org.apache.hadoop.hbase.regionserver.wal

Class LRUDictionary

java.lang.Object

org.apache.hadoop.hbase.regionserver.wal.LRUDictionary

@InterfaceAudience.Private
public class LRUDictionary
extends Object

WALDictionary using an LRU eviction algorithm. Uses a linked list running through a hashtable. Currently has max of 2^15 entries. Will start evicting if exceeds this number The maximum memory we expect this dictionary to take in the worst case is about: (2 ^ 15) * 5 (Regionname, Row key, CF, Column qual, table) * 100 bytes (these are some big names) = ~16MB. If you want to get silly, even at 1kb entries, it maxes out at 160 megabytes.

Field Summary

Fields

Modifier and Type	Field and Description
static byte	NOT_IN_DICTIONARY

Constructor Summary

Constructors

Constructor and Description
LRUDictionary()

Method Summary

Methods

Modifier and Type	Method and Description
short	addEntry(byte[] data, int offset, int length) Adds an entry to the dictionary.
void	clear() Flushes the dictionary, empties all values.
short	findEntry(byte[] data, int offset, int length) Finds the index of an entry.
byte[]	getEntry(short idx) Gets an entry from the dictionary.
void	init(int initialSize)

Methods inherited from class java.lang.Object

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

Field Detail

NOT_IN_DICTIONARY

public static final byte NOT_IN_DICTIONARY

See Also:

Constant Field Values

Constructor Detail

LRUDictionary

public LRUDictionary()

Method Detail

getEntry

public byte[] getEntry(short idx)

Gets an entry from the dictionary.

Parameters:

idx - index of the entry

Returns:

the entry, or null if non existent

init

public void init(int initialSize)

findEntry

public short findEntry(byte[] data,
              int offset,
              int length)

Finds the index of an entry. If no entry found, we add it.

Parameters:

data - the byte array that we're looking up

offset - Offset into data to add to Dictionary.

length - Length beyond offset that comprises entry; must be > 0.

Returns:

the index of the entry, or NOT_IN_DICTIONARY if not found

addEntry

public short addEntry(byte[] data,
             int offset,
             int length)

Adds an entry to the dictionary. Be careful using this method. It will add an entry to the dictionary even if it already has an entry for the same data. Call {findEntry(byte[], int, int)} to add without duplicating dictionary entries.

Parameters:

data - the entry to add

offset - Offset into data to add to Dictionary.

length - Length beyond offset that comprises entry; must be > 0.

Returns:

the index of the entry

clear

public void clear()

Flushes the dictionary, empties all values.