Package org.apache.lucene.codecs.bloom

Class BloomFilteringPostingsFormat

java.lang.Object

org.apache.lucene.codecs.PostingsFormat

org.apache.lucene.codecs.bloom.BloomFilteringPostingsFormat

All Implemented Interfaces:

NamedSPILoader.NamedSPI

public final class BloomFilteringPostingsFormat
extends PostingsFormat

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 FuzzySet.serialize(DataOutput)
• Header --> IndexHeader
• DelegatePostingsFormatName --> String The name of a ServiceProvider registered PostingsFormat
• NumFilteredFields --> Uint32
• FieldNumber --> Uint32 The number of the field in this segment
• Footer --> CodecFooter

WARNING: This API is experimental and might change in incompatible ways in the next release.

Field Summary

Fields

Modifier and Type	Field	Description
static final String	BLOOM_CODEC_NAME
static final int	VERSION_CURRENT
static final int	VERSION_START

Fields inherited from class org.apache.lucene.codecs.PostingsFormat

EMPTY

Constructor Summary

Constructors

Constructor	Description
BloomFilteringPostingsFormat()
BloomFilteringPostingsFormat(PostingsFormat delegatePostingsFormat)	Creates Bloom filters for a selection of fields created in the index.
BloomFilteringPostingsFormat(PostingsFormat delegatePostingsFormat, BloomFilterFactory bloomFilterFactory)	Creates Bloom filters for a selection of fields created in the index.

Method Summary

Modifier and Type	Method	Description
FieldsConsumer	fieldsConsumer(SegmentWriteState state)
FieldsProducer	fieldsProducer(SegmentReadState state)
String	toString()

Methods inherited from class org.apache.lucene.codecs.PostingsFormat

availablePostingsFormats, forName, getName, reloadPostingsFormats

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Details

BLOOM_CODEC_NAME

public static final String BLOOM_CODEC_NAME

See Also:

• Constant Field Values

VERSION_START

public static final int VERSION_START

See Also:

• Constant Field Values

VERSION_CURRENT

public static final int VERSION_CURRENT

See Also:

• Constant Field Values

Constructor Details

BloomFilteringPostingsFormat

public BloomFilteringPostingsFormat(PostingsFormat delegatePostingsFormat,
 BloomFilterFactory 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.

Parameters:

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

bloomFilterFactory - The BloomFilterFactory responsible for sizing BloomFilters appropriately

BloomFilteringPostingsFormat

public BloomFilteringPostingsFormat(PostingsFormat delegatePostingsFormat)

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.

Parameters:

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

BloomFilteringPostingsFormat

public BloomFilteringPostingsFormat()

Method Details

fieldsConsumer

public FieldsConsumer fieldsConsumer(SegmentWriteState state)
                              throws IOException

Specified by:

fieldsConsumer in class PostingsFormat

Throws:

IOException

fieldsProducer

public FieldsProducer fieldsProducer(SegmentReadState state)
                              throws IOException

Specified by:

fieldsProducer in class PostingsFormat

Throws:

IOException

toString

public String toString()

Overrides:

toString in class PostingsFormat