Perf: Lazy compute total byte count of all searchable files

This avoids accessing FileContentsPieces

src/Server/FileSystemDatabase/FileDatabaseSnapshot.cs

@@ -25,6 +25,7 @@ public class FileDatabaseSnapshot : IFileDatabaseSnapshot {
     private readonly Lazy<IList<FileName>> _fileNames;
     private readonly Lazy<IList<FileContentsPiece>> _fileContentsPieces;
     private readonly Lazy<long> _searchableFileCount;
+    private readonly Lazy<long> _totalFileContentsLength;
 
     public FileDatabaseSnapshot(IDictionary<FullPath, string> projectHashes, 
       IDictionary<DirectoryName, DirectoryData> directories,
@@ -35,6 +36,7 @@ public FileDatabaseSnapshot(IDictionary<FullPath, string> projectHashes,
       _fileNames = new Lazy<IList<FileName>>(CreateFileNames);
       _fileContentsPieces = new Lazy<IList<FileContentsPiece>>(CreateFilePieces, LazyThreadSafetyMode.ExecutionAndPublication);
       _searchableFileCount = new Lazy<long>(CountFilesWithContents);
+      _totalFileContentsLength = new Lazy<long>(ComputeTotalFileContentsLength);
     }
 
     public IDictionary<FullPath, string> ProjectHashes => _projectHashes;
@@ -54,6 +56,7 @@ public FileDatabaseSnapshot(IDictionary<FullPath, string> projectHashes,
     public IList<FileName> FileNames => _fileNames.Value;
     public IList<FileContentsPiece> FileContentsPieces => _fileContentsPieces.Value;
     public long SearchableFileCount => _searchableFileCount.Value;
+    public long TotalFileContentsLength => _totalFileContentsLength.Value;
 
     public IEnumerable<FileExtract> GetFileExtracts(FileName filename, IEnumerable<FilePositionSpan> spans,
       int maxLength) {
@@ -113,5 +116,9 @@ private IList<FileContentsPiece> CreateFilePieces() {
     private long CountFilesWithContents() {
       return _files.Values.Where(FileDatabaseBuilder.FileHasContents).Count();
     }
+
+    private long ComputeTotalFileContentsLength() {
+      return _files.Values.Where(x => x.Contents != null).Aggregate(0L, (acc, x) => acc + x.Contents.ByteLength);
+    }
   }
 }

src/Server/FileSystemDatabase/IFileDatabaseSnapshot.cs

@@ -32,6 +32,8 @@ public interface IFileDatabaseSnapshot {
     /// </summary>
     long SearchableFileCount { get; }
 
+    long TotalFileContentsLength { get; }
+
     /// <summary>
     /// Returns the list of text extracts for a given <paramref
     /// name="fileName"/> and list of <paramref name="spans"/>. <paramref

src/Server/Ipc/TypedMessageHandlers/GetDatabaseStatisticsRequestHandler.cs

@@ -40,7 +40,7 @@ public override TypedResponse Process(TypedRequest typedRequest) {
         ProjectCount = snapshot.ProjectRoots.Count,
         FileCount = database.FileNames.Count,
         SearchableFileCount = database.SearchableFileCount,
-        ServerNativeMemoryUsage = database.FileContentsPieces.Aggregate(0L, (x, piece) => x + piece.ByteLength),
+        ServerNativeMemoryUsage = database.TotalFileContentsLength,
         IndexLastUpdatedUtc = indexingServerState.LastIndexUpdateUtc,
         ServerGcMemoryUsage = GC.GetTotalMemory(false),
         ServerStatus = indexingServerState.Status,