/// <summary>
/// Initialize LiteEngine using initial engine settings
/// </summary>
public LiteEngine(EngineSettings settings)
{
_settings = settings ?? throw new ArgumentNullException(nameof(settings));
// clear checkpoint if database is readonly
if (_settings.ReadOnly)
{
_settings.Checkpoint = 0;
}
LOG($"start initializing{(_settings.ReadOnly ? " (readonly)" : "")}", "ENGINE");
try
{
// initialize locker service (no dependency)
_locker = new LockService(settings.Timeout, settings.ReadOnly);
// initialize disk service (will create database if needed)
_disk = new DiskService(settings);
// read page with no cache ref (has a own PageBuffer) - do not Release() support
var buffer = _disk.ReadFull(FileOrigin.Data).First();
// if first byte are 1 this datafile are encrypted but has do defined password to open
if (buffer[0] == 1)
{
throw new LiteException(0, "This data file is encrypted and needs a password to open");
}
_header = new HeaderPage(buffer);
// initialize wal-index service
_walIndex = new WalIndexService(_disk, _locker);
// if exists log file, restore wal index references (can update full _header instance)
if (_disk.GetLength(FileOrigin.Log) > 0)
{
_walIndex.RestoreIndex(ref _header);
}
// initialize sort temp disk
_sortDisk = new SortDisk(settings.CreateTempFactory(), CONTAINER_SORT_SIZE, settings.UtcDate);
// initialize transaction monitor as last service
_monitor = new TransactionMonitor(_header, _locker, _disk, _walIndex, _settings);
// register system collections
this.InitializeSystemCollections();
LOG("initialization completed", "ENGINE");
}
catch (Exception ex)
{
LOG(ex.Message, "ERROR");
// explicit dispose (but do not run shutdown operation)
this.Dispose(true);
throw;
}
}
/// <summary>
/// Do checkpoint operation to copy log pages into data file. Return how many transactions was commited inside data file
/// Checkpoint requires exclusive lock database
/// </summary>
public int Checkpoint()
{
// no log file or no confirmed transaction, just exit
if (_disk.GetLength(FileOrigin.Log) == 0 || _confirmTransactions.Count == 0)
{
return(0);
}
var mustExit = _locker.EnterExclusive();
try
{
return(this.CheckpointInternal());
}
finally
{
if (mustExit)
{
_locker.ExitExclusive();
}
}
}
/// <summary>
/// Do checkpoint operation to copy log pages into data file. Return how many transactions was commited inside data file
/// If soft = true, just try enter in exclusive mode - if not possible, just exit
/// </summary>
public void Checkpoint(bool soft)
{
// get original log length
var logLength = _disk.GetLength(FileOrigin.Log);
// no log file or no confirmed transaction, just exit
if (logLength == 0 || _confirmTransactions.Count == 0)
{
return;
}
// for safe, lock all database (read/write) before run checkpoint operation
// future versions can be smarter and avoid lock (be more like SQLite checkpoint)
if (soft)
{
// shutdown mode only try enter in exclusive mode... if not possible, exit without checkpoint
if (_locker.TryEnterExclusive() == false)
{
return;
}
}
else
{
_locker.EnterReserved(true);
}
LOG($"checkpoint", "WAL");
// wait all pages write on disk
_disk.Queue.Wait();
ENSURE(_disk.Queue.Length == 0, "no pages on queue when checkpoint");
// getting all "good" pages from log file to be copied into data file
IEnumerable <PageBuffer> source()
{
foreach (var buffer in _disk.ReadFull(FileOrigin.Log))
{
// read direct from buffer to avoid create BasePage structure
var transactionID = buffer.ReadUInt32(BasePage.P_TRANSACTION_ID);
// only confied paged can be write on data disk
if (_confirmTransactions.Contains(transactionID))
{
var pageID = buffer.ReadUInt32(BasePage.P_PAGE_ID);
// clear isConfirmed/transactionID
buffer.Write(uint.MaxValue, BasePage.P_TRANSACTION_ID);
buffer.Write(false, BasePage.P_IS_CONFIRMED);
buffer.Position = BasePage.GetPagePosition(pageID);
yield return(buffer);
}
}
}
// write all log pages into data file (sync)
_disk.Write(source(), FileOrigin.Data);
// reset
_confirmTransactions.Clear();
_index.Clear();
_currentReadVersion = 0;
// clear cache
_disk.Cache.Clear();
// clear log file (sync)
_disk.SetLength(0, FileOrigin.Log);
// remove exclusive lock
_locker.ExitReserved(true);
}
