/// <summary>
/// Load all confirmed transactions from log file (used only when open datafile)
/// Don't need lock because it's called on ctor of LiteEngine
/// </summary>
public void RestoreIndex(ref HeaderPage header)
{
// get all page positions
var positions = new Dictionary <long, List <PagePosition> >();
var current = 0L;
// read all pages to get confirmed transactions (do not read page content, only page header)
foreach (var buffer in _disk.ReadFull(FileOrigin.Log))
{
// read direct from buffer to avoid create BasePage structure
var pageID = buffer.ReadUInt32(BasePage.P_PAGE_ID);
var isConfirmed = buffer.ReadBool(BasePage.P_IS_CONFIRMED);
var transactionID = buffer.ReadUInt32(BasePage.P_TRANSACTION_ID);
var position = new PagePosition(pageID, current);
if (positions.TryGetValue(transactionID, out var list))
{
list.Add(position);
}
else
{
positions[transactionID] = new List <PagePosition> {
position
};
}
if (isConfirmed)
{
this.ConfirmTransaction(transactionID, positions[transactionID]);
var pageType = (PageType)buffer.ReadByte(BasePage.P_PAGE_TYPE);
// when a header is modified in transaction, must always be the last page inside log file (per transaction)
if (pageType == PageType.Header)
{
// page buffer instance can't change
var headerBuffer = header.Buffer;
// copy this buffer block into original header block
Buffer.BlockCopy(buffer.Array, buffer.Offset, headerBuffer.Array, headerBuffer.Offset, PAGE_SIZE);
// re-load header (using new buffer data)
header = new HeaderPage(headerBuffer);
header.TransactionID = uint.MaxValue;
header.IsConfirmed = false;
}
}
// update last transaction ID
_lastTransactionID = (int)transactionID;
current += PAGE_SIZE;
}
}
/// <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);
}
}
/// <summary>
/// Load all confirmed transactions from log file (used only when open datafile)
/// Don't need lock because it's called on ctor of LiteEngine
/// Update _disk instance with last log position
/// </summary>
public void RestoreIndex(HeaderPage header)
{
// get all page positions
var positions = new Dictionary <long, List <PagePosition> >();
var last = 0L;
// read all pages to get confirmed transactions (do not read page content, only page header)
foreach (var buffer in _disk.ReadLog(true))
{
// read direct from buffer to avoid create BasePage structure
var pageID = buffer.ReadUInt32(BasePage.P_PAGE_ID);
var isConfirmed = buffer.ReadBool(BasePage.P_IS_CONFIRMED);
var transactionID = buffer.ReadUInt32(BasePage.P_TRANSACTION_ID);
if (transactionID == 0 || transactionID == uint.MaxValue)
{
continue;
}
var position = new PagePosition(pageID, buffer.Position);
if (positions.TryGetValue(transactionID, out var list))
{
list.Add(position);
}
else
{
positions[transactionID] = new List <PagePosition> {
position
};
}
if (isConfirmed)
{
// update last IsConfirmed page
last = buffer.Position;
this.ConfirmTransaction(transactionID, positions[transactionID]);
var pageType = (PageType)buffer.ReadByte(BasePage.P_PAGE_TYPE);
// when a header is modified in transaction, must always be the last page inside log file (per transaction)
if (pageType == PageType.Header)
{
// copy this buffer block into original header block
Buffer.BlockCopy(buffer.Array, buffer.Offset, header.Buffer.Array, header.Buffer.Offset, PAGE_SIZE);
header.LoadPage();
}
}
// update last transaction ID
_lastTransactionID = (int)transactionID;
}
// update last log position acording with last IsConfirmed on log
if (last > 0)
{
_disk.LogEndPosition = last + PAGE_SIZE;
}
}
