public final class FloatField extends Field
Field that indexes float values
for efficient range filtering and sorting. Here's an example usage:
document.add(new FloatField(name, 6.0F, Field.Store.NO));For optimal performance, re-use the
FloatField and
Document instance for more than one document:
FloatField field = new FloatField(name, 0.0F, Field.Store.NO);
Document document = new Document();
document.add(field);
for(all documents) {
...
field.setFloatValue(value)
writer.addDocument(document);
...
}
See also IntField, LongField, DoubleField.
To perform range querying or filtering against a
FloatField, use NumericRangeQuery or NumericRangeFilter. To sort according to a
FloatField, use the normal numeric sort types, eg
SortField.Type.FLOAT. FloatField
values can also be loaded directly from FieldCache.
You may add the same field name as an FloatField 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 FloatField.
A FloatField 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 FieldType.setNumericPrecisionStep(int) method if you'd
like to change the value. Note that you must also
specify a congruent value when creating NumericRangeQuery or NumericRangeFilter.
For low cardinality fields larger precision steps are good.
If the cardinality is < 100, it is fair
to use Integer.MAX_VALUE, which produces one
term per value.
For more information on the internals of numeric trie
indexing, including the precisionStep
configuration, see NumericRangeQuery. 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 Integer.MAX_VALUE.
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.
Field.Index, Field.Store, Field.TermVector| Modifier and Type | Field and Description |
|---|---|
static FieldType |
TYPE_NOT_STORED
Type for a FloatField that is not stored:
normalization factors, frequencies, and positions are omitted.
|
static FieldType |
TYPE_STORED
Type for a stored FloatField:
normalization factors, frequencies, and positions are omitted.
|
boost, fieldsData, name, tokenStream, type| Constructor and Description |
|---|
FloatField(String name,
float value,
Field.Store stored)
Creates a stored or un-stored FloatField with the provided value
and default
precisionStep NumericUtils.PRECISION_STEP_DEFAULT (4). |
FloatField(String name,
float value,
FieldType type)
Expert: allows you to customize the
FieldType. |
binaryValue, boost, fieldType, name, numericValue, readerValue, setBoost, setBytesValue, setBytesValue, setByteValue, setDoubleValue, setFloatValue, setIntValue, setLongValue, setReaderValue, setShortValue, setStringValue, setTokenStream, stringValue, tokenStream, tokenStreamValue, toString, translateFieldTypepublic static final FieldType TYPE_NOT_STORED
public static final FieldType TYPE_STORED
public FloatField(String name, float value, Field.Store stored)
precisionStep NumericUtils.PRECISION_STEP_DEFAULT (4).name - field namevalue - 32-bit double valuestored - Store.YES if the content should also be storedIllegalArgumentException - if the field name is null.public FloatField(String name, float value, FieldType type)
FieldType.name - field namevalue - 32-bit float valuetype - customized field type: must have FieldType.numericType()
of FieldType.NumericType.FLOAT.IllegalArgumentException - if the field name or type is null, or
if the field type does not have a FLOAT numericType()Copyright © 2000-2012 Apache Software Foundation. All Rights Reserved.