuration, see NumericRangeQuery<T>. The format of indexed values is described in NumericUtils.

If you only need to sort by numeric value, and never run range querying/filtering, you can index using a precisionStep of MaxValue. this will minimize disk space consumed.

More advanced users can instead use NumericTokenStream directly, when indexing numbers. This class is a wrapper around this token stream type for easier, more intuitive usage.

NOTE: This was FloatField in Lucene

@since 2.9
Inheritance
object
Field
SingleField
Inherited Members
Namespace: Lucene.Net.Documents
Assembly: Lucene.Net.dll
Syntax
public sealed class SingleField : Field, IIndexableField, IFormattable

Constructors

SingleField(string, float, Store)

Creates a stored or un-stored SingleField with the provided value and default precisionStepPRECISION_STEP_DEFAULT (4).

Declaration
public SingleField(string name, float value, Field.Store stored)
Parameters
Type Name Description
string name

field name
float value

32-bit float value
Field.Store stored

YES if the content should also be stored
Exceptions
Type Condition
ArgumentNullException

if the field name is null.

SingleField(string, float, FieldType)

Expert: allows you to customize the FieldType.

Declaration
public SingleField(string name, float value, FieldType type)
Parameters
Type Name Description
string name

field name
float value

32-bit float value
FieldType type

customized field type: must have NumericType of SINGLE.
Exceptions
Type Condition
ArgumentNullException

if the field name or type is null.
ArgumentException

if the field type does not have a SINGLENumericType

Fields

TYPE_NOT_STORED

Type for a SingleField that is not stored: normalization factors, frequencies, and positions are omitted.

Declaration
public static readonly FieldType TYPE_NOT_STORED
Field Value
Type Description
FieldType

TYPE_STORED

Type for a stored SingleField: normalization factors, frequencies, and positions are omitted.

Declaration
public static readonly FieldType TYPE_STORED
Field Value
Type Description
FieldType

Implements

Extension Methods