Package edu.caltech.nanodb.storage.writeahead

Class LogSequenceNumber

java.lang.Object

edu.caltech.nanodb.storage.writeahead.LogSequenceNumber

All Implemented Interfaces:

java.lang.Cloneable, java.lang.Comparable<LogSequenceNumber>

public class LogSequenceNumber
extends java.lang.Object
implements java.lang.Comparable<LogSequenceNumber>, java.lang.Cloneable

This class represents a Log Sequence Number (LSN) in the write-ahead log. Every log record has a unique LSN value; furthermore, the LSN identifies the exact location of the log record on disk as well. Log Sequence Numbers are comprised of the following parts:

• The file number of the write-ahead log file for the record (range: 00000..65535)
• The offset of the log record from the start of the file (range: 0..2³¹-1)

This class is immutable so that it can be used in multithreaded code more easily.

Field Summary

Fields

Modifier and Type	Field	Description
private int	fileOffset	The offset of the log record from the start of the file.
private int	logFileNo	The number of the write-ahead log file that the record is stored in.
private int	recordSize	The size of the record that this LSN points to, in bytes.

Constructor Summary

Constructors

Constructor	Description
LogSequenceNumber(int logFileNo, int fileOffset)
LogSequenceNumber(int logFileNo, int fileOffset, int recordSize)
LogSequenceNumber(LogSequenceNumber lsn, int recordSize)

Method Summary

Modifier and Type	Method	Description
LogSequenceNumber	clone()
int	compareTo(LogSequenceNumber lsn)
boolean	equals(java.lang.Object obj)
int	getFileOffset()	Returns the offset from the start of the WAL file that this record appears at.
int	getLogFileNo()	Returns the file number of the WAL file that this record is in.
int	getRecordSize()
int	hashCode()	Calculate a hash-code for this log-sequence number object.
java.lang.String	toString()

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

logFileNo

private int logFileNo

The number of the write-ahead log file that the record is stored in.

fileOffset

private int fileOffset

The offset of the log record from the start of the file.

recordSize

private int recordSize

The size of the record that this LSN points to, in bytes.

Constructor Detail

LogSequenceNumber

public LogSequenceNumber(int logFileNo,
                         int fileOffset,
                         int recordSize)

LogSequenceNumber

public LogSequenceNumber(int logFileNo,
                         int fileOffset)

LogSequenceNumber

public LogSequenceNumber(LogSequenceNumber lsn,
                         int recordSize)

Method Detail

equals

public boolean equals(java.lang.Object obj)

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

Calculate a hash-code for this log-sequence number object.

Overrides:

hashCode in class java.lang.Object

clone

public LogSequenceNumber clone()

Overrides:

clone in class java.lang.Object

getLogFileNo

public int getLogFileNo()

Returns the file number of the WAL file that this record is in.

Returns:

the file number of the WAL file that this record is in.

getFileOffset

public int getFileOffset()

Returns the offset from the start of the WAL file that this record appears at.

Returns:

the offset from the start of the WAL file that this record appears at.

getRecordSize

public int getRecordSize()

compareTo

public int compareTo(LogSequenceNumber lsn)

Specified by:

compareTo in interface java.lang.Comparable<LogSequenceNumber>

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object