Package org.apache.lucene.codecs

Class MultiLevelSkipListReader

java.lang.Object

org.apache.lucene.codecs.MultiLevelSkipListReader

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable

Direct Known Subclasses:

Lucene50SkipReader, Lucene84SkipReader, Lucene90SkipReader, SimpleTextSkipReader

public abstract class MultiLevelSkipListReader
extends java.lang.Object
implements java.io.Closeable

This abstract class reads skip lists with multiple levels.

See MultiLevelSkipListWriter for the information about the encoding of the multi level skip lists.

Subclasses must implement the abstract method readSkipData(int, IndexInput) which defines the actual format of the skip data.

Field Summary

Fields

Modifier and Type	Field	Description
private long[]	childPointer	Child pointer of current skip entry per level.
private int	docCount
private long	lastChildPointer	childPointer of last read skip entry with docId <= target.
private int	lastDoc	Doc id of last read skip entry with docId <= target.
protected int	maxNumberOfSkipLevels	the maximum number of skip levels possible for this index
protected int	numberOfSkipLevels	number of levels in this skip list
private int[]	numSkipped	Number of docs skipped per level.
protected int[]	skipDoc	Doc id of current skip entry per level.
private int[]	skipInterval	skipInterval of each level.
private int	skipMultiplier
private long[]	skipPointer	The start pointer of each skip level.
private IndexInput[]	skipStream	skipStream for each level.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	MultiLevelSkipListReader(IndexInput skipStream, int maxSkipLevels, int skipInterval)	Creates a MultiLevelSkipListReader, where skipInterval and skipMultiplier are the same.
protected	MultiLevelSkipListReader(IndexInput skipStream, int maxSkipLevels, int skipInterval, int skipMultiplier)	Creates a MultiLevelSkipListReader.

Method Summary

Modifier and Type	Method	Description
void	close()
int	getDoc()	Returns the id of the doc to which the last call of skipTo(int) has skipped.
void	init(long skipPointer, int df)	Initializes the reader, for reuse on a new term.
private boolean	loadNextSkip(int level)
private void	loadSkipLevels()	Loads the skip levels
protected long	readChildPointer(IndexInput skipStream)	read the child pointer written via MultiLevelSkipListWriter.writeChildPointer(long, DataOutput).
protected long	readLevelLength(IndexInput skipStream)	read the length of the current level written via MultiLevelSkipListWriter.writeLevelLength(long, IndexOutput).
protected abstract int	readSkipData(int level, IndexInput skipStream)	Subclasses must implement the actual skip data encoding in this method.
protected void	seekChild(int level)	Seeks the skip entry on the given level
protected void	setLastSkipData(int level)	Copies the values of the last read skip entry on this level
int	skipTo(int target)	Skips entries to the first beyond the current whose document number is greater than or equal to target.

Methods inherited from class java.lang.Object

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

Field Detail

maxNumberOfSkipLevels

protected int maxNumberOfSkipLevels

the maximum number of skip levels possible for this index

numberOfSkipLevels

protected int numberOfSkipLevels

number of levels in this skip list

docCount

private int docCount

skipStream

private IndexInput[] skipStream

skipStream for each level.

skipPointer

private long[] skipPointer

The start pointer of each skip level.

skipInterval

private int[] skipInterval

skipInterval of each level.

numSkipped

private int[] numSkipped

Number of docs skipped per level. It's possible for some values to overflow a signed int, but this has been accounted for.

skipDoc

protected int[] skipDoc

Doc id of current skip entry per level.

lastDoc

private int lastDoc

Doc id of last read skip entry with docId <= target.

childPointer

private long[] childPointer

Child pointer of current skip entry per level.

lastChildPointer

private long lastChildPointer

childPointer of last read skip entry with docId <= target.

skipMultiplier

private final int skipMultiplier

Constructor Detail

MultiLevelSkipListReader

protected MultiLevelSkipListReader(IndexInput skipStream,
                                   int maxSkipLevels,
                                   int skipInterval,
                                   int skipMultiplier)

Creates a MultiLevelSkipListReader.

MultiLevelSkipListReader

protected MultiLevelSkipListReader(IndexInput skipStream,
                                   int maxSkipLevels,
                                   int skipInterval)

Creates a MultiLevelSkipListReader, where skipInterval and skipMultiplier are the same.

Method Detail

getDoc

public int getDoc()

Returns the id of the doc to which the last call of skipTo(int) has skipped.

skipTo

public int skipTo(int target)
           throws java.io.IOException

Skips entries to the first beyond the current whose document number is greater than or equal to target. Returns the current doc count.

Throws:

java.io.IOException

loadNextSkip

private boolean loadNextSkip(int level)
                      throws java.io.IOException

Throws:

java.io.IOException

seekChild

protected void seekChild(int level)
                  throws java.io.IOException

Seeks the skip entry on the given level

Throws:

java.io.IOException

close

public void close()
           throws java.io.IOException

Specified by:

close in interface java.lang.AutoCloseable

Specified by:

close in interface java.io.Closeable

Throws:

java.io.IOException

init

public void init(long skipPointer,
                 int df)
          throws java.io.IOException

Initializes the reader, for reuse on a new term.

Throws:

java.io.IOException

loadSkipLevels

private void loadSkipLevels()
                     throws java.io.IOException

Loads the skip levels

Throws:

java.io.IOException

readSkipData

protected abstract int readSkipData(int level,
                                    IndexInput skipStream)
                             throws java.io.IOException

Subclasses must implement the actual skip data encoding in this method.

Parameters:

level - the level skip data shall be read from

skipStream - the skip stream to read from

Throws:

java.io.IOException

readLevelLength

protected long readLevelLength(IndexInput skipStream)
                        throws java.io.IOException

read the length of the current level written via MultiLevelSkipListWriter.writeLevelLength(long, IndexOutput).

Parameters:

skipStream - the IndexInput the length shall be read from

Returns:

level length

Throws:

java.io.IOException

readChildPointer

protected long readChildPointer(IndexInput skipStream)
                         throws java.io.IOException

read the child pointer written via MultiLevelSkipListWriter.writeChildPointer(long, DataOutput).

Parameters:

skipStream - the IndexInput the child pointer shall be read from

Returns:

child pointer

Throws:

java.io.IOException

setLastSkipData

protected void setLastSkipData(int level)

Copies the values of the last read skip entry on this level