simpledb

Class LockManager

java.lang.Object

simpledb.LockManager

public class LockManager
extends java.lang.Object

LockManager is class which manages locks for transactions. It stores states of various locks on pages and provides atomic grant and release of locks.

Author:

hrishi

Field Summary

Fields

Modifier and Type	Field and Description
private java.util.HashMap<TransactionId,java.util.Set<PageId>>	exclusivePages
private java.util.HashMap<PageId,java.util.Set<TransactionId>>	readLocks
private java.util.HashMap<TransactionId,java.util.Set<PageId>>	sharedPages
private java.util.HashMap<PageId,TransactionId>	writeLock

Constructor Summary

Constructors

Constructor and Description
LockManager()

Method Summary

Modifier and Type	Method and Description
private void	addLock(TransactionId tid, PageId pid, Permissions pm)
boolean	grantLock(TransactionId tid, PageId pid, Permissions pm) Grants lock to the Transaction.
boolean	holdsLock(TransactionId tid, PageId pid) Checks if transaction has lock on a page
void	releaseAllPages(TransactionId tid) Releases all pages associated with given Transaction.
void	releaseLock(TransactionId tid, PageId pid) Releases locks associated with given transaction and page.
void	removePage(PageId pid) Releases Lock related to a page

Methods inherited from class java.lang.Object

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

Field Detail

readLocks

private java.util.HashMap<PageId,java.util.Set<TransactionId>> readLocks

writeLock

private java.util.HashMap<PageId,TransactionId> writeLock

sharedPages

private java.util.HashMap<TransactionId,java.util.Set<PageId>> sharedPages

exclusivePages

private java.util.HashMap<TransactionId,java.util.Set<PageId>> exclusivePages

Constructor Detail

LockManager

public LockManager()

Method Detail

holdsLock

public boolean holdsLock(TransactionId tid,
                         PageId pid)

Checks if transaction has lock on a page

Parameters:

tid - Transaction Id

pid - Page Id

Returns:

boolean True if holds lock

addLock

private void addLock(TransactionId tid,
                     PageId pid,
                     Permissions pm)

grantLock

public boolean grantLock(TransactionId tid,
                         PageId pid,
                         Permissions pm)

Grants lock to the Transaction.

Parameters:

tid - TransactionId requesting lock.

pid - PageId on which the lock is requested.

pm - The type of permission.

Returns:

boolean True if lock is successfully granted.

releaseLock

public void releaseLock(TransactionId tid,
                        PageId pid)

Releases locks associated with given transaction and page.

Parameters:

tid - The TransactionId.

pid - The PageId.

removePage

public void removePage(PageId pid)

Releases Lock related to a page

Parameters:

pid - PageId

releaseAllPages

public void releaseAllPages(TransactionId tid)

Releases all pages associated with given Transaction.

Parameters:

tid - The TransactionId.