private ScratchBufferItem NextFile(long minSize, long?requestedSize)
{
var current = _recycleArea.Last;
var oldestTx = _env.PossibleOldestReadTransaction(null);
while (current != null)
{
var recycled = current.Value;
if (recycled.File.Size >= Math.Max(minSize, requestedSize ?? 0) &&
// even though this is in the recyle bin, there might still be some transactions looking at it
// so we have to make sure that this is really unused before actually reusing it
recycled.File.HasActivelyUsedBytes(oldestTx) == false)
{
recycled.File.Reset();
recycled.RecycledAt = default(DateTime);
_recycleArea.Remove(current);
AddScratchBufferFile(recycled);
_scratchSpaceMonitor.Increase(recycled.File.NumberOfAllocatedPages * Constants.Storage.PageSize);
return(recycled);
}
current = current.Previous;
}
_currentScratchNumber++;
AbstractPager scratchPager;
if (requestedSize != null)
{
try
{
scratchPager =
_options.CreateScratchPager(StorageEnvironmentOptions.ScratchBufferName(_currentScratchNumber),
requestedSize.Value);
}
catch (Exception)
{
// this can fail because of disk space issue, let us just ignore it
// we'll allocate the minimum amount in a bit anyway
return(NextFile(minSize, null));
}
}
else
{
scratchPager = _options.CreateScratchPager(StorageEnvironmentOptions.ScratchBufferName(_currentScratchNumber),
Math.Max(_options.InitialLogFileSize, minSize));
}
var scratchFile = new ScratchBufferFile(scratchPager, _currentScratchNumber);
var item = new ScratchBufferItem(scratchFile.Number, scratchFile);
AddScratchBufferFile(item);
_scratchSpaceMonitor.Increase(item.File.NumberOfAllocatedPages * Constants.Storage.PageSize);
return(item);
}