perf(workspace): optimize large SQL result set mapping and DDL rendering (#334)

lib/core/widgets/virtual_selectable_text_view.dart

@@ -0,0 +1,46 @@
+import 'package:flutter/material.dart' as material;
+
+/// Renders long text efficiently. If line count <= [threshold], uses a single
+/// `SelectableText` inside `SingleChildScrollView` so multi-line selection across
+/// the entire block works seamlessly.
+/// If line count > [threshold], virtualizes lines using `ListView.builder` to
+/// ensure 60 FPS scrolling and rendering without UI jank.
+class VirtualSelectableTextView extends material.StatelessWidget {
+  const VirtualSelectableTextView({
+    super.key,
+    required this.text,
+    this.style,
+    this.threshold = 200,
+    this.padding = const material.EdgeInsets.all(16),
+  });
+
+  final String text;
+  final material.TextStyle? style;
+  final int threshold;
+  final material.EdgeInsets padding;
+
+  @override
+  material.Widget build(material.BuildContext context) {
+    final lines = text.split('\n');
+    if (lines.length <= threshold) {
+      return material.SingleChildScrollView(
+        padding: padding,
+        child: material.SelectableText(
+          text,
+          style: style,
+        ),
+      );
+    }
+
+    return material.ListView.builder(
+      padding: padding,
+      itemCount: lines.length,
+      itemBuilder: (context, index) {
+        return material.SelectableText(
+          lines[index],
+          style: style,
+        );
+      },
+    );
+  }
+}

lib/features/main_screen/results_tab.dart

@@ -1,6 +1,7 @@
 import 'dart:async' show unawaited;
 
 import 'package:flutter/material.dart' as material;
+import 'package:querya_desktop/core/widgets/virtual_selectable_text_view.dart';
 import 'package:querya_desktop/features/main_screen/result_grid_view.dart';
 import 'package:querya_desktop/shared/services/data_export_service.dart';
 import 'package:querya_desktop/shared/widgets/widgets.dart';
@@ -32,15 +33,12 @@ class ResultsTab extends StatelessWidget {
       );
     }
     if (errorMessage != null && errorMessage!.isNotEmpty) {
-      return material.SingleChildScrollView(
-        padding: const material.EdgeInsets.all(16),
-        child: material.SelectableText(
-          errorMessage!,
-          style: material.TextStyle(
-            fontFamily: 'monospace',
-            fontSize: 12,
-            color: Theme.of(context).colorScheme.destructive,
-          ),
+      return VirtualSelectableTextView(
+        text: errorMessage!,
+        style: material.TextStyle(
+          fontFamily: 'monospace',
+          fontSize: 12,
+          color: Theme.of(context).colorScheme.destructive,
         ),
       );
     }

lib/features/mysql/mysql_routine_view.dart

@@ -1,6 +1,7 @@
 import 'package:flutter/material.dart' as material;
 import 'package:querya_desktop/core/database/mysql_service.dart';
 import 'package:querya_desktop/core/storage/local_db.dart';
+import 'package:querya_desktop/core/widgets/virtual_selectable_text_view.dart';
 import 'package:querya_desktop/shared/widgets/widgets.dart';
 
 /// Displays MySQL routine DDL (`SHOW CREATE PROCEDURE` / `SHOW CREATE FUNCTION`).
@@ -165,23 +166,18 @@ class _MysqlRoutineViewState extends material.State<MysqlRoutineView> {
           )
         else if (_error != null)
           material.Expanded(
-            child: material.Center(
-              child: material.SelectableText(
-                _error!,
-                style: material.TextStyle(color: cs.destructive, fontSize: 13),
-              ),
+            child: VirtualSelectableTextView(
+              text: _error!,
+              style: material.TextStyle(color: cs.destructive, fontSize: 13),
             ),
           )
         else
           material.Expanded(
-            child: material.SingleChildScrollView(
-              padding: const material.EdgeInsets.all(16),
-              child: material.SelectableText(
-                _ddlText ?? '',
-                style: const material.TextStyle(
-                  fontFamily: 'monospace',
-                  fontSize: 13,
-                ),
+            child: VirtualSelectableTextView(
+              text: _ddlText ?? '',
+              style: const material.TextStyle(
+                fontFamily: 'monospace',
+                fontSize: 13,
               ),
             ),
           ),

lib/features/mysql/mysql_sql_workspace.dart

@@ -207,10 +207,10 @@ class _MysqlSqlWorkspaceState extends material.State<MysqlSqlWorkspace> {
         n++;
       }
 
-      final outRows = await compute(
-        convertMysqlResultRowsToStrings,
-        MysqlResultConvertJob(rowValues: rawRows),
-      );
+      final job = MysqlResultConvertJob(rowValues: rawRows);
+      final outRows = rawRows.length > 500
+          ? await compute(convertMysqlResultRowsToStrings, job)
+          : convertMysqlResultRowsToStrings(job);
 
       int? affected;
       if (cols.isEmpty && outRows.isEmpty) {

lib/features/postgresql/postgres_result_utils.dart

@@ -0,0 +1,19 @@
+/// Serializable row batch for [convertPostgresResultRowsToStrings] in a worker isolate.
+class PostgresResultConvertJob {
+  const PostgresResultConvertJob({
+    required this.rowValues,
+  });
+
+  final List<List<Object?>> rowValues;
+}
+
+/// Converts PostgreSQL result cell values to display strings off the UI thread.
+List<List<String>> convertPostgresResultRowsToStrings(PostgresResultConvertJob job) {
+  return job.rowValues
+      .map(
+        (row) => row
+            .map((value) => value == null ? 'NULL' : value.toString())
+            .toList(),
+      )
+      .toList();
+}

lib/features/postgresql/postgres_routine_view.dart

@@ -2,6 +2,7 @@ import 'package:flutter/material.dart' as material;
 import 'package:querya_desktop/core/database/postgres_connection.dart';
 import 'package:querya_desktop/core/database/postgres_service.dart';
 import 'package:querya_desktop/core/storage/local_db.dart';
+import 'package:querya_desktop/core/widgets/virtual_selectable_text_view.dart';
 import 'package:querya_desktop/shared/widgets/widgets.dart';
 
 /// Shows [pg_get_functiondef] for each overload of a PostgreSQL function.
@@ -243,8 +244,9 @@ class _PostgresRoutineViewState extends material.State<PostgresRoutineView> {
                             color: cs.border.withValues(alpha: 0.4),
                           ),
                         ),
-                        child: material.SelectableText(
-                          _overloads[i].definition,
+                        child: VirtualSelectableTextView(
+                          text: _overloads[i].definition,
+                          padding: material.EdgeInsets.zero,
                           style: material.TextStyle(
                             fontFamily: 'monospace',
                             fontSize: 12,

lib/features/postgresql/postgres_sql_workspace.dart

@@ -1,9 +1,11 @@
 import 'dart:async';
 import 'dart:io';
 
+import 'package:flutter/foundation.dart' show compute;
 import 'package:flutter/material.dart' as material;
 import 'package:flutter/services.dart' show LogicalKeyboardKey;
 import 'package:file_selector/file_selector.dart';
+import 'package:querya_desktop/features/postgresql/postgres_result_utils.dart';
 import 'package:querya_desktop/core/actions/sql_editor_actions.dart';
 import 'package:querya_desktop/core/actions/sql_editor_command_bridge.dart';
 import 'package:postgres/postgres.dart' as pg;
@@ -348,15 +350,20 @@ class _PostgresSqlWorkspaceState extends material.State<PostgresSqlWorkspace> {
         );
       }
 
-      final outRows = <List<String>>[];
+      final rawRows = <List<Object?>>[];
       var n = 0;
       final cap = _resultMaxRows;
       for (final row in result) {
         if (n >= cap) break;
-        outRows.add(row.map(_cellText).toList());
+        rawRows.add(row.toList());
         n++;
       }
 
+      final job = PostgresResultConvertJob(rowValues: rawRows);
+      final outRows = rawRows.length > 500
+          ? await compute(convertPostgresResultRowsToStrings, job)
+          : convertPostgresResultRowsToStrings(job);
+
       setState(() {
         _columns = cols;
         _rows = outRows;
@@ -410,11 +417,6 @@ class _PostgresSqlWorkspaceState extends material.State<PostgresSqlWorkspace> {
     }
   }
 
-  static String _cellText(Object? v) {
-    if (v == null) return 'NULL';
-    return v.toString();
-  }
-
   Future<void> _openSqlFile() async {
     try {
       final file = await openFile(

lib/features/sqlite/sqlite_result_utils.dart

@@ -0,0 +1,19 @@
+/// Serializable row batch for [convertSqliteResultRowsToStrings] in a worker isolate.
+class SqliteResultConvertJob {
+  const SqliteResultConvertJob({
+    required this.rowValues,
+  });
+
+  final List<List<Object?>> rowValues;
+}
+
+/// Converts SQLite result cell values to display strings off the UI thread.
+List<List<String>> convertSqliteResultRowsToStrings(SqliteResultConvertJob job) {
+  return job.rowValues
+      .map(
+        (row) => row
+            .map((value) => value == null ? 'NULL' : value.toString())
+            .toList(),
+      )
+      .toList();
+}

lib/features/sqlite/sqlite_sql_workspace.dart

@@ -1,8 +1,10 @@
 import 'dart:async';
 import 'dart:io';
+import 'package:flutter/foundation.dart' show compute;
 import 'package:flutter/material.dart' as material;
 import 'package:flutter/services.dart' show LogicalKeyboardKey;
 import 'package:file_selector/file_selector.dart';
+import 'package:querya_desktop/features/sqlite/sqlite_result_utils.dart';
 import 'package:querya_desktop/core/actions/sql_editor_actions.dart';
 import 'package:querya_desktop/core/actions/sql_editor_command_bridge.dart';
 import 'package:querya_desktop/core/database/sqlite_service.dart';
@@ -167,14 +169,15 @@ class _SqliteSqlWorkspaceState extends material.State<SqliteSqlWorkspace> {
       final truncated = results.length > cap;
       final limitCount = truncated ? cap : results.length;
 
-      final rawRows = results.take(limitCount).toList();
-      final outRows = rawRows.map((row) {
-        return cols.map((col) {
-          final val = row[col];
-          return val == null ? 'NULL' : val.toString();
-        }).toList();
+      final rawRows = results.take(limitCount).map((row) {
+        return cols.map((col) => row[col]).toList();
       }).toList();
 
+      final job = SqliteResultConvertJob(rowValues: rawRows);
+      final outRows = rawRows.length > 500
+          ? await compute(convertSqliteResultRowsToStrings, job)
+          : convertSqliteResultRowsToStrings(job);
+
       setState(() {
         _columns = cols;
         _rows = outRows;

test/core/widgets/virtual_selectable_text_view_test.dart

@@ -0,0 +1,44 @@
+import 'package:flutter/material.dart' as material;
+import 'package:flutter_test/flutter_test.dart';
+import 'package:querya_desktop/core/widgets/virtual_selectable_text_view.dart';
+
+void main() {
+  group('VirtualSelectableTextView', () {
+    testWidgets('renders SingleChildScrollView + SelectableText below threshold', (tester) async {
+      const text = 'line 1\nline 2\nline 3';
+      await tester.pumpWidget(
+        const material.MaterialApp(
+          home: material.Scaffold(
+            body: VirtualSelectableTextView(
+              text: text,
+              threshold: 10,
+            ),
+          ),
+        ),
+      );
+
+      expect(find.byType(material.SingleChildScrollView), findsOneWidget);
+      expect(find.byType(material.ListView), findsNothing);
+      expect(find.text(text), findsOneWidget);
+    });
+
+    testWidgets('renders ListView.builder above threshold', (tester) async {
+      final text = List.generate(50, (i) => 'Virtual Line $i').join('\n');
+      await tester.pumpWidget(
+        material.MaterialApp(
+          home: material.Scaffold(
+            body: VirtualSelectableTextView(
+              text: text,
+              threshold: 10,
+            ),
+          ),
+        ),
+      );
+
+      expect(find.byType(material.SingleChildScrollView), findsNothing);
+      expect(find.byType(material.ListView), findsOneWidget);
+      expect(find.text('Virtual Line 0'), findsOneWidget);
+      expect(find.text('Virtual Line 1'), findsOneWidget);
+    });
+  });
+}

test/features/sql_workspaces/result_conversion_perf_test.dart

@@ -0,0 +1,66 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:querya_desktop/features/mysql/mysql_result_utils.dart';
+import 'package:querya_desktop/features/postgresql/postgres_result_utils.dart';
+import 'package:querya_desktop/features/sqlite/sqlite_result_utils.dart';
+
+void main() {
+  group('Result Conversion Job & Utilities', () {
+    test('convertMysqlResultRowsToStrings maps nulls and primitives correctly', () {
+      final rawRows = [
+        [1, 'hello', null, 3.14, true],
+        [2, 'world', 'abc', null, false],
+      ];
+      final job = MysqlResultConvertJob(rowValues: rawRows);
+      final out = convertMysqlResultRowsToStrings(job);
+
+      expect(out.length, 2);
+      expect(out[0], ['1', 'hello', 'NULL', '3.14', 'true']);
+      expect(out[1], ['2', 'world', 'abc', 'NULL', 'false']);
+    });
+
+    test('convertPostgresResultRowsToStrings maps nulls and primitives correctly', () {
+      final rawRows = [
+        [100, null, 'pg_test'],
+        [null, 999, 'foo'],
+      ];
+      final job = PostgresResultConvertJob(rowValues: rawRows);
+      final out = convertPostgresResultRowsToStrings(job);
+
+      expect(out.length, 2);
+      expect(out[0], ['100', 'NULL', 'pg_test']);
+      expect(out[1], ['NULL', '999', 'foo']);
+    });
+
+    test('convertSqliteResultRowsToStrings maps nulls and primitives correctly', () {
+      final rawRows = [
+        ['sqlite', null, 42],
+        [null, null, null],
+      ];
+      final job = SqliteResultConvertJob(rowValues: rawRows);
+      final out = convertSqliteResultRowsToStrings(job);
+
+      expect(out.length, 2);
+      expect(out[0], ['sqlite', 'NULL', '42']);
+      expect(out[1], ['NULL', 'NULL', 'NULL']);
+    });
+
+    test('All convert jobs handle large batches efficiently', () {
+      final rawBatch = List.generate(
+        2000,
+        (r) => List.generate(15, (c) => c % 3 == 0 ? null : 'row_${r}_col_$c'),
+      );
+
+      final pgJob = PostgresResultConvertJob(rowValues: rawBatch);
+      final pgOut = convertPostgresResultRowsToStrings(pgJob);
+      expect(pgOut.length, 2000);
+      expect(pgOut.first[0], 'NULL');
+      expect(pgOut.first[1], 'row_0_col_1');
+
+      final sqliteJob = SqliteResultConvertJob(rowValues: rawBatch);
+      final sqliteOut = convertSqliteResultRowsToStrings(sqliteJob);
+      expect(sqliteOut.length, 2000);
+      expect(sqliteOut[100][0], 'NULL');
+      expect(sqliteOut[100][1], 'row_100_col_1');
+    });
+  });
+}