java.lang.Object
- org.apache.lucene.index.Fields
- - org.apache.lucene.codecs.FieldsProducer
  - - org.apache.lucene.codecs.blocktree.BlockTreeTermsReader

All Implemented Interfaces:

Closeable, AutoCloseable, Iterable<String>, Accountable
```
public final 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 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. See BlockTreeTermsWriter.

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

Field Summary

Fields
Modifier and Type	Field	Description
`static int`	`VERSION_COMPRESSED_SUFFIXES`	Suffixes are compressed to save space.
`static int`	`VERSION_CURRENT`	Current terms format.
`static int`	`VERSION_META_FILE`	Metadata is written to its own file.
`static int`	`VERSION_META_LONGS_REMOVED`	The long[] + byte[] metadata has been replaced with a single byte[].
`static int`	`VERSION_START`	Initial terms format.

Fields inherited from class org.apache.lucene.index.Fields
EMPTY_ARRAY

Constructor Summary

Constructors
Constructor Description

BlockTreeTermsReader(PostingsReaderBase postingsReader, SegmentReadState state)
Sole constructor.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`void`	`checkIntegrity()`	Checks consistency of this reader.
`void`	`close()`
`Collection<Accountable>`	`getChildResources()`	Returns nested resources of this class.
`Iterator<String>`	`iterator()`	Returns an iterator that will step through all fields names.
`long`	`ramBytesUsed()`	Return the memory usage of this object in bytes.
`int`	`size()`	Returns the number of fields or -1 if the number of distinct field names is unknown.
`Terms`	`terms(String field)`	Get the `Terms` for this field.
`String`	`toString()`

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

- Field Detail
  - VERSION_START
```
public static final int VERSION_START
```
    Initial terms format.
    
    See Also:
    
    Constant Field Values
  - VERSION_META_LONGS_REMOVED
```
public static final int VERSION_META_LONGS_REMOVED
```
    The long[] + byte[] metadata has been replaced with a single byte[].
    
    See Also:
    
    Constant Field Values
  - VERSION_COMPRESSED_SUFFIXES
```
public static final int VERSION_COMPRESSED_SUFFIXES
```
    Suffixes are compressed to save space.
    
    See Also:
    
    Constant Field Values
  - VERSION_META_FILE
```
public static final int VERSION_META_FILE
```
    Metadata is written to its own file.
    
    See Also:
    
    Constant Field Values
  - VERSION_CURRENT
```
public static final int VERSION_CURRENT
```
    Current terms format.
    
    See Also:
    
    Constant Field Values
- Constructor Detail
  - BlockTreeTermsReader
```
public BlockTreeTermsReader(PostingsReaderBase postingsReader,
                            SegmentReadState state)
                     throws IOException
```
    Sole constructor.
    
    Throws:
    
    IOException
- Method Detail
  - close
```
public void close()
           throws IOException
```
    Specified by:
    
    close in interface AutoCloseable
    
    Specified by:
    
    close in interface Closeable
    
    Specified by:
    
    close in class FieldsProducer
    
    Throws:
    
    IOException
  - 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.
    
    Specified by:
    
    iterator in interface Iterable<String>
    
    Specified by:
    
    iterator in class Fields
  - terms
```
public Terms terms(String field)
            throws IOException
```
    Description copied from class: Fields
    
    Get the Terms for this field. This will return null if the field does not exist.
    
    Specified by:
    
    terms in class Fields
    
    Throws:
    
    IOException
  - 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.
    
    Specified by:
    
    size in class Fields
  - ramBytesUsed
```
public long ramBytesUsed()
```
    Description copied from interface: Accountable
    
    Return the memory usage of this object in bytes. Negative values are illegal.
  - getChildResources
```
public Collection<Accountable> getChildResources()
```
    Description copied from interface: Accountable
    
    Returns nested resources of this class. The result should be a point-in-time snapshot (to avoid race conditions).
    
    See Also:
    
    Accountables
  - checkIntegrity
```
public void checkIntegrity()
                    throws IOException
```
    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 class FieldsProducer
    
    Throws:
    
    IOException
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object

Class BlockTreeTermsReader

Field Summary

Fields inherited from class org.apache.lucene.index.Fields

Constructor Summary

Method Summary

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

Methods inherited from class java.lang.Object

Methods inherited from interface java.lang.Iterable

Field Detail

VERSION_START

VERSION_META_LONGS_REMOVED

VERSION_COMPRESSED_SUFFIXES

VERSION_META_FILE

VERSION_CURRENT

Constructor Detail

BlockTreeTermsReader

Method Detail

close

iterator

terms

size

ramBytesUsed

getChildResources

checkIntegrity

toString