Class DoubleField
Field that indexes System.Double values for efficient range filtering and sorting. Here's an example usage:
document.Add(new DoubleField(name, 6.0, Field.Store.NO));
For optimal performance, re-use the DoubleField and
Document instance for more than one document:
DoubleField field = new DoubleField(name, 0.0, Field.Store.NO);
Document document = new Document();
document.Add(field);
for (all documents)
{
...
field.SetDoubleValue(value)
writer.AddDocument(document);
...
}
See also Int32Field, Int64Field,
SingleField.
To perform range querying or filtering against a DoubleField, use NumericRangeQuery or NumericRangeFilter<T>. To sort according to a DoubleField, use the normal numeric sort types, eg DOUBLE. DoubleField values can also be loaded directly from IFieldCache.
You may add the same field name as an DoubleField 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 DoubleField.
A DoubleField 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 System.Int32.MaxValue, which produces one
term per value.
For more information on the internals of numeric trie
indexing, including the PrecisionStep (precisionStep
)
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 System.Int32.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.
@since 2.9
Inherited Members
Namespace: Lucene.Net.Documents
Assembly: Lucene.Net.dll
Syntax
public sealed class DoubleField : Field, IIndexableField, IFormattable
Constructors
| Improve this Doc View SourceDoubleField(String, Double, Field.Store)
Creates a stored or un-stored DoubleField with the provided value
and default precisionStep
PRECISION_STEP_DEFAULT (4).
Declaration
public DoubleField(string name, double value, Field.Store stored)
Parameters
Type | Name | Description |
---|---|---|
System.String | name | field name |
System.Double | value | 64-bit System.Double value |
Field.Store | stored | YES if the content should also be stored |
Exceptions
Type | Condition |
---|---|
System.ArgumentNullException | if the field name is |
DoubleField(String, Double, FieldType)
Expert: allows you to customize the FieldType.
Declaration
public DoubleField(string name, double value, FieldType type)
Parameters
Type | Name | Description |
---|---|---|
System.String | name | field name |
System.Double | value | 64-bit double value |
FieldType | type | customized field type: must have NumericType of DOUBLE. |
Exceptions
Type | Condition |
---|---|
System.ArgumentNullException | if the field name or type is |
Fields
| Improve this Doc View SourceTYPE_NOT_STORED
Type for a DoubleField 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 DoubleField: normalization factors, frequencies, and positions are omitted.
Declaration
public static readonly FieldType TYPE_STORED
Field Value
Type | Description |
---|---|
FieldType |