Package org.apache.lucene.backward_codecs.lucene40.blocktree

# Class Lucene40BlockTreeTermsReader

java.lang.Object
org.apache.lucene.index.Fields
org.apache.lucene.codecs.FieldsProducer
org.apache.lucene.backward_codecs.lucene40.blocktree.Lucene40BlockTreeTermsReader

All Implemented Interfaces:
  `Closeable`, `AutoCloseable`, `Iterable<String>`

public final class Lucene40BlockTreeTermsReader 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 final int`
  `VERSION_COMPRESSED_SUFFIXES`
  Suffixes are compressed to save space.
  `static final int`
  `VERSION_CURRENT`
  Current terms format.
  `static final int`
  `VERSION_META_FILE`
  Metadata is written to its own file.
  `static final int`
  `VERSION_META_LONGS_REMOVED`
  The long[] + byte[] metadata has been replaced with a single byte[].
  `static final int`
  `VERSION_START`
  Initial terms format.

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

  `EMPTY_ARRAY`

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `Lucene40BlockTreeTermsReader(PostingsReaderBase postingsReader, SegmentReadState state)`
  Sole constructor.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `checkIntegrity()`
  `void`
  `close()`
  `Iterator<String>`
  `iterator()`
  `int`
  `size()`
  `Terms`
  `terms(String 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 Details

  - ### 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 Details

  - ### Lucene40BlockTreeTermsReader

    public Lucene40BlockTreeTermsReader(PostingsReaderBase postingsReader, SegmentReadState state) throws IOException
    Sole constructor.
    Throws:
      `IOException`

- ## Method Details

  - ### 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()
    Specified by:
      `iterator` in interface `Iterable<String>`
    Specified by:
      `iterator` in class `Fields`

  - ### terms

    public Terms terms(String field) throws IOException
    Specified by:
      `terms` in class `Fields`
    Throws:
      `IOException`

  - ### size

    public int size()
    Specified by:
      `size` in class `Fields`

  - ### checkIntegrity

    public void checkIntegrity() throws IOException
    Specified by:
      `checkIntegrity` in class `FieldsProducer`
    Throws:
      `IOException`

  - ### toString

    public String toString()
    Overrides:
      `toString` in class `Object`