Class Lucene90BlockTreeTermsReader
java.lang.Object
org.apache.lucene.index.Fields
org.apache.lucene.codecs.FieldsProducer
org.apache.lucene.codecs.lucene90.blocktree.Lucene90BlockTreeTermsReader
- All Implemented Interfaces:
Closeable
,AutoCloseable
,Iterable<String>
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 its own fixed terms index (ie, it does not support a pluggable terms index
implementation).
NOTE: this terms dictionary supports min/maxItemsPerBlock during indexing to control how much memory the terms index uses.
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.
- WARNING: This API is experimental and might change in incompatible ways in the next release.
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Field Summary
FieldsModifier and TypeFieldDescriptionstatic final int
Current terms format.static final int
Initial terms format.Fields inherited from class org.apache.lucene.index.Fields
EMPTY_ARRAY
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Constructor Summary
ConstructorsConstructorDescriptionLucene90BlockTreeTermsReader
(PostingsReaderBase postingsReader, SegmentReadState state) Sole constructor. -
Method Summary
Methods inherited from class org.apache.lucene.codecs.FieldsProducer
getMergeInstance
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
Methods inherited from interface java.lang.Iterable
forEach, spliterator
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Field Details
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VERSION_START
public static final int VERSION_STARTInitial terms format.- See Also:
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VERSION_CURRENT
public static final int VERSION_CURRENTCurrent terms format.- See Also:
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Constructor Details
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Lucene90BlockTreeTermsReader
public Lucene90BlockTreeTermsReader(PostingsReaderBase postingsReader, SegmentReadState state) throws IOException Sole constructor.- Throws:
IOException
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Method Details
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close
- Specified by:
close
in interfaceAutoCloseable
- Specified by:
close
in interfaceCloseable
- Specified by:
close
in classFieldsProducer
- Throws:
IOException
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iterator
Description copied from class:Fields
Returns an iterator that will step through all fields names. This will not return null. -
terms
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. -
checkIntegrity
Description copied from class:FieldsProducer
Checks consistency of this reader.Note that this may be costly in terms of I/O, e.g. may involve computing a checksum value against large data files.
- Specified by:
checkIntegrity
in classFieldsProducer
- Throws:
IOException
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toString
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