private void WriteDBRoot(DBHdr dbRoot)
{
StoragePage rootPage = new StoragePage();
rootPage.AddRecord(dbRoot);
rootPage.WritePageData(this.dataFile, RootPage);
}
/// <summary>
/// Remarks:
/// No locking needed beause this method cannot be invoked on the object.
/// It is only called during initialization before the object is returned
/// from the object factory method.
/// </summary>
/// <param name="filePath"></param>
private void Init(string filePath)
{
// open the file
this.dataFile = FileStreamWrapper.CreateObject(filePath);
DBHdr dbRoot = this.ReadDBRoot();
if (null == dbRoot)
{
// setup the data file
this.InitializeDataFile();
// flush the file
this.dataFile.Flush(true);
}
else
{
// read the prepared transaction data
this.preparedContextMap.ReadTransactionTableData(
this.dataFile, dbRoot.PrepedTransactions);
// read the data manager
this.pageManager.ReadPageManagerData(
this.dataFile, dbRoot.PageManager);
}
}
// implements the abort of a transaction
private void aAbort(Transaction context)
{
lock (ManagerLock)
{
List <int> oldStorageContextPages = new List <int>();
StorageContext storageContext = null;
if (this.activeContextMap.TryGetValue(context, out storageContext))
{
// found transaction in active transactions list
this.activeContextMap.Remove(context);
}
else
{
TransItem contextData = this.preparedContextMap.Remove(context);
if (null == contextData)
{
// transaction must already have been commited or aborted
// nothing to do
return;
}
// found transaction in prepared transaction list
oldStorageContextPages = contextData.StoragePageList;
storageContext = contextData.TransactionData;
if (null == storageContext)
{
storageContext = ReadStorageContext(contextData, out oldStorageContextPages);
}
}
DBHdr dbRoot = this.ReadDBRoot();
if (null == dbRoot)
{
throw new Exception();
}
// write the updated prepared transaction list
List <int> oldPrepedContextMapPages = null;
dbRoot.PrepedTransactions = this.preparedContextMap.WriteTransactionTableData(
this.dataFile, this.pageManager, out oldPrepedContextMapPages);
// update the page manager
this.pageManager.SetFreePages(oldStorageContextPages);
this.pageManager.SetFreePages(oldPrepedContextMapPages);
this.pageManager.SetFreePages(storageContext.AllocatedPageList);
dbRoot.PageManager = this.pageManager.WritePageManagerData(
this.dataFile);
this.WriteDBRoot(dbRoot);
this.dataFile.Flush(true);
}
}
// prepares a transaction for commit by serialializing the data to disk
private void aPrepare(Transaction context)
{
lock (ManagerLock)
{
if (this.preparedContextMap.Contains(context))
{
// transaction already prepared for commit
// nothing to do
return;
}
StorageContext storageContext = null;
if (!this.activeContextMap.TryGetValue(context, out storageContext))
{
// oops ... we don't know anything about this transaction
// something must have gone wrong
throw new Exception();
}
this.activeContextMap.Remove(context);
// add the new item to the table
TransItem contextData = WriteStorageContext(storageContext);
contextData.Transaction = context;
contextData.TransactionData = storageContext;
this.preparedContextMap.Add(contextData);
// update the DB root for the free list page and
// commited transaction list
DBHdr dbRoot = this.ReadDBRoot();
if (null == dbRoot)
{
throw new InvalidDataException();
}
// write the prepared transactions table
List <int> oldContextMapPages = null;
dbRoot.PrepedTransactions = this.preparedContextMap.WriteTransactionTableData(
this.dataFile, this.pageManager, out oldContextMapPages);
// write the page manager
this.pageManager.SetFreePages(oldContextMapPages);
dbRoot.PageManager = this.pageManager.WritePageManagerData(
this.dataFile);
this.WriteDBRoot(dbRoot);
this.dataFile.Flush(true);
}
}
private DBHdr ReadDBRoot()
{
DBHdr dbRoot = null;
try
{
StoragePage rootPage = new StoragePage();
rootPage.ReadPageData(this.dataFile, RootPage);
dbRoot = (DBHdr)rootPage.ReadRecord(0);
}
catch (Exception)
{
dbRoot = null;
}
return(dbRoot);
}
private StorageContext aGetStorageContext(Transaction context)
{
lock (dataFile)
{
// look for the context in the map
StorageContext storageContext = null;
if (this.activeContextMap.TryGetValue(context, out storageContext))
{
return(storageContext);
}
// create a brand new storage context
// read the DBRoot record
DBHdr dbRoot = ReadDBRoot();
if (null == dbRoot)
{
throw new Exception();
}
// create the storage context
storageContext = new StorageContext();
// read in the page table
storageContext.PageTable.ReadPageTableData(
this.dataFile, dbRoot.PageTable);
// read in the resource index
storageContext.ResourceIndex.ReadIndexData(
this.dataFile, dbRoot.ResourceIndex);
// read in the reservation index
storageContext.ReservationIndex.ReadIndexData(
this.dataFile, dbRoot.ReservationIndex);
// insert the context into the map
this.activeContextMap.Add(context, storageContext);
return(storageContext);
}
}
private void InitializeDataFile()
{
// helpers
List <int> oldPages = null;
DBHdr dbRoot = new DBHdr();
WriteDBRoot(dbRoot);
// create the page table
StoragePageTable pageTable = new StoragePageTable();
dbRoot.PageTable = pageTable.WritePageTableData(
this.dataFile, this.pageManager, out oldPages);
// create resource index
StorageIndex <RID> resourceIndx = new StorageIndex <RID>();
dbRoot.ResourceIndex = resourceIndx.WriteIndexData(
this.dataFile, this.pageManager, out oldPages);
// create reservation index
StorageIndex <Customer> reservationIndex = new StorageIndex <Customer>();
dbRoot.ReservationIndex = reservationIndex.WriteIndexData(
this.dataFile, this.pageManager, out oldPages);
// create preped transactions index
StorageTransactionTable preparedTransactions = new StorageTransactionTable();
dbRoot.PrepedTransactions = preparedTransactions.WriteTransactionTableData(
this.dataFile, this.pageManager, out oldPages);
// write the page manager
dbRoot.PageManager = this.pageManager.WritePageManagerData(this.dataFile);
// write the dbRoot one more time
WriteDBRoot(dbRoot);
}
// commits a transaction
private void aCommit(Transaction context)
{
lock (ManagerLock)
{
TransItem contextData = this.preparedContextMap.Remove(context);
if (null == contextData)
{
// transaction must already have been commited or aborted
// nothing to do
return;
}
List <int> oldStorageContextPages = contextData.StoragePageList;
StorageContext storageContext = contextData.TransactionData;
if (null == storageContext)
{
storageContext = ReadStorageContext(contextData, out oldStorageContextPages);
}
// read in the DB root
DBHdr dbRoot = this.ReadDBRoot();
if (null == dbRoot)
{
throw new InvalidDataException();
}
// merge page table
storageContext.PageTable.ReadPageTableData(
this.dataFile, dbRoot.PageTable);
storageContext.PageTable.ClearDirtyFlags();
// merge resource index
storageContext.ResourceIndex.ReadIndexData(
this.dataFile, dbRoot.ResourceIndex);
storageContext.ResourceIndex.ClearDirtyFlags();
// merge reservation index
storageContext.ReservationIndex.ReadIndexData(
this.dataFile, dbRoot.ReservationIndex);
storageContext.ReservationIndex.ClearDirtyFlags();
// write the page table
List <int> oldPageTablePages = null;
dbRoot.PageTable = storageContext.PageTable.WritePageTableData(
this.dataFile, this.pageManager, out oldPageTablePages);
// write the resource index
List <int> oldResourceIndexPages = null;
dbRoot.ResourceIndex = storageContext.ResourceIndex.WriteIndexData(
this.dataFile, this.pageManager, out oldResourceIndexPages);
// write the reservation index
List <int> oldReservationIndexPages = null;
dbRoot.ReservationIndex = storageContext.ReservationIndex.WriteIndexData(
this.dataFile, this.pageManager, out oldReservationIndexPages);
// write the updated prepared transaction list
List <int> oldPrepedContextMapPages = null;
dbRoot.PrepedTransactions = this.preparedContextMap.WriteTransactionTableData(
this.dataFile, this.pageManager, out oldPrepedContextMapPages);
// update the page manager
this.pageManager.SetFreePages(oldStorageContextPages);
this.pageManager.SetFreePages(oldPageTablePages);
this.pageManager.SetFreePages(oldResourceIndexPages);
this.pageManager.SetFreePages(oldReservationIndexPages);
this.pageManager.SetFreePages(oldPrepedContextMapPages);
this.pageManager.SetFreePages(storageContext.FreedPageList);
dbRoot.PageManager = this.pageManager.WritePageManagerData(
this.dataFile);
this.WriteDBRoot(dbRoot);
this.dataFile.Flush(true);
}
}
