Class PostingsFormat

Encodes/decodes terms, postings, and proximity data.

Note, when extending this class, the name (Name) may written into the index in certain configurations. In order for the segment to be read, the name must resolve to your implementation via ForName(String). This method uses GetPostingsFormat(String) to resolve format names.

If you implement your own format:

  1. Subclass this class.
  2. Subclass DefaultPostingsFormatFactory, override Initialize(), and add the line base.ScanForPostingsFormats(typeof(YourPostingsFormat).Assembly). If you have any format classes in your assembly that are not meant for reading, you can add the ExcludePostingsFormatFromScanAttribute to them so they are ignored by the scan.
  3. Set the new IPostingsFormatFactory by calling SetPostingsFormatFactory(IPostingsFormatFactory) at application startup.
If your format has dependencies, you may also override GetPostingsFormat(Type) to inject them via pure DI or a DI container. See DI-Friendly Framework to understand the approach used.

PostingsFormat Names

Unlike the Java version, format names are by default convention-based on the class name. If you name your custom format class "MyCustomPostingsFormat", the codec name will the same name without the "PostingsFormat" suffix: "MyCustom".

You can override this default behavior by using the PostingsFormatNameAttribute to name the format differently than this convention. Format names must be all ASCII alphanumeric, and less than 128 characters in length.

This is a Lucene.NET EXPERIMENTAL API, use at your own risk
Inheritance
System.Object
PostingsFormat
Lucene40PostingsFormat
Lucene41PostingsFormat
PerFieldPostingsFormat
Inherited Members
System.Object.Equals(System.Object)
System.Object.Equals(System.Object, System.Object)
System.Object.GetHashCode()
System.Object.GetType()
System.Object.MemberwiseClone()
System.Object.ReferenceEquals(System.Object, System.Object)
Namespace: Lucene.Net.Codecs
Assembly: Lucene.Net.dll
Syntax
public abstract class PostingsFormat

Constructors

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PostingsFormat()

Creates a new postings format.

The provided name will be written into the index segment in some configurations (such as when using PerFieldPostingsFormat): in such configurations, for the segment to be read this class should be registered by subclassing DefaultPostingsFormatFactory and calling ScanForPostingsFormats(Assembly) in the class constructor. The new IPostingsFormatFactory can be registered by calling SetPostingsFormatFactory(IPostingsFormatFactory) at application startup.

Declaration
protected PostingsFormat()

Fields

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EMPTY

Zero-length PostingsFormat array.

Declaration
public static readonly PostingsFormat[] EMPTY
Field Value
Type Description
PostingsFormat[]

Properties

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AvailablePostingsFormats

Returns a list of all available format names.

Declaration
public static ICollection<string> AvailablePostingsFormats { get; }
Property Value
Type Description
System.Collections.Generic.ICollection<System.String>
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Name

Returns this posting format's name.

Declaration
public string Name { get; }
Property Value
Type Description
System.String

Methods

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FieldsConsumer(SegmentWriteState)

Writes a new segment.

Declaration
public abstract FieldsConsumer FieldsConsumer(SegmentWriteState state)
Parameters
Type Name Description
SegmentWriteState state
Returns
Type Description
FieldsConsumer
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FieldsProducer(SegmentReadState)

Reads a segment. NOTE: by the time this call returns, it must hold open any files it will need to use; else, those files may be deleted. Additionally, required files may be deleted during the execution of this call before there is a chance to open them. Under these circumstances an System.IO.IOException should be thrown by the implementation. System.IO.IOExceptions are expected and will automatically cause a retry of the segment opening logic with the newly revised segments.

Declaration
public abstract FieldsProducer FieldsProducer(SegmentReadState state)
Parameters
Type Name Description
SegmentReadState state
Returns
Type Description
FieldsProducer
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ForName(String)

Looks up a format by name.

Declaration
public static PostingsFormat ForName(string name)
Parameters
Type Name Description
System.String name
Returns
Type Description
PostingsFormat
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GetPostingsFormatFactory()

Gets the associated PostingsFormat factory.

Declaration
public static IPostingsFormatFactory GetPostingsFormatFactory()
Returns
Type Description
IPostingsFormatFactory

The PostingsFormat factory.
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SetPostingsFormatFactory(IPostingsFormatFactory)

Sets the IPostingsFormatFactory instance used to instantiate PostingsFormat subclasses.

Declaration
public static void SetPostingsFormatFactory(IPostingsFormatFactory postingsFormatFactory)
Parameters
Type Name Description
IPostingsFormatFactory postingsFormatFactory

The new IPostingsFormatFactory.
Exceptions
Type Condition
System.ArgumentNullException

The postingsFormatFactory parameter is null.
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ToString()

Declaration
public override string ToString()
Returns
Type Description
System.String
Overrides
System.Object.ToString()

See Also