Fixed: Performance issue when scanning large root folder

src/NzbDrone.Common/Disk/DiskProviderBase.cs

@@ -141,6 +141,13 @@ namespace NzbDrone.Common.Disk
             }
         }
 
+        public bool FolderEmpty(string path)
+        {
+            Ensure.That(path, () => path).IsValidPath();
+
+            return Directory.EnumerateDirectories(path).Empty();
+        }
+
         public string[] GetDirectories(string path)
         {
             Ensure.That(path, () => path).IsValidPath();

src/NzbDrone.Common/Disk/IDiskProvider.cs

@@ -21,6 +21,7 @@ namespace NzbDrone.Common.Disk
         bool FileExists(string path);
         bool FileExists(string path, StringComparison stringComparison);
         bool FolderWritable(string path);
+        bool FolderEmpty(string path);
         string[] GetDirectories(string path);
         string[] GetFiles(string path, SearchOption searchOption);
         long GetFolderSize(string path);

src/NzbDrone.Core.Test/MediaFiles/DiskScanServiceTests/ScanFixture.cs

@@ -5,6 +5,7 @@ using FizzWare.NBuilder;
 using Moq;
 using NUnit.Framework;
 using NzbDrone.Common.Disk;
+using NzbDrone.Common.Extensions;
 using NzbDrone.Core.Configuration;
 using NzbDrone.Core.MediaFiles;
 using NzbDrone.Core.MediaFiles.EpisodeImport;
@@ -56,6 +57,10 @@ namespace NzbDrone.Core.Test.MediaFiles.DiskScanServiceTests
                   .Setup(s => s.GetDirectories(_rootFolder))
                   .Returns(subfolders);
 
+            Mocker.GetMock<IDiskProvider>()
+                  .Setup(s => s.FolderEmpty(_rootFolder))
+                  .Returns(subfolders.Empty());
+
             foreach (var folder in subfolders)
             {
                 Mocker.GetMock<IDiskProvider>()
@@ -84,7 +89,10 @@ namespace NzbDrone.Core.Test.MediaFiles.DiskScanServiceTests
             ExceptionVerification.ExpectedWarns(1);
 
             Mocker.GetMock<IDiskProvider>()
-                  .Verify(v => v.FolderExists(_series.Path), Times.Never());
+                  .Verify(v => v.GetFiles(_series.Path, SearchOption.AllDirectories), Times.Never());
+
+            Mocker.GetMock<IDiskProvider>()
+                  .Verify(v => v.CreateFolder(_series.Path), Times.Never());
 
             Mocker.GetMock<IMediaFileTableCleanupService>()
                   .Verify(v => v.Clean(It.IsAny<Series>(), It.IsAny<List<string>>()), Times.Never());
@@ -100,7 +108,10 @@ namespace NzbDrone.Core.Test.MediaFiles.DiskScanServiceTests
             ExceptionVerification.ExpectedWarns(1);
 
             Mocker.GetMock<IDiskProvider>()
-                  .Verify(v => v.FolderExists(_series.Path), Times.Never());
+                  .Verify(v => v.GetFiles(_series.Path, SearchOption.AllDirectories), Times.Never());
+
+            Mocker.GetMock<IDiskProvider>()
+                  .Verify(v => v.CreateFolder(_series.Path), Times.Never());
 
             Mocker.GetMock<IMediaFileTableCleanupService>()
                   .Verify(v => v.Clean(It.IsAny<Series>(), It.IsAny<List<string>>()), Times.Never());

src/NzbDrone.Core/MediaFiles/DiskScanService.cs

@@ -69,23 +69,28 @@ namespace NzbDrone.Core.MediaFiles
         {
             var rootFolder = _rootFolderService.GetBestRootFolderPath(series.Path);
 
-            if (!_diskProvider.FolderExists(rootFolder))
-            {
-                _logger.Warn("Series' root folder ({0}) doesn't exist.", rootFolder);
-                _eventAggregator.PublishEvent(new SeriesScanSkippedEvent(series, SeriesScanSkippedReason.RootFolderDoesNotExist));
-                return;
-            }
+            var seriesFolderExists = _diskProvider.FolderExists(series.Path);
 
-            if (_diskProvider.GetDirectories(rootFolder).Empty())
+            if (!seriesFolderExists)
             {
-                _logger.Warn("Series' root folder ({0}) is empty.", rootFolder);
-                _eventAggregator.PublishEvent(new SeriesScanSkippedEvent(series, SeriesScanSkippedReason.RootFolderIsEmpty));
-                return;
+                if (!_diskProvider.FolderExists(rootFolder))
+                {
+                    _logger.Warn("Series' root folder ({0}) doesn't exist.", rootFolder);
+                    _eventAggregator.PublishEvent(new SeriesScanSkippedEvent(series, SeriesScanSkippedReason.RootFolderDoesNotExist));
+                    return;
+                }
+
+                if (_diskProvider.FolderEmpty(rootFolder))
+                {
+                    _logger.Warn("Series' root folder ({0}) is empty.", rootFolder);
+                    _eventAggregator.PublishEvent(new SeriesScanSkippedEvent(series, SeriesScanSkippedReason.RootFolderIsEmpty));
+                    return;
+                }
             }
 
             _logger.ProgressInfo("Scanning {0}", series.Title);
 
-            if (!_diskProvider.FolderExists(series.Path))
+            if (!seriesFolderExists)
             {
                 if (_configService.CreateEmptySeriesFolders)
                 {