Expert: A base class for ValueSource implementations that retrieve values for a single field from the {@link Lucene.Net.Search.FieldCache FieldCache}.

Fields used herein nust be indexed (doesn't matter if these fields are stored or not).

It is assumed that each such indexed field is untokenized, or at least has a single token in a document. For documents with multiple tokens of the same field, behavior is undefined (It is likely that current code would use the value of one of these tokens, but this is not guaranteed).

Document with no tokens in this field are assigned the

CopyC#
Zero
value.

WARNING: The status of the Search.Function package is experimental. The APIs introduced here might change in the future and will not be supported anymore in such a case.

NOTE: with the switch in 2.9 to segment-based searching, if {@link #getValues} is invoked with a composite (multi-segment) reader, this can easily cause double RAM usage for the values in the FieldCache. It's best to switch your application to pass only atomic (single segment) readers to this API. Alternatively, for a short-term fix, you could wrap your ValueSource using {@link MultiValueSource}, which costs more CPU per lookup but will not consume double the FieldCache RAM.

Namespace: Lucene.Net.Search.Function
Assembly: Lucene.Net (in Lucene.Net.dll) Version: 2.9.4.1

Syntax

C#
[SerializableAttribute]
public abstract class FieldCacheSource : ValueSource
Visual Basic
<SerializableAttribute> _
Public MustInherit Class FieldCacheSource _
	Inherits ValueSource
Visual C++
[SerializableAttribute]
public ref class FieldCacheSource abstract : public ValueSource

Inheritance Hierarchy

See Also