Class BloomFilteringPostingsFormat

A PostingsFormat useful for low doc-frequency fields such as primary keys. Bloom filters are maintained in a ".blm" file which offers "fast-fail" for reads in segments known to have no record of the key. A choice of delegate PostingsFormat is used to record all other Postings data.

A choice of BloomFilterFactory can be passed to tailor Bloom Filter settings on a per-field basis. The default configuration is DefaultBloomFilterFactory which allocates a ~8mb bitset and hashes values using MurmurHash2. This should be suitable for most purposes.

The format of the blm file is as follows:

• BloomFilter (.blm) --> Header, DelegatePostingsFormatName, NumFilteredFields, Filter^{NumFilteredFields}, Footer
• Filter --> FieldNumber, FuzzySet
• FuzzySet -->See Serialize(DataOutput)
• Header --> CodecHeader (WriteHeader(DataOutput, String, Int32))
• DelegatePostingsFormatName --> String (WriteString(String)) The name of a ServiceProvider registered PostingsFormat
• NumFilteredFields --> Uint32 (WriteInt32(Int32))
• FieldNumber --> Uint32 (WriteInt32(Int32)) The number of the field in this segment
• Footer --> CodecFooter (WriteFooter(IndexOutput))

This is a Lucene.NET EXPERIMENTAL API, use at your own risk

Inheritance

System.Object

PostingsFormat

BloomFilteringPostingsFormat

Inherited Members

PostingsFormat.EMPTY

PostingsFormat.SetPostingsFormatFactory(IPostingsFormatFactory)

PostingsFormat.GetPostingsFormatFactory()

PostingsFormat.Name

PostingsFormat.ToString()

PostingsFormat.ForName(String)

PostingsFormat.AvailablePostingsFormats

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.Bloom

Assembly: Lucene.Net.Codecs.dll

Syntax

[PostingsFormatName("BloomFilter")]
public sealed class BloomFilteringPostingsFormat : PostingsFormat

Constructors

BloomFilteringPostingsFormat()

Used only by core Lucene at read-time via Service Provider instantiation - do not use at Write-time in application code.

Declaration

public BloomFilteringPostingsFormat()

BloomFilteringPostingsFormat(PostingsFormat)

Creates Bloom filters for a selection of fields created in the index. This is recorded as a set of Bitsets held as a segment summary in an additional "blm" file. This PostingsFormat delegates to a choice of delegate PostingsFormat for encoding all other postings data. This choice of constructor defaults to the DefaultBloomFilterFactory for configuring per-field BloomFilters.

Declaration

public BloomFilteringPostingsFormat(PostingsFormat delegatePostingsFormat)

Parameters

Type	Name	Description
PostingsFormat	delegatePostingsFormat	The PostingsFormat that records all the non-bloom filter data i.e. postings info.

BloomFilteringPostingsFormat(PostingsFormat, BloomFilterFactory)

Creates Bloom filters for a selection of fields created in the index. This is recorded as a set of Bitsets held as a segment summary in an additional "blm" file. This PostingsFormat delegates to a choice of delegate PostingsFormat for encoding all other postings data.

Declaration

public BloomFilteringPostingsFormat(PostingsFormat delegatePostingsFormat, BloomFilterFactory bloomFilterFactory)

Parameters

Type	Name	Description
PostingsFormat	delegatePostingsFormat	The PostingsFormat that records all the non-bloom filter data i.e. postings info.
BloomFilterFactory	bloomFilterFactory	The BloomFilterFactory responsible for sizing BloomFilters appropriately.

Fields

VERSION_CHECKSUM

Declaration

public static readonly int VERSION_CHECKSUM

Field Value

Type	Description
System.Int32

VERSION_CURRENT

Declaration

public static readonly int VERSION_CURRENT

Field Value

Type	Description
System.Int32

VERSION_START

Declaration

public static readonly int VERSION_START

Field Value

Type	Description
System.Int32

Methods

FieldsConsumer(SegmentWriteState)

Declaration

public override FieldsConsumer FieldsConsumer(SegmentWriteState state)

Parameters

Type	Name	Description
SegmentWriteState	state

Returns

Type	Description
FieldsConsumer

Overrides

PostingsFormat.FieldsConsumer(SegmentWriteState)

FieldsProducer(SegmentReadState)

Declaration

public override FieldsProducer FieldsProducer(SegmentReadState state)

Parameters

Type	Name	Description
SegmentReadState	state

Returns

Type	Description
FieldsProducer

Overrides

PostingsFormat.FieldsProducer(SegmentReadState)