Kept the app responsive while a backup copies the index (#1062)

app/MindWork AI Studio/Components/DataBackupPanel.razor.cs

@@ -188,9 +188,11 @@ public partial class DataBackupPanel : MSGComponentBase
             if (selectionResponse.UserCancelled)
                 return;
 
-            this.selectedArchivePath = selectionResponse.SelectedFilePath;
+            var archivePath = this.selectedArchivePath = selectionResponse.SelectedFilePath;
             this.importResult = null;
-            this.preview = await ChatArchiveImporter.ReadPreviewAsync(this.selectedArchivePath, CancellationToken.None);
+
+            // A large backup lists many thousands of files, and reading a ZIP file is mostly synchronous:
+            this.preview = await Task.Run(() => ChatArchiveImporter.ReadPreviewAsync(archivePath, CancellationToken.None));
         }
         finally
         {

app/MindWork AI Studio/Tools/Databases/AGENTS.md

@@ -24,6 +24,11 @@ When working on these, keep in mind:
 - **Let every probe in `GetDisplayInfo()` catch its own failure.** When the method throws, the page
   replaces the *entire* block with the fallback client, so one unreadable value costs all the others
   as well.
+- **SQLite runs its async methods synchronously.** `Microsoft.Data.Sqlite`, and EF Core on top of it,
+  only looks asynchronous: the calling thread does all the work. A statement which may take long, such
+  as `VACUUM` or a check of the whole database, runs in `Task.Run` inside the client, as
+  `BackupToDirectoryAsync` does. Otherwise a click in the user interface which reaches it freezes the
+  whole window until the statement is done.
 - **Raw SQL against SQLite goes through `context.Database.GetDbConnection()`**, not through
   `SqlQueryRaw<T>`: that one expects a column named `Value` and wraps the statement, so a `PRAGMA`
   never works with it.

app/MindWork AI Studio/Tools/Databases/IndexStore/SqliteIndexStoreClientImplementation.cs

@@ -590,9 +590,14 @@ public sealed partial class SqliteIndexStoreClientImplementation(string name, st
     /// GetDbConnection. The connections of the context share one cache, and a shared cache locks
     /// whole tables: reading the whole database for the copy would hold back every writer until the
     /// copy is done. Without pooling, nothing keeps the copy open afterward, so the backup can
-    /// delete it on every OS.
+    /// delete it on every OS.<br/><br/>
+    ///
+    /// SQLite runs its async methods synchronously, and copying and checking a large index takes a
+    /// while. The copy therefore runs on a thread of its own, so that it never holds up its caller.
     /// </remarks>
-    public override async Task<string> BackupToDirectoryAsync(string targetDirectory, CancellationToken token)
+    public override Task<string> BackupToDirectoryAsync(string targetDirectory, CancellationToken token) => Task.Run(() => this.CopyAndCheckAsync(targetDirectory, token), token);
+
+    private async Task<string> CopyAndCheckAsync(string targetDirectory, CancellationToken token)
     {
         Directory.CreateDirectory(targetDirectory);
         var targetPath = Path.Join(targetDirectory, DATABASE_FILENAME);

app/MindWork AI Studio/Tools/Services/DataBackupService.cs

@@ -110,32 +110,16 @@ public sealed class DataBackupService(ILogger<DataBackupService> logger, Setting
         }
 
         this.ReportProgress(new(DataBackupPhase.PREPARING, 0, 0));
-        var indexCopiesDirectory = string.Empty;
         var token = cancellation.Token;
         try
         {
-            var dataDirectory = SettingsManager.DataDirectory ?? throw new InvalidOperationException("The data directory is not known yet.");
-            var configDirectory = SettingsManager.ConfigDirectory ?? throw new InvalidOperationException("The configuration directory is not known yet.");
-            var settings = DataBackupSettings.CopyWithoutPluginObjects(settingsManager.ConfigurationData);
-            var settingsJson = JsonSerializer.Serialize(settings, SettingsManager.JSON_OPTIONS);
-            var organizationPluginFolders = DataBackupContents.FindOrganizationPluginsAmongUserPlugins(PluginFactory.AvailablePlugins.OfType<IAvailablePlugin>(), dataDirectory);
-
-            indexCopiesDirectory = await this.CopyIndexesAsync(token);
-
-            var sources = new DataBackupSources(dataDirectory, configDirectory, settingsJson, indexCopiesDirectory, organizationPluginFolders);
-            var manifest = new DataBackupManifest(
-                DataBackupFormat.FORMAT_VERSION,
-                Assembly.GetExecutingAssembly().GetCustomAttribute<MetaDataAttribute>()?.Version ?? "unknown",
-                settings.Version.ToString(),
-                DateTimeOffset.UtcNow,
-                dataDirectory,
-                configDirectory,
-                !string.IsNullOrWhiteSpace(indexCopiesDirectory),
-                []);
-
+            //
+            // Copying the settings and the index of the data sources takes a while, and SQLite does
+            // its work synchronously, even behind its async methods. The click which starts a backup,
+            // though, arrives on the thread of the user interface, which would stand still meanwhile:
+            //
             var progress = new Progress<DataBackupProgress>(this.ReportProgress);
-            await using (var archiveStream = new FileStream(archivePath, FileMode.Create, FileAccess.Write, FileShare.None, BUFFER_SIZE, FileOptions.Asynchronous | FileOptions.SequentialScan))
-                manifest = await Task.Run(() => DataBackupWriter.WriteAsync(archiveStream, sources, manifest, progress, token), token);
+            var manifest = await Task.Run(() => this.WriteBackupAsync(archivePath, progress, token), token);
 
             logger.LogInformation("Backed up {FileCount} files with {Megabytes:F1} MB into '{ArchivePath}'. The indexes of the data sources are included: {IncludesIndexes}.", manifest.Entries.Count, manifest.Entries.Sum(entry => entry.Size) / (1024d * 1024d), archivePath, manifest.IncludesDataSourceIndexes);
             return this.End(new(true, false, archivePath, manifest.Entries.Count, manifest.Entries.Sum(entry => entry.Size), manifest.IncludesDataSourceIndexes, string.Empty));
@@ -160,7 +144,6 @@ public sealed class DataBackupService(ILogger<DataBackupService> logger, Setting
         }
         finally
         {
-            this.TryDeleteIndexCopies(indexCopiesDirectory);
             lock (this.stateLock)
                 this.running = null;
 
@@ -169,6 +152,46 @@ public sealed class DataBackupService(ILogger<DataBackupService> logger, Setting
         }
     }
 
+    /// <summary>
+    /// Copies the settings and the indexes, and writes them into the backup together with the rest of the data.
+    /// </summary>
+    /// <param name="archivePath">The file of the backup.</param>
+    /// <param name="progress">Receives how far writing got.</param>
+    /// <param name="token">Cancels the backup.</param>
+    /// <returns>The manifest of the backup, as written into it.</returns>
+    private async Task<DataBackupManifest> WriteBackupAsync(string archivePath, IProgress<DataBackupProgress> progress, CancellationToken token)
+    {
+        var indexCopiesDirectory = string.Empty;
+        try
+        {
+            var dataDirectory = SettingsManager.DataDirectory ?? throw new InvalidOperationException("The data directory is not known yet.");
+            var configDirectory = SettingsManager.ConfigDirectory ?? throw new InvalidOperationException("The configuration directory is not known yet.");
+            var settings = DataBackupSettings.CopyWithoutPluginObjects(settingsManager.ConfigurationData);
+            var settingsJson = JsonSerializer.Serialize(settings, SettingsManager.JSON_OPTIONS);
+            var organizationPluginFolders = DataBackupContents.FindOrganizationPluginsAmongUserPlugins(PluginFactory.AvailablePlugins.OfType<IAvailablePlugin>(), dataDirectory);
+
+            indexCopiesDirectory = await this.CopyIndexesAsync(token);
+
+            var sources = new DataBackupSources(dataDirectory, configDirectory, settingsJson, indexCopiesDirectory, organizationPluginFolders);
+            var manifest = new DataBackupManifest(
+                DataBackupFormat.FORMAT_VERSION,
+                Assembly.GetExecutingAssembly().GetCustomAttribute<MetaDataAttribute>()?.Version ?? "unknown",
+                settings.Version.ToString(),
+                DateTimeOffset.UtcNow,
+                dataDirectory,
+                configDirectory,
+                !string.IsNullOrWhiteSpace(indexCopiesDirectory),
+                []);
+
+            await using var archiveStream = new FileStream(archivePath, FileMode.Create, FileAccess.Write, FileShare.None, BUFFER_SIZE, FileOptions.Asynchronous | FileOptions.SequentialScan);
+            return await DataBackupWriter.WriteAsync(archiveStream, sources, manifest, progress, token);
+        }
+        finally
+        {
+            this.TryDeleteIndexCopies(indexCopiesDirectory);
+        }
+    }
+
     /// <summary>
     /// Whether writing failed since the file system takes no file this large, as FAT32 does beyond 4 GiB.
     /// </summary>

app/MindWork AI Studio/Tools/Services/DataRestoreService.cs

@@ -324,7 +324,8 @@ public sealed class DataRestoreService(ILogger<DataRestoreService> logger, Setti
             var target = this.CreateTarget();
             try
             {
-                DataRestorePreparer.Discard(target);
+                // The unpacked backup may hold thousands of files, and the click to discard it arrives on the thread of the user interface:
+                await Task.Run(() => DataRestorePreparer.Discard(target));
                 logger.LogInformation("Discarded the prepared restore.");
             }
             finally