simpledb.tx.recovery
Class CheckpointRecord

java.lang.Object
  simpledb.tx.recovery.CheckpointRecord

All Implemented Interfaces:

LogRecord

 class CheckpointRecord
extends java.lang.Object
implements LogRecord

The CHECKPOINT log record.

Author:

Edward Sciore

Field Summary

Fields inherited from interface simpledb.tx.recovery.LogRecord

CHECKPOINT, COMMIT, logMgr, ROLLBACK, SETINT, SETSTRING, START

Constructor Summary

CheckpointRecord()
Creates a quiescent checkpoint record.

CheckpointRecord(BasicLogRecord rec)
Creates a log record by reading no other values from the basic log record.

Method Summary

int	op() Returns the log record's type.
java.lang.String	toString()
int	txNumber() Checkpoint records have no associated transaction, and so the method returns a "dummy", negative txid.
void	undo(int txnum) Does nothing, because a checkpoint record contains no undo information.
int	writeToLog() Writes a checkpoint record to the log.

Methods inherited from class java.lang.Object

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

Constructor Detail

CheckpointRecord

public CheckpointRecord()

Creates a quiescent checkpoint record.

CheckpointRecord

public CheckpointRecord(BasicLogRecord rec)

Creates a log record by reading no other values from the basic log record.

Parameters:

rec - the basic log record

Method Detail

writeToLog

public int writeToLog()

Writes a checkpoint record to the log. This log record contains the CHECKPOINT operator, and nothing else.

Specified by:

writeToLog in interface LogRecord

Returns:

the LSN of the last log value

op

public int op()

Description copied from interface: LogRecord

Returns the log record's type.

Specified by:

op in interface LogRecord

Returns:

the log record's type

txNumber

public int txNumber()

Checkpoint records have no associated transaction, and so the method returns a "dummy", negative txid.

Specified by:

txNumber in interface LogRecord

Returns:

the log record's transaction id

undo

public void undo(int txnum)

Does nothing, because a checkpoint record contains no undo information.

Specified by:

undo in interface LogRecord

Parameters:

txnum - the id of the transaction that is performing the undo.

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object