Package org.apache.lucene.util

Class OfflineSorter

java.lang.Object

org.apache.lucene.util.OfflineSorter

public class OfflineSorter
extends Object

On-disk sorting of byte arrays. Each byte array (entry) is a composed of the following fields:

• (two bytes) length of the following byte array,
• exactly the above count of bytes for the sequence to be sorted.

See Also:

• sort(String)

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

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static final class	OfflineSorter.BufferSize	A bit more descriptive unit for constructors.
static class	OfflineSorter.ByteSequencesReader	Utility class to read length-prefixed byte[] entries from an input.
static class	OfflineSorter.ByteSequencesWriter	Utility class to emit length-prefixed byte[] entries to an output stream for sorting.
class	OfflineSorter.SortInfo	Sort info (debugging mostly).

Field Summary

Fields

Modifier and Type	Field	Description
static final long	ABSOLUTE_MIN_SORT_BUFFER_SIZE	Absolute minimum required buffer size for sorting.
static final Comparator<BytesRef>	DEFAULT_COMPARATOR	Default comparator: sorts in binary (codepoint) order
static final long	GB	Convenience constant for gigabytes
static final int	MAX_TEMPFILES	Maximum number of temporary files before doing an intermediate merge.
static final long	MB	Convenience constant for megabytes
static final long	MIN_BUFFER_SIZE_MB	Minimum recommended buffer size for sorting.

Constructor Summary

Constructors

Constructor	Description
OfflineSorter(Directory dir, String tempFileNamePrefix)	Defaults constructor.
OfflineSorter(Directory dir, String tempFileNamePrefix, Comparator<BytesRef> comparator)	Defaults constructor with a custom comparator.
OfflineSorter(Directory dir, String tempFileNamePrefix, Comparator<BytesRef> comparator, OfflineSorter.BufferSize ramBufferSize, int maxTempfiles, int valueLength, ExecutorService exec, int maxPartitionsInRAM)	All-details constructor.

Method Summary

Modifier and Type	Method	Description
Comparator<BytesRef>	getComparator()	Returns the comparator in use to sort entries
Directory	getDirectory()	Returns the Directory we use to create temp files.
protected OfflineSorter.ByteSequencesReader	getReader(ChecksumIndexInput in, String name)	Subclasses can override to change how byte sequences are read from disk.
String	getTempFileNamePrefix()	Returns the temp file name prefix passed to Directory.createTempOutput(java.lang.String, java.lang.String, org.apache.lucene.store.IOContext) to generate temporary files.
protected OfflineSorter.ByteSequencesWriter	getWriter(IndexOutput out, long itemCount)	Subclasses can override to change how byte sequences are written to disk.
String	sort(String inputFileName)	Sort input to a new temp file, returning its name.

Methods inherited from class java.lang.Object

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

Field Details

MB

public static final long MB

Convenience constant for megabytes

See Also:

• Constant Field Values

GB

public static final long GB

Convenience constant for gigabytes

See Also:

• Constant Field Values

MIN_BUFFER_SIZE_MB

public static final long MIN_BUFFER_SIZE_MB

Minimum recommended buffer size for sorting.

See Also:

• Constant Field Values

ABSOLUTE_MIN_SORT_BUFFER_SIZE

public static final long ABSOLUTE_MIN_SORT_BUFFER_SIZE

Absolute minimum required buffer size for sorting.

See Also:

• Constant Field Values

MAX_TEMPFILES

public static final int MAX_TEMPFILES

Maximum number of temporary files before doing an intermediate merge.

See Also:

• Constant Field Values

DEFAULT_COMPARATOR

public static final Comparator<BytesRef> DEFAULT_COMPARATOR

Default comparator: sorts in binary (codepoint) order

Constructor Details

OfflineSorter

public OfflineSorter(Directory dir,
 String tempFileNamePrefix)
              throws IOException

Defaults constructor.

Throws:

IOException

See Also:

• OfflineSorter.BufferSize.automatic()

OfflineSorter

public OfflineSorter(Directory dir,
 String tempFileNamePrefix,
 Comparator<BytesRef> comparator)
              throws IOException

Defaults constructor with a custom comparator.

Throws:

IOException

See Also:

• OfflineSorter.BufferSize.automatic()

OfflineSorter

public OfflineSorter(Directory dir,
 String tempFileNamePrefix,
 Comparator<BytesRef> comparator,
 OfflineSorter.BufferSize ramBufferSize,
 int maxTempfiles,
 int valueLength,
 ExecutorService exec,
 int maxPartitionsInRAM)

All-details constructor. If valueLength is -1 (the default), the length of each value differs; otherwise, all values have the specified length. If you pass a non-null ExecutorService then it will be used to run sorting operations that can be run concurrently, and maxPartitionsInRAM is the maximum concurrent in-memory partitions. Thus the maximum possible RAM used by this class while sorting is maxPartitionsInRAM * ramBufferSize.

Method Details

getDirectory

public Directory getDirectory()

Returns the Directory we use to create temp files.

getTempFileNamePrefix

public String getTempFileNamePrefix()

Returns the temp file name prefix passed to Directory.createTempOutput(java.lang.String, java.lang.String, org.apache.lucene.store.IOContext) to generate temporary files.

sort

public String sort(String inputFileName)
            throws IOException

Sort input to a new temp file, returning its name.

Throws:

IOException

getWriter

protected OfflineSorter.ByteSequencesWriter getWriter(IndexOutput out,
 long itemCount)
                                               throws IOException

Subclasses can override to change how byte sequences are written to disk.

Throws:

IOException

getReader

protected OfflineSorter.ByteSequencesReader getReader(ChecksumIndexInput in,
 String name)
                                               throws IOException

Subclasses can override to change how byte sequences are read from disk.

Throws:

IOException

getComparator

public Comparator<BytesRef> getComparator()

Returns the comparator in use to sort entries