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, FilterNumFilteredFields, Footer
  • Filter --> FieldNumber, FuzzySet
  • FuzzySet -->See Serialize(DataOutput)
  • Header --> CodecHeader ()
  • DelegatePostingsFormatName --> String () The name of a ServiceProvider registered PostingsFormat
  • NumFilteredFields --> Uint32 ()
  • FieldNumber --> Uint32 () 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
Namespace: Lucene.Net.Codecs.Bloom
Assembly: Lucene.Net.Codecs.dll
Syntax
public sealed class BloomFilteringPostingsFormat : PostingsFormat

Constructors

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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()
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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.
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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

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VERSION_CHECKSUM

Declaration
public static readonly int VERSION_CHECKSUM
Field Value
Type Description
System.Int32
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VERSION_CURRENT

Declaration
public static readonly int VERSION_CURRENT
Field Value
Type Description
System.Int32
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VERSION_START

Declaration
public static readonly int VERSION_START
Field Value
Type Description
System.Int32

Methods

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FieldsConsumer(SegmentWriteState)

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

Declaration
public override FieldsProducer FieldsProducer(SegmentReadState state)
Parameters
Type Name Description
SegmentReadState state
Returns
Type Description
FieldsProducer
Overrides