Class FilteringTokenFilter

Abstract base class for TokenFilters that may remove tokens. You have to implement Accept() and return a boolean if the current token should be preserved. IncrementToken() uses this method to decide if a token should be passed to the caller.

As of Lucene 4.4, an ArgumentException is thrown when trying to disable position increments when filtering terms.

Inheritance

object

AttributeSource

TokenStream

TokenFilter

FilteringTokenFilter

StopFilter

TypeTokenFilter

CodepointCountFilter

KeepWordFilter

LengthFilter

Implements

IDisposable

Inherited Members

TokenFilter.m_input

TokenFilter.Dispose(bool)

TokenStream.Dispose()

AttributeSource.GetAttributeFactory()

AttributeSource.GetAttributeClassesEnumerator()

AttributeSource.GetAttributeImplsEnumerator()

AttributeSource.AddAttributeImpl(Attribute)

AttributeSource.AddAttribute<T>()

AttributeSource.HasAttributes

AttributeSource.HasAttribute<T>()

AttributeSource.GetAttribute<T>()

AttributeSource.ClearAttributes()

AttributeSource.CaptureState()

AttributeSource.RestoreState(AttributeSource.State)

AttributeSource.GetHashCode()

AttributeSource.Equals(object)

AttributeSource.ReflectAsString(bool)

AttributeSource.ReflectWith(IAttributeReflector)

AttributeSource.CloneAttributes()

AttributeSource.CopyTo(AttributeSource)

AttributeSource.ToString()

object.Equals(object, object)

object.GetType()

object.MemberwiseClone()

object.ReferenceEquals(object, object)

Namespace: Lucene.Net.Analysis.Util

Assembly: Lucene.Net.Analysis.Common.dll

Syntax

public abstract class FilteringTokenFilter : TokenFilter, IDisposable

Constructors

FilteringTokenFilter(LuceneVersion, TokenStream)

Create a new FilteringTokenFilter.

Declaration

public FilteringTokenFilter(LuceneVersion version, TokenStream @in)

Parameters

Type	Name	Description
LuceneVersion	version	the Lucene match version
TokenStream	in	the Lucene.Net.Analysis.TokenStream to consume

FilteringTokenFilter(LuceneVersion, bool, TokenStream)

Create a new FilteringTokenFilter.

Declaration

[Obsolete("enablePositionIncrements=false is not supported anymore as of Lucene 4.4")]
public FilteringTokenFilter(LuceneVersion version, bool enablePositionIncrements, TokenStream input)

Parameters

Type	Name	Description
LuceneVersion	version	the Lucene match version
bool	enablePositionIncrements	whether to increment position increments when filtering out terms
TokenStream	input	the input to consume

Fields

m_version

Abstract base class for TokenFilters that may remove tokens. You have to implement Accept() and return a boolean if the current token should be preserved. IncrementToken() uses this method to decide if a token should be passed to the caller.

As of Lucene 4.4, an ArgumentException is thrown when trying to disable position increments when filtering terms.

Declaration

protected readonly LuceneVersion m_version

Field Value

Type	Description
LuceneVersion

Properties

EnablePositionIncrements

Abstract base class for TokenFilters that may remove tokens. You have to implement Accept() and return a boolean if the current token should be preserved. IncrementToken() uses this method to decide if a token should be passed to the caller.

As of Lucene 4.4, an ArgumentException is thrown when trying to disable position increments when filtering terms.

Declaration

public virtual bool EnablePositionIncrements { get; }

Property Value

Type	Description
bool

Methods

Accept()

Override this method and return if the current input token should be returned by IncrementToken().

Declaration

protected abstract bool Accept()

Returns

Type	Description
bool

End()

This method is called by the consumer after the last token has been consumed, after Lucene.Net.Analysis.TokenStream.IncrementToken() returned false (using the new Lucene.Net.Analysis.TokenStream API). Streams implementing the old API should upgrade to use this feature.

This method can be used to perform any end-of-stream operations, such as setting the final offset of a stream. The final offset of a stream might differ from the offset of the last token eg in case one or more whitespaces followed after the last token, but a WhitespaceTokenizer was used.

Additionally any skipped positions (such as those removed by a stopfilter) can be applied to the position increment, or any adjustment of other attributes where the end-of-stream value may be important.

NOTE: The default implementation chains the call to the input TokenStream, so be sure to call base.End() first when overriding this method.

Declaration

public override void End()

Overrides

Lucene.Net.Analysis.TokenFilter.End()

Exceptions

Type	Condition
IOException	If an I/O error occurs

IncrementToken()

Consumers (i.e., Lucene.Net.Index.IndexWriter) use this method to advance the stream to the next token. Implementing classes must implement this method and update the appropriate Lucene.Net.Util.IAttributes with the attributes of the next token.

The producer must make no assumptions about the attributes after the method has been returned: the caller may arbitrarily change it. If the producer needs to preserve the state for subsequent calls, it can use Lucene.Net.Util.AttributeSource.CaptureState() to create a copy of the current attribute state.

this method is called for every token of a document, so an efficient implementation is crucial for good performance. To avoid calls to Lucene.Net.Util.AttributeSource.AddAttribute<T>() and Lucene.Net.Util.AttributeSource.GetAttribute<T>(), references to all Lucene.Net.Util.IAttributes that this stream uses should be retrieved during instantiation.

To ensure that filters and consumers know which attributes are available, the attributes must be added during instantiation. Filters and consumers are not required to check for availability of attributes in Lucene.Net.Analysis.TokenStream.IncrementToken().

Declaration

public override sealed bool IncrementToken()

Returns

Type	Description
bool	false for end of stream; true otherwise

Overrides

Lucene.Net.Analysis.TokenStream.IncrementToken()

Reset()

This method is called by a consumer before it begins consumption using Lucene.Net.Analysis.TokenStream.IncrementToken().

Resets this stream to a clean state. Stateful implementations must implement this method so that they can be reused, just as if they had been created fresh.

If you override this method, always call base.Reset(), otherwise some internal state will not be correctly reset (e.g., Lucene.Net.Analysis.Tokenizer will throw InvalidOperationException on further usage).

Declaration

public override void Reset()

Overrides

Lucene.Net.Analysis.TokenFilter.Reset()

Remarks

NOTE: The default implementation chains the call to the input Lucene.Net.Analysis.TokenStream, so be sure to call base.Reset() when overriding this method.

SetEnablePositionIncrements(bool)

If true, this Lucene.Net.Analysis.TokenFilter will preserve positions of the incoming tokens (ie, accumulate and set position increments of the removed tokens). Generally, true is best as it does not lose information (positions of the original tokens) during indexing.

When set, when a token is stopped (omitted), the position increment of the following token is incremented.

Declaration

[Obsolete("enablePositionIncrements=false is not supported anymore as of Lucene 4.4")]
public virtual void SetEnablePositionIncrements(bool enable)

Parameters

Type	Name	Description
bool	enable

Implements

IDisposable