Package edu.caltech.nanodb.transactions

Class TransactionStatePage

java.lang.Object

edu.caltech.nanodb.transactions.TransactionStatePage

public class TransactionStatePage
extends java.lang.Object

This class wraps the transaction-state page to provide basic operations necessary for reading and storing essential values. The values stored in the transaction-state file are as follows:

• Next Transaction ID. This is the next transaction ID, as recorded by the database at the last point this file was saved.
• First Log Sequence Number (LSN). This is the LSN in the write-ahead log (WAL) where recovery should start from. It denotes a point in time where all table files and the WAL are completely in sync with each other. Since NanoDB doesn't support checkpointing (yet), this value is usually updated after recovery is completed, and also upon proper shutdown of the database.
• Next LSN. This value is one byte past the last valid WAL record that has been successfully written and sync'd to the write-ahead log. Note that this value may be behind the WALManager.nextLSN value stored in memory.

Field Summary

Fields

Modifier and Type	Field	Description
private DBPage	dbPage
static int	OFFSET_FIRST_LSN_FILENUM	The offset in the checkpoint page where the "First Log Sequence Number" file-number is stored.
static int	OFFSET_FIRST_LSN_OFFSET	The offset in the checkpoint page where the "First Log Sequence Number" file-offset is stored.
static int	OFFSET_NEXT_LSN_FILENUM	The offset in the checkpoint page where the "Next Log Sequence Number" file-number is stored.
static int	OFFSET_NEXT_LSN_OFFSET	The offset in the checkpoint page where the "Next Log Sequence Number" file-offset is stored.
static int	OFFSET_NEXT_TXN_ID	The offset in the checkpoint page where the "Next Transaction ID" value is stored.

Constructor Summary

Constructors

Constructor	Description
TransactionStatePage(DBPage dbPage)

Method Summary

Modifier and Type	Method	Description
LogSequenceNumber	getFirstLSN()
LogSequenceNumber	getNextLSN()
int	getNextTransactionID()
void	setFirstLSN(LogSequenceNumber firstLSN)
void	setNextLSN(LogSequenceNumber nextLSN)
void	setNextTransactionID(int nextTransactionID)

Methods inherited from class java.lang.Object

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

Field Detail

OFFSET_NEXT_TXN_ID

public static final int OFFSET_NEXT_TXN_ID

The offset in the checkpoint page where the "Next Transaction ID" value is stored. This value is a signed int (4 bytes).

See Also:

Constant Field Values

OFFSET_FIRST_LSN_FILENUM

public static final int OFFSET_FIRST_LSN_FILENUM

The offset in the checkpoint page where the "First Log Sequence Number" file-number is stored. This value is an unsigned short (2 bytes).

See Also:

Constant Field Values

OFFSET_FIRST_LSN_OFFSET

public static final int OFFSET_FIRST_LSN_OFFSET

The offset in the checkpoint page where the "First Log Sequence Number" file-offset is stored. This value is a signed int (4 bytes).

See Also:

Constant Field Values

OFFSET_NEXT_LSN_FILENUM

public static final int OFFSET_NEXT_LSN_FILENUM

The offset in the checkpoint page where the "Next Log Sequence Number" file-number is stored. This value is an unsigned short (2 bytes).

See Also:

Constant Field Values

OFFSET_NEXT_LSN_OFFSET

public static final int OFFSET_NEXT_LSN_OFFSET

The offset in the checkpoint page where the "Next Log Sequence Number" file-offset is stored. This value is a signed int (4 bytes).

See Also:

Constant Field Values

dbPage

private DBPage dbPage

Constructor Detail

TransactionStatePage

public TransactionStatePage(DBPage dbPage)

Method Detail

getNextTransactionID

public int getNextTransactionID()

setNextTransactionID

public void setNextTransactionID(int nextTransactionID)

getFirstLSN

public LogSequenceNumber getFirstLSN()

setFirstLSN

public void setFirstLSN(LogSequenceNumber firstLSN)

getNextLSN

public LogSequenceNumber getNextLSN()

setNextLSN

public void setNextLSN(LogSequenceNumber nextLSN)