/// <summary>
/// Shrinks database transactions and reduces file size on disk
/// </summary>
/// <returns></returns>
public async Task <ShrinkInfo> Shrink()
{
ShrinkInfo info = null;
try
{
Stream stream = File.GetStream();
List <string> msgs;
long position;
int count;
await WaitForLock();
try
{
count = _deletedMessages.Count;
position = stream.Position;
msgs = _deletedMessages.Count > 0
? new List <string>(_deletedMessages)
: new List <string>();
}
finally
{
ReleaseLock();
}
info = await _shrinkManager.Shrink(position, msgs);
//sync deleted messages array
if (info.Successful)
{
if (count > 0)
{
await WaitForLock();
try
{
if (_deletedMessages.Count > count)
{
_deletedMessages = _deletedMessages.GetRange(count, _deletedMessages.Count - count);
}
else
{
_deletedMessages.Clear();
}
}
finally
{
ReleaseLock();
}
}
}
OnShrink?.Invoke(this, info);
}
catch (Exception ex)
{
if (info == null)
{
info = new ShrinkInfo();
}
info.Error = ex;
TriggerError(ErrorHint.Shrink, ex);
}
return(info);
}
/// <summary>
/// Shrinks database file from begin to position pointer.
/// This is a partial shrink and can run almost without any lock and thread-block operations.
/// </summary>
public async Task <ShrinkInfo> Shrink(long position, List <string> deletedMessages)
{
_info = new ShrinkInfo();
if (_shrinking)
{
return(_info);
}
Stopwatch sw = new Stopwatch();
sw.Start();
try
{
_shrinking = true;
_end = position;
_deletingMessages = new HashSet <string>(deletedMessages);
_info.OldSize = _end;
if (_source != null)
{
await DisposeSource();
}
await using (FileStream file = new FileStream(_database.File.Filename, FileMode.Open, FileAccess.Read, FileShare.ReadWrite))
{
int capacity = Convert.ToInt32(_end);
_source = new MemoryStream(capacity);
await CopyStream(file, _source, capacity);
_source.Position = 0;
}
_target = new FileStream(_database.File.Filename + ".shrink", FileMode.Create, FileAccess.Write, FileShare.ReadWrite);
sw.Stop();
_info.PreparationDuration = sw.Elapsed;
sw.Reset();
sw.Start();
bool proceed = await ProcessShrink();
sw.Stop();
_info.TruncateDuration = sw.Elapsed;
sw.Reset();
if (!proceed)
{
_shrinking = false;
return(_info);
}
sw.Start();
bool sync = await SyncShrink();
sw.Stop();
_info.SyncDuration = sw.Elapsed;
_info.Successful = sync;
return(_info);
}
finally
{
ShrinkRequired = false;
_shrinking = false;
}
}
