org.apache.lucene.codecs.uniformsplit

Class FSTDictionary

java.lang.Object

org.apache.lucene.codecs.uniformsplit.FSTDictionary

All Implemented Interfaces:

IndexDictionary, Accountable

public class FSTDictionary
extends Object
implements IndexDictionary

Immutable stateless FST-based index dictionary kept in memory.

Use IndexDictionary.Builder to build the IndexDictionary.

Create a stateful IndexDictionary.Browser to seek a term in this IndexDictionary and get its corresponding block file pointer to the terms block file.

Its greatest advantage is to be very compact in memory thanks to both the compaction of the FST as a byte array, and the incremental encoding of the leaves block pointer values, which are long integers in increasing order, with PositiveIntOutputs.
With a compact dictionary in memory we can increase the number of blocks. This allows us to reduce the average block size, which means faster scan inside a block.

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

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
protected class	FSTDictionary.Browser Stateful FSTDictionary.Browser to seek a term in this FSTDictionary and get its corresponding block file pointer in the block file.
static class	FSTDictionary.BrowserSupplier Provides stateful FSTDictionary.Browser to seek in the FSTDictionary.
static class	FSTDictionary.Builder Builds an immutable FSTDictionary.

Field Summary

Fields

Modifier and Type	Field and Description
protected FST<Long>	dictionary

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	FSTDictionary(FST<Long> dictionary)

Method Summary

Modifier and Type	Method and Description
FSTDictionary.Browser	browser() Creates a new IndexDictionary.Browser.
long	ramBytesUsed()
protected static FSTDictionary	read(DataInput input, BlockDecoder blockDecoder) Reads a FSTDictionary from the provided input.
void	write(DataOutput output, BlockEncoder blockEncoder) Writes this dictionary to the provided output.

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.lucene.util.Accountable

getChildResources

Field Detail

dictionary

protected final FST<Long> dictionary

Constructor Detail

FSTDictionary

protected FSTDictionary(FST<Long> dictionary)

Method Detail

ramBytesUsed

public long ramBytesUsed()

Specified by:

ramBytesUsed in interface Accountable

write

public void write(DataOutput output,
                  BlockEncoder blockEncoder)
           throws IOException

Description copied from interface: IndexDictionary

Writes this dictionary to the provided output.

Specified by:

write in interface IndexDictionary

blockEncoder - The BlockEncoder for specific encoding of this index dictionary; or null if none.

Throws:

IOException

read

protected static FSTDictionary read(DataInput input,
                                    BlockDecoder blockDecoder)
                             throws IOException

Reads a FSTDictionary from the provided input.

Parameters:

blockDecoder - The BlockDecoder to use for specific decoding; or null if none.

Throws:

IOException

browser

public FSTDictionary.Browser browser()

Description copied from interface: IndexDictionary

Creates a new IndexDictionary.Browser.

Specified by:

browser in interface IndexDictionary