Package org.apache.lucene.codecs
Class BlockTreeTermsReader
- java.lang.Object
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- org.apache.lucene.index.Fields
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- org.apache.lucene.codecs.FieldsProducer
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- org.apache.lucene.codecs.BlockTreeTermsReader
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- All Implemented Interfaces:
Closeable
,AutoCloseable
,Iterable<String>
public class BlockTreeTermsReader extends FieldsProducer
A block-based terms index and dictionary that assigns terms to variable length blocks according to how they share prefixes. The terms index is a prefix trie whose leaves are term blocks. The advantage of this approach is that seekExact is often able to determine a term cannot exist without doing any IO, and intersection with Automata is very fast. Note that this terms dictionary has it's own fixed terms index (ie, it does not support a pluggable terms index implementation).NOTE: this terms dictionary does not support index divisor when opening an IndexReader. Instead, you can change the min/maxItemsPerBlock during indexing.
The data structure used by this implementation is very similar to a burst trie (http://citeseer.ist.psu.edu/viewdoc/summary?doi=10.1.1.18.3499), but with added logic to break up too-large blocks of all terms sharing a given prefix into smaller ones.
Use
CheckIndex
with the-verbose
option to see summary statistics on the blocks in the dictionary. SeeBlockTreeTermsWriter
.
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Nested Class Summary
Nested Classes Modifier and Type Class Description class
BlockTreeTermsReader.FieldReader
BlockTree's implementation ofTerms
.static class
BlockTreeTermsReader.Stats
BlockTree statistics for a single field returned byBlockTreeTermsReader.FieldReader.computeStats()
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Field Summary
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Fields inherited from class org.apache.lucene.index.Fields
EMPTY_ARRAY
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Constructor Summary
Constructors Constructor Description BlockTreeTermsReader(Directory dir, FieldInfos fieldInfos, SegmentInfo info, PostingsReaderBase postingsReader, IOContext ioContext, String segmentSuffix, int indexDivisor)
Sole constructor.
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description void
close()
Iterator<String>
iterator()
Returns an iterator that will step through all fields names.long
ramBytesUsed()
Returns approximate RAM bytes usedint
size()
Returns the number of fields or -1 if the number of distinct field names is unknown.Terms
terms(String field)
Get theTerms
for this field.-
Methods inherited from class org.apache.lucene.index.Fields
getUniqueTermCount
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Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
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Methods inherited from interface java.lang.Iterable
forEach, spliterator
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Constructor Detail
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BlockTreeTermsReader
public BlockTreeTermsReader(Directory dir, FieldInfos fieldInfos, SegmentInfo info, PostingsReaderBase postingsReader, IOContext ioContext, String segmentSuffix, int indexDivisor) throws IOException
Sole constructor.- Throws:
IOException
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Method Detail
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close
public void close() throws IOException
- Specified by:
close
in interfaceAutoCloseable
- Specified by:
close
in interfaceCloseable
- Specified by:
close
in classFieldsProducer
- Throws:
IOException
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iterator
public Iterator<String> iterator()
Description copied from class:Fields
Returns an iterator that will step through all fields names. This will not return null.
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terms
public Terms terms(String field) throws IOException
Description copied from class:Fields
Get theTerms
for this field. This will return null if the field does not exist.- Specified by:
terms
in classFields
- Throws:
IOException
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size
public int size()
Description copied from class:Fields
Returns the number of fields or -1 if the number of distinct field names is unknown. If >= 0,Fields.iterator()
will return as many field names.
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ramBytesUsed
public long ramBytesUsed()
Description copied from class:FieldsProducer
Returns approximate RAM bytes used- Specified by:
ramBytesUsed
in classFieldsProducer
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