public TransactionService(HeaderPage header, DiskService disk, WalIndexService walIndex)
{
// retain instances
_header = header;
_disk = disk;
_walIndex = walIndex;
// create new transactionID
_transactionID = walIndex.NextTransactionID();
_startTime = DateTime.UtcNow;
}
public TransactionService(HeaderPage header, LockService locker, DiskService disk, WalIndexService walIndex, int maxTransactionSize, TransactionMonitor monitor, bool queryOnly)
{
// retain instances
_header = header;
_locker = locker;
_disk = disk;
_walIndex = walIndex;
_monitor = monitor;
this.QueryOnly = queryOnly;
this.MaxTransactionSize = maxTransactionSize;
// create new transactionID
_transactionID = walIndex.NextTransactionID();
_startTime = DateTime.UtcNow;
_reader = _disk.GetReader();
}
public TransactionService(HeaderPage header, LockService locker, DiskService disk, WalIndexService walIndex, int maxTransactionSize, Action <uint> done)
{
// retain instances
_header = header;
_locker = locker;
_disk = disk;
_walIndex = walIndex;
_maxTransactionSize = maxTransactionSize;
_done = done;
// create new transactionID
_transactionID = walIndex.NextTransactionID();
_startTime = DateTime.UtcNow;
_reader = _disk.GetReader();
// enter transaction locker to avoid 2 transactions in same thread
_locker.EnterTransaction();
}
/// <summary>
/// Return added pages when occurs an rollback transaction (run this only in rollback). Create new transactionID and add into
/// Log file all new pages as EmptyPage in a linked order - also, update SharedPage before store
/// </summary>
private void ReturnNewPages()
{
// create new transaction ID
var transactionID = _walIndex.NextTransactionID();
// now lock header to update LastTransactionID/FreePageList
lock (_header)
{
// persist all empty pages into wal-file
var pagePositions = new Dictionary <uint, PagePosition>();
IEnumerable <PageBuffer> source()
{
// create list of empty pages with forward link pointer
for (var i = 0; i < _transPages.NewPages.Count; i++)
{
var pageID = _transPages.NewPages[i];
var next = i < _transPages.NewPages.Count - 1 ? _transPages.NewPages[i + 1] : _header.FreeEmptyPageID;
var buffer = _disk.NewPage();
var page = new BasePage(buffer, pageID, PageType.Empty)
{
NextPageID = next,
TransactionID = transactionID
};
yield return(page.UpdateBuffer());
// update wal
pagePositions[pageID] = new PagePosition(pageID, buffer.Position);
if (_disposed)
{
yield break;
}
}
// update header page with my new transaction ID
_header.TransactionID = transactionID;
_header.FreeEmptyPageID = _transPages.NewPages[0];
_header.IsConfirmed = true;
// clone header buffer
var buf = _header.UpdateBuffer();
var clone = _disk.NewPage();
Buffer.BlockCopy(buf.Array, buf.Offset, clone.Array, clone.Offset, clone.Count);
yield return(clone);
};
// create a header save point before any change
var safepoint = _header.Savepoint();
try
{
// write all pages (including new header)
_disk.WriteAsync(source());
}
catch
{
// must revert all header content if any error occurs during header change
_header.Restore(safepoint);
throw;
}
// now confirm this transaction to wal
_walIndex.ConfirmTransaction(transactionID, pagePositions.Values);
}
}
