Support drift-defined views schema tools (#1813)

drift_dev/lib/src/services/schema/schema_files.dart

@@ -60,6 +60,22 @@ class SchemaWriter {
         'name': entity.name,
         'sql': entity.createStmt,
       };
+    } else if (entity is MoorView) {
+      if (entity.declaration is! MoorViewDeclaration) {
+        throw UnsupportedError(
+            'Exporting Dart-defined views into a schema is not '
+            'currently supported');
+      }
+
+      type = 'view';
+      data = {
+        'name': entity.name,
+        'sql': entity
+            .createSql(const MoorOptions.defaults(newSqlCodeGeneration: true)),
+        'dart_data_name': entity.dartTypeName,
+        'dart_info_name': entity.entityInfoName,
+        'columns': [for (final column in entity.columns) _columnData(column)],
+      };
     } else if (entity is SpecialQuery) {
       type = 'special-query';
       data = {
@@ -200,6 +216,9 @@ class SchemaReader {
       case 'table':
         entity = _readTable(content);
         break;
+      case 'view':
+        entity = _readView(content);
+        break;
       case 'special-query':
         // Not relevant for the schema.
         return;
@@ -284,6 +303,18 @@ class SchemaReader {
     );
   }
 
+  MoorView _readView(Map<String, dynamic> content) {
+    return MoorView(
+      declaration: null,
+      name: content['name'] as String,
+      dartTypeName: content['dart_data_name'] as String,
+      entityInfoName: content['dart_info_name'] as String,
+    )..columns = [
+        for (final column in content['columns'])
+          _readColumn(column as Map<String, dynamic>)
+      ];
+  }
+
   MoorColumn _readColumn(Map<String, dynamic> data) {
     final name = data['name'] as String;
     final moorType = ColumnType.values

drift_dev/test/services/schema/writer_test.dart

@@ -40,6 +40,8 @@ CREATE TRIGGER delete_empty_groups AFTER DELETE ON group_members BEGIN
 END;
 
 CREATE INDEX groups_name ON "groups"(name);
+
+CREATE VIEW my_view AS SELECT id FROM "groups";
       ''',
       'foo|lib/main.dart': '''
 import 'package:drift/drift.dart';
@@ -281,6 +283,33 @@ const expected = r'''
         },
         {
             "id": 5,
+            "references": [
+                0
+            ],
+            "type": "view",
+            "data": {
+                "name": "my_view",
+                "sql": "CREATE VIEW my_view AS SELECT id FROM \"groups\"",
+                "dart_data_name": "MyViewData",
+                "dart_info_name": "MyView",
+                "columns": [
+                    {
+                        "name": "id",
+                        "getter_name": "id",
+                        "moor_type": "ColumnType.integer",
+                        "nullable": false,
+                        "customConstraints": null,
+                        "default_dart": null,
+                        "default_client_dart": null,
+                        "dsl_features": [
+
+                        ]
+                    }
+                ]
+            }
+        },
+        {
+            "id": 6,
             "references": [
 
             ],

examples/migrations_example/drift_migrations/drift_schema_v5.json

@@ -1 +1 @@
-{"_meta":{"description":"This file contains a serialized version of schema entities for moor.","version":"0.1.0-dev-preview"},"entities":[{"id":0,"references":[],"type":"table","data":{"name":"users","was_declared_in_moor":false,"columns":[{"name":"id","getter_name":"id","moor_type":"ColumnType.integer","nullable":false,"customConstraints":null,"defaultConstraints":"PRIMARY KEY AUTOINCREMENT","default_dart":null,"default_client_dart":null,"dsl_features":["auto-increment","primary-key"]},{"name":"name","getter_name":"name","moor_type":"ColumnType.text","nullable":false,"customConstraints":null,"default_dart":"const Constant('name')","default_client_dart":null,"dsl_features":[]},{"name":"next_user","getter_name":"nextUser","moor_type":"ColumnType.integer","nullable":true,"customConstraints":null,"defaultConstraints":"REFERENCES users (id)","default_dart":null,"default_client_dart":null,"dsl_features":["unknown"]}],"is_virtual":false}},{"id":1,"references":[0],"type":"table","data":{"name":"groups","was_declared_in_moor":true,"columns":[{"name":"id","getter_name":"id","moor_type":"ColumnType.integer","nullable":false,"customConstraints":"NOT NULL","default_dart":null,"default_client_dart":null,"dsl_features":[]},{"name":"title","getter_name":"title","moor_type":"ColumnType.text","nullable":false,"customConstraints":"NOT NULL","default_dart":null,"default_client_dart":null,"dsl_features":[]},{"name":"deleted","getter_name":"deleted","moor_type":"ColumnType.boolean","nullable":true,"customConstraints":"DEFAULT FALSE","default_dart":"const CustomExpression<bool>('FALSE')","default_client_dart":null,"dsl_features":[]},{"name":"owner","getter_name":"owner","moor_type":"ColumnType.integer","nullable":false,"customConstraints":"NOT NULL REFERENCES users (id)","default_dart":null,"default_client_dart":null,"dsl_features":[]}],"is_virtual":false,"constraints":["PRIMARY KEY (id)"],"explicit_pk":["id"]}}]}
+{"_meta":{"description":"This file contains a serialized version of schema entities for moor.","version":"0.1.0-dev-preview"},"entities":[{"id":0,"references":[],"type":"table","data":{"name":"users","was_declared_in_moor":false,"columns":[{"name":"id","getter_name":"id","moor_type":"ColumnType.integer","nullable":false,"customConstraints":null,"defaultConstraints":"PRIMARY KEY AUTOINCREMENT","default_dart":null,"default_client_dart":null,"dsl_features":["auto-increment","primary-key"]},{"name":"name","getter_name":"name","moor_type":"ColumnType.text","nullable":false,"customConstraints":null,"default_dart":"const Constant('name')","default_client_dart":null,"dsl_features":[]},{"name":"next_user","getter_name":"nextUser","moor_type":"ColumnType.integer","nullable":true,"customConstraints":null,"defaultConstraints":"REFERENCES users (id)","default_dart":null,"default_client_dart":null,"dsl_features":["unknown"]}],"is_virtual":false}},{"id":1,"references":[0],"type":"table","data":{"name":"groups","was_declared_in_moor":true,"columns":[{"name":"id","getter_name":"id","moor_type":"ColumnType.integer","nullable":false,"customConstraints":"NOT NULL","default_dart":null,"default_client_dart":null,"dsl_features":[]},{"name":"title","getter_name":"title","moor_type":"ColumnType.text","nullable":false,"customConstraints":"NOT NULL","default_dart":null,"default_client_dart":null,"dsl_features":[]},{"name":"deleted","getter_name":"deleted","moor_type":"ColumnType.boolean","nullable":true,"customConstraints":"DEFAULT FALSE","default_dart":"const CustomExpression<bool>('FALSE')","default_client_dart":null,"dsl_features":[]},{"name":"owner","getter_name":"owner","moor_type":"ColumnType.integer","nullable":false,"customConstraints":"NOT NULL REFERENCES users (id)","default_dart":null,"default_client_dart":null,"dsl_features":[]}],"is_virtual":false,"constraints":["PRIMARY KEY (id)"],"explicit_pk":["id"]}},{"id":2,"references":[1,0],"type":"view","data":{"name":"group_count","sql":"CREATE VIEW group_count AS SELECT users.*, (SELECT COUNT(*) FROM \"groups\" WHERE owner = users.id) AS group_count FROM users","dart_data_name":"GroupCountData","dart_info_name":"GroupCount","columns":[{"name":"id","getter_name":"id","moor_type":"ColumnType.integer","nullable":false,"customConstraints":null,"default_dart":null,"default_client_dart":null,"dsl_features":[]},{"name":"name","getter_name":"name","moor_type":"ColumnType.text","nullable":false,"customConstraints":null,"default_dart":null,"default_client_dart":null,"dsl_features":[]},{"name":"next_user","getter_name":"nextUser","moor_type":"ColumnType.integer","nullable":true,"customConstraints":null,"default_dart":null,"default_client_dart":null,"dsl_features":[]},{"name":"group_count","getter_name":"groupCount","moor_type":"ColumnType.integer","nullable":false,"customConstraints":null,"default_dart":null,"default_client_dart":null,"dsl_features":[]}]}}]}

examples/migrations_example/lib/database.dart

@@ -44,6 +44,9 @@ class Database extends _$Database {
           } else if (target == 5) {
             // Just add a new column that was added in version 5;
             await m.addColumn(users, users.nextUser);
+
+            // And create the view on users
+            await m.createView(groupCount);
           }
         }
       },

examples/migrations_example/lib/database.g.dart

@@ -204,8 +204,6 @@ class $UsersTable extends Users with TableInfo<$UsersTable, User> {
   @override
   Set<GeneratedColumn> get $primaryKey => {id};
   @override
-  List<Set<GeneratedColumn>> get uniqueKeys => [];
-  @override
   User map(Map<String, dynamic> data, {String? tablePrefix}) {
     return User.fromData(data,
         prefix: tablePrefix != null ? '$tablePrefix.' : null);
@@ -454,8 +452,6 @@ class Groups extends Table with TableInfo<Groups, Group> {
   @override
   Set<GeneratedColumn> get $primaryKey => {id};
   @override
-  List<Set<GeneratedColumn>> get uniqueKeys => [];
-  @override
   Group map(Map<String, dynamic> data, {String? tablePrefix}) {
     return Group.fromData(data,
         prefix: tablePrefix != null ? '$tablePrefix.' : null);
@@ -472,13 +468,135 @@ class Groups extends Table with TableInfo<Groups, Group> {
   bool get dontWriteConstraints => true;
 }
 
+class GroupCountData extends DataClass {
+  final int id;
+  final String name;
+  final int? nextUser;
+  final int groupCount;
+  GroupCountData(
+      {required this.id,
+      required this.name,
+      this.nextUser,
+      required this.groupCount});
+  factory GroupCountData.fromData(Map<String, dynamic> data, {String? prefix}) {
+    final effectivePrefix = prefix ?? '';
+    return GroupCountData(
+      id: const IntType()
+          .mapFromDatabaseResponse(data['${effectivePrefix}id'])!,
+      name: const StringType()
+          .mapFromDatabaseResponse(data['${effectivePrefix}name'])!,
+      nextUser: const IntType()
+          .mapFromDatabaseResponse(data['${effectivePrefix}next_user']),
+      groupCount: const IntType()
+          .mapFromDatabaseResponse(data['${effectivePrefix}group_count'])!,
+    );
+  }
+  factory GroupCountData.fromJson(Map<String, dynamic> json,
+      {ValueSerializer? serializer}) {
+    serializer ??= driftRuntimeOptions.defaultSerializer;
+    return GroupCountData(
+      id: serializer.fromJson<int>(json['id']),
+      name: serializer.fromJson<String>(json['name']),
+      nextUser: serializer.fromJson<int?>(json['nextUser']),
+      groupCount: serializer.fromJson<int>(json['groupCount']),
+    );
+  }
+  @override
+  Map<String, dynamic> toJson({ValueSerializer? serializer}) {
+    serializer ??= driftRuntimeOptions.defaultSerializer;
+    return <String, dynamic>{
+      'id': serializer.toJson<int>(id),
+      'name': serializer.toJson<String>(name),
+      'nextUser': serializer.toJson<int?>(nextUser),
+      'groupCount': serializer.toJson<int>(groupCount),
+    };
+  }
+
+  GroupCountData copyWith(
+          {int? id, String? name, int? nextUser, int? groupCount}) =>
+      GroupCountData(
+        id: id ?? this.id,
+        name: name ?? this.name,
+        nextUser: nextUser ?? this.nextUser,
+        groupCount: groupCount ?? this.groupCount,
+      );
+  @override
+  String toString() {
+    return (StringBuffer('GroupCountData(')
+          ..write('id: $id, ')
+          ..write('name: $name, ')
+          ..write('nextUser: $nextUser, ')
+          ..write('groupCount: $groupCount')
+          ..write(')'))
+        .toString();
+  }
+
+  @override
+  int get hashCode => Object.hash(id, name, nextUser, groupCount);
+  @override
+  bool operator ==(Object other) =>
+      identical(this, other) ||
+      (other is GroupCountData &&
+          other.id == this.id &&
+          other.name == this.name &&
+          other.nextUser == this.nextUser &&
+          other.groupCount == this.groupCount);
+}
+
+class GroupCount extends ViewInfo<GroupCount, GroupCountData>
+    implements HasResultSet {
+  final String? _alias;
+  @override
+  final _$Database attachedDatabase;
+  GroupCount(this.attachedDatabase, [this._alias]);
+  @override
+  List<GeneratedColumn> get $columns => [id, name, nextUser, groupCount];
+  @override
+  String get aliasedName => _alias ?? entityName;
+  @override
+  String get entityName => 'group_count';
+  @override
+  String get createViewStmt =>
+      'CREATE VIEW group_count AS SELECT\n    users.*,\n    (SELECT COUNT(*) FROM "groups" WHERE owner = users.id) AS group_count\n  FROM users;';
+  @override
+  GroupCount get asDslTable => this;
+  @override
+  GroupCountData map(Map<String, dynamic> data, {String? tablePrefix}) {
+    return GroupCountData.fromData(data,
+        prefix: tablePrefix != null ? '$tablePrefix.' : null);
+  }
+
+  late final GeneratedColumn<int?> id =
+      GeneratedColumn<int?>('id', aliasedName, false, type: const IntType());
+  late final GeneratedColumn<String?> name = GeneratedColumn<String?>(
+      'name', aliasedName, false,
+      type: const StringType());
+  late final GeneratedColumn<int?> nextUser = GeneratedColumn<int?>(
+      'next_user', aliasedName, true,
+      type: const IntType());
+  late final GeneratedColumn<int?> groupCount = GeneratedColumn<int?>(
+      'group_count', aliasedName, false,
+      type: const IntType());
+  @override
+  GroupCount createAlias(String alias) {
+    return GroupCount(attachedDatabase, alias);
+  }
+
+  @override
+  Query? get query => null;
+  @override
+  Set<String> get readTables => const {'groups', 'users'};
+}
+
 abstract class _$Database extends GeneratedDatabase {
   _$Database(QueryExecutor e) : super(SqlTypeSystem.defaultInstance, e);
   _$Database.connect(DatabaseConnection c) : super.connect(c);
   late final $UsersTable users = $UsersTable(this);
   late final Groups groups = Groups(this);
+  late final GroupCount groupCount = GroupCount(this);
   @override
   Iterable<TableInfo> get allTables => allSchemaEntities.whereType<TableInfo>();
   @override
-  List<DatabaseSchemaEntity> get allSchemaEntities => [users, groups];
+  List<DatabaseSchemaEntity> get allSchemaEntities =>
+      [users, groups, groupCount];
 }

examples/migrations_example/lib/src/generated/schema_v1.dart

@@ -21,8 +21,6 @@ class Users extends Table with TableInfo {
   @override
   Set<GeneratedColumn> get $primaryKey => {id};
   @override
-  List<Set<GeneratedColumn>> get uniqueKeys => [];
-  @override
   Never map(Map<String, dynamic> data, {String? tablePrefix}) {
     throw UnsupportedError('TableInfo.map in schema verification code');
   }

examples/migrations_example/lib/src/generated/schema_v2.dart

@@ -24,8 +24,6 @@ class Users extends Table with TableInfo {
   @override
   Set<GeneratedColumn> get $primaryKey => {id};
   @override
-  List<Set<GeneratedColumn>> get uniqueKeys => [];
-  @override
   Never map(Map<String, dynamic> data, {String? tablePrefix}) {
     throw UnsupportedError('TableInfo.map in schema verification code');
   }

examples/migrations_example/lib/src/generated/schema_v3.dart

@@ -24,8 +24,6 @@ class Users extends Table with TableInfo {
   @override
   Set<GeneratedColumn> get $primaryKey => {id};
   @override
-  List<Set<GeneratedColumn>> get uniqueKeys => [];
-  @override
   Never map(Map<String, dynamic> data, {String? tablePrefix}) {
     throw UnsupportedError('TableInfo.map in schema verification code');
   }
@@ -74,8 +72,6 @@ class Groups extends Table with TableInfo {
   @override
   Set<GeneratedColumn> get $primaryKey => {id};
   @override
-  List<Set<GeneratedColumn>> get uniqueKeys => [];
-  @override
   Never map(Map<String, dynamic> data, {String? tablePrefix}) {
     throw UnsupportedError('TableInfo.map in schema verification code');
   }

examples/migrations_example/lib/src/generated/schema_v4.dart

@@ -26,8 +26,6 @@ class Users extends Table with TableInfo {
   @override
   Set<GeneratedColumn> get $primaryKey => {id};
   @override
-  List<Set<GeneratedColumn>> get uniqueKeys => [];
-  @override
   Never map(Map<String, dynamic> data, {String? tablePrefix}) {
     throw UnsupportedError('TableInfo.map in schema verification code');
   }
@@ -76,8 +74,6 @@ class Groups extends Table with TableInfo {
   @override
   Set<GeneratedColumn> get $primaryKey => {id};
   @override
-  List<Set<GeneratedColumn>> get uniqueKeys => [];
-  @override
   Never map(Map<String, dynamic> data, {String? tablePrefix}) {
     throw UnsupportedError('TableInfo.map in schema verification code');
   }

examples/migrations_example/lib/src/generated/schema_v5.dart

@@ -31,8 +31,6 @@ class Users extends Table with TableInfo {
   @override
   Set<GeneratedColumn> get $primaryKey => {id};
   @override
-  List<Set<GeneratedColumn>> get uniqueKeys => [];
-  @override
   Never map(Map<String, dynamic> data, {String? tablePrefix}) {
     throw UnsupportedError('TableInfo.map in schema verification code');
   }
@@ -81,8 +79,6 @@ class Groups extends Table with TableInfo {
   @override
   Set<GeneratedColumn> get $primaryKey => {id};
   @override
-  List<Set<GeneratedColumn>> get uniqueKeys => [];
-  @override
   Never map(Map<String, dynamic> data, {String? tablePrefix}) {
     throw UnsupportedError('TableInfo.map in schema verification code');
   }
@@ -98,15 +94,59 @@ class Groups extends Table with TableInfo {
   bool get dontWriteConstraints => true;
 }
 
+class GroupCount extends ViewInfo<GroupCount, Never> implements HasResultSet {
+  final String? _alias;
+  @override
+  final DatabaseAtV5 attachedDatabase;
+  GroupCount(this.attachedDatabase, [this._alias]);
+  @override
+  List<GeneratedColumn> get $columns => [id, name, nextUser, groupCount];
+  @override
+  String get aliasedName => _alias ?? entityName;
+  @override
+  String get entityName => 'group_count';
+  @override
+  String? get createViewStmt => null;
+  @override
+  GroupCount get asDslTable => this;
+  @override
+  Never map(Map<String, dynamic> data, {String? tablePrefix}) {
+    throw UnsupportedError('TableInfo.map in schema verification code');
+  }
+
+  late final GeneratedColumn<int?> id =
+      GeneratedColumn<int?>('id', aliasedName, false, type: const IntType());
+  late final GeneratedColumn<String?> name = GeneratedColumn<String?>(
+      'name', aliasedName, false,
+      type: const StringType());
+  late final GeneratedColumn<int?> nextUser = GeneratedColumn<int?>(
+      'next_user', aliasedName, true,
+      type: const IntType());
+  late final GeneratedColumn<int?> groupCount = GeneratedColumn<int?>(
+      'group_count', aliasedName, false,
+      type: const IntType());
+  @override
+  GroupCount createAlias(String alias) {
+    return GroupCount(attachedDatabase, alias);
+  }
+
+  @override
+  Query? get query => null;
+  @override
+  Set<String> get readTables => const {};
+}
+
 class DatabaseAtV5 extends GeneratedDatabase {
   DatabaseAtV5(QueryExecutor e) : super(SqlTypeSystem.defaultInstance, e);
   DatabaseAtV5.connect(DatabaseConnection c) : super.connect(c);
   late final Users users = Users(this);
   late final Groups groups = Groups(this);
+  late final GroupCount groupCount = GroupCount(this);
   @override
   Iterable<TableInfo> get allTables => allSchemaEntities.whereType<TableInfo>();
   @override
-  List<DatabaseSchemaEntity> get allSchemaEntities => [users, groups];
+  List<DatabaseSchemaEntity> get allSchemaEntities =>
+      [users, groups, groupCount];
   @override
   int get schemaVersion => 5;
 }

examples/migrations_example/lib/tables.drift

@@ -8,4 +8,10 @@ CREATE TABLE "groups" (
     owner INTEGER NOT NULL REFERENCES users (id),
 
     PRIMARY KEY (id)
-);
+);
+
+-- This view was added in schema version 5
+CREATE VIEW group_count AS SELECT
+    users.*,
+    (SELECT COUNT(*) FROM "groups" WHERE owner = users.id) AS group_count
+  FROM users;

examples/migrations_example/test/generated/schema_v1.dart

@@ -117,8 +117,6 @@ class Users extends Table with TableInfo<Users, UsersData> {
   @override
   Set<GeneratedColumn> get $primaryKey => {id};
   @override
-  List<Set<GeneratedColumn>> get uniqueKeys => [];
-  @override
   UsersData map(Map<String, dynamic> data, {String? tablePrefix}) {
     return UsersData.fromData(data,
         prefix: tablePrefix != null ? '$tablePrefix.' : null);

examples/migrations_example/test/generated/schema_v2.dart

@@ -140,8 +140,6 @@ class Users extends Table with TableInfo<Users, UsersData> {
   @override
   Set<GeneratedColumn> get $primaryKey => {id};
   @override
-  List<Set<GeneratedColumn>> get uniqueKeys => [];
-  @override
   UsersData map(Map<String, dynamic> data, {String? tablePrefix}) {
     return UsersData.fromData(data,
         prefix: tablePrefix != null ? '$tablePrefix.' : null);

examples/migrations_example/test/generated/schema_v3.dart

@@ -140,8 +140,6 @@ class Users extends Table with TableInfo<Users, UsersData> {
   @override
   Set<GeneratedColumn> get $primaryKey => {id};
   @override
-  List<Set<GeneratedColumn>> get uniqueKeys => [];
-  @override
   UsersData map(Map<String, dynamic> data, {String? tablePrefix}) {
     return UsersData.fromData(data,
         prefix: tablePrefix != null ? '$tablePrefix.' : null);
@@ -363,8 +361,6 @@ class Groups extends Table with TableInfo<Groups, GroupsData> {
   @override
   Set<GeneratedColumn> get $primaryKey => {id};
   @override
-  List<Set<GeneratedColumn>> get uniqueKeys => [];
-  @override
   GroupsData map(Map<String, dynamic> data, {String? tablePrefix}) {
     return GroupsData.fromData(data,
         prefix: tablePrefix != null ? '$tablePrefix.' : null);

examples/migrations_example/test/generated/schema_v4.dart

@@ -142,8 +142,6 @@ class Users extends Table with TableInfo<Users, UsersData> {
   @override
   Set<GeneratedColumn> get $primaryKey => {id};
   @override
-  List<Set<GeneratedColumn>> get uniqueKeys => [];
-  @override
   UsersData map(Map<String, dynamic> data, {String? tablePrefix}) {
     return UsersData.fromData(data,
         prefix: tablePrefix != null ? '$tablePrefix.' : null);
@@ -365,8 +363,6 @@ class Groups extends Table with TableInfo<Groups, GroupsData> {
   @override
   Set<GeneratedColumn> get $primaryKey => {id};
   @override
-  List<Set<GeneratedColumn>> get uniqueKeys => [];
-  @override
   GroupsData map(Map<String, dynamic> data, {String? tablePrefix}) {
     return GroupsData.fromData(data,
         prefix: tablePrefix != null ? '$tablePrefix.' : null);

examples/migrations_example/test/generated/schema_v5.dart

@@ -174,8 +174,6 @@ class Users extends Table with TableInfo<Users, UsersData> {
   @override
   Set<GeneratedColumn> get $primaryKey => {id};
   @override
-  List<Set<GeneratedColumn>> get uniqueKeys => [];
-  @override
   UsersData map(Map<String, dynamic> data, {String? tablePrefix}) {
     return UsersData.fromData(data,
         prefix: tablePrefix != null ? '$tablePrefix.' : null);
@@ -397,8 +395,6 @@ class Groups extends Table with TableInfo<Groups, GroupsData> {
   @override
   Set<GeneratedColumn> get $primaryKey => {id};
   @override
-  List<Set<GeneratedColumn>> get uniqueKeys => [];
-  @override
   GroupsData map(Map<String, dynamic> data, {String? tablePrefix}) {
     return GroupsData.fromData(data,
         prefix: tablePrefix != null ? '$tablePrefix.' : null);
@@ -415,15 +411,136 @@ class Groups extends Table with TableInfo<Groups, GroupsData> {
   bool get dontWriteConstraints => true;
 }
 
+class GroupCountData extends DataClass {
+  final int id;
+  final String name;
+  final int? nextUser;
+  final int groupCount;
+  GroupCountData(
+      {required this.id,
+      required this.name,
+      this.nextUser,
+      required this.groupCount});
+  factory GroupCountData.fromData(Map<String, dynamic> data, {String? prefix}) {
+    final effectivePrefix = prefix ?? '';
+    return GroupCountData(
+      id: const IntType()
+          .mapFromDatabaseResponse(data['${effectivePrefix}id'])!,
+      name: const StringType()
+          .mapFromDatabaseResponse(data['${effectivePrefix}name'])!,
+      nextUser: const IntType()
+          .mapFromDatabaseResponse(data['${effectivePrefix}next_user']),
+      groupCount: const IntType()
+          .mapFromDatabaseResponse(data['${effectivePrefix}group_count'])!,
+    );
+  }
+  factory GroupCountData.fromJson(Map<String, dynamic> json,
+      {ValueSerializer? serializer}) {
+    serializer ??= driftRuntimeOptions.defaultSerializer;
+    return GroupCountData(
+      id: serializer.fromJson<int>(json['id']),
+      name: serializer.fromJson<String>(json['name']),
+      nextUser: serializer.fromJson<int?>(json['nextUser']),
+      groupCount: serializer.fromJson<int>(json['groupCount']),
+    );
+  }
+  @override
+  Map<String, dynamic> toJson({ValueSerializer? serializer}) {
+    serializer ??= driftRuntimeOptions.defaultSerializer;
+    return <String, dynamic>{
+      'id': serializer.toJson<int>(id),
+      'name': serializer.toJson<String>(name),
+      'nextUser': serializer.toJson<int?>(nextUser),
+      'groupCount': serializer.toJson<int>(groupCount),
+    };
+  }
+
+  GroupCountData copyWith(
+          {int? id, String? name, int? nextUser, int? groupCount}) =>
+      GroupCountData(
+        id: id ?? this.id,
+        name: name ?? this.name,
+        nextUser: nextUser ?? this.nextUser,
+        groupCount: groupCount ?? this.groupCount,
+      );
+  @override
+  String toString() {
+    return (StringBuffer('GroupCountData(')
+          ..write('id: $id, ')
+          ..write('name: $name, ')
+          ..write('nextUser: $nextUser, ')
+          ..write('groupCount: $groupCount')
+          ..write(')'))
+        .toString();
+  }
+
+  @override
+  int get hashCode => Object.hash(id, name, nextUser, groupCount);
+  @override
+  bool operator ==(Object other) =>
+      identical(this, other) ||
+      (other is GroupCountData &&
+          other.id == this.id &&
+          other.name == this.name &&
+          other.nextUser == this.nextUser &&
+          other.groupCount == this.groupCount);
+}
+
+class GroupCount extends ViewInfo<GroupCount, GroupCountData>
+    implements HasResultSet {
+  final String? _alias;
+  @override
+  final DatabaseAtV5 attachedDatabase;
+  GroupCount(this.attachedDatabase, [this._alias]);
+  @override
+  List<GeneratedColumn> get $columns => [id, name, nextUser, groupCount];
+  @override
+  String get aliasedName => _alias ?? entityName;
+  @override
+  String get entityName => 'group_count';
+  @override
+  String? get createViewStmt => null;
+  @override
+  GroupCount get asDslTable => this;
+  @override
+  GroupCountData map(Map<String, dynamic> data, {String? tablePrefix}) {
+    return GroupCountData.fromData(data,
+        prefix: tablePrefix != null ? '$tablePrefix.' : null);
+  }
+
+  late final GeneratedColumn<int?> id =
+      GeneratedColumn<int?>('id', aliasedName, false, type: const IntType());
+  late final GeneratedColumn<String?> name = GeneratedColumn<String?>(
+      'name', aliasedName, false,
+      type: const StringType());
+  late final GeneratedColumn<int?> nextUser = GeneratedColumn<int?>(
+      'next_user', aliasedName, true,
+      type: const IntType());
+  late final GeneratedColumn<int?> groupCount = GeneratedColumn<int?>(
+      'group_count', aliasedName, false,
+      type: const IntType());
+  @override
+  GroupCount createAlias(String alias) {
+    return GroupCount(attachedDatabase, alias);
+  }
+
+  @override
+  Query? get query => null;
+  @override
+  Set<String> get readTables => const {};
+}
+
 class DatabaseAtV5 extends GeneratedDatabase {
   DatabaseAtV5(QueryExecutor e) : super(SqlTypeSystem.defaultInstance, e);
   DatabaseAtV5.connect(DatabaseConnection c) : super.connect(c);
   late final Users users = Users(this);
   late final Groups groups = Groups(this);
+  late final GroupCount groupCount = GroupCount(this);
   @override
   Iterable<TableInfo> get allTables => allSchemaEntities.whereType<TableInfo>();
   @override
-  List<DatabaseSchemaEntity> get allSchemaEntities => [users, groups];
+  List<DatabaseSchemaEntity> get allSchemaEntities =>
+      [users, groups, groupCount];
   @override
   int get schemaVersion => 5;
 }

examples/migrations_example/test/migration_test.dart

@@ -8,6 +8,8 @@ import 'generated/schema.dart';
 
 import 'generated/schema_v1.dart' as v1;
 import 'generated/schema_v2.dart' as v2;
+import 'generated/schema_v4.dart' as v4;
+import 'generated/schema_v5.dart' as v5;
 
 void main() {
   driftRuntimeOptions.dontWarnAboutMultipleDatabases = true;
@@ -61,4 +63,39 @@ void main() {
     await verifier.migrateAndValidate(db, 5);
     await db.close();
   });
+
+  test('view works after upgrade from v4 to v5', () async {
+    final schema = await verifier.schemaAt(4);
+
+    final oldDb = v4.DatabaseAtV4.connect(schema.newConnection());
+    await oldDb.batch((batch) {
+      batch
+        ..insert(oldDb.users, v4.UsersCompanion.insert(id: Value(1)))
+        ..insert(oldDb.users, v4.UsersCompanion.insert(id: Value(2)))
+        ..insert(
+            oldDb.groups, v4.GroupsCompanion.insert(title: 'Test', owner: 1));
+    });
+    await oldDb.close();
+
+    // Run the migration and verify that it adds the view.
+    final db = Database(schema.newConnection());
+    await verifier.migrateAndValidate(db, 5);
+    await db.close();
+
+    // Make sure the view works!
+    final migratedDb = v5.DatabaseAtV5.connect(schema.newConnection());
+    final viewCount = await migratedDb.select(migratedDb.groupCount).get();
+
+    expect(
+        viewCount,
+        contains(isA<v5.GroupCountData>()
+            .having((e) => e.id, 'id', 1)
+            .having((e) => e.groupCount, 'groupCount', 1)));
+    expect(
+        viewCount,
+        contains(isA<v5.GroupCountData>()
+            .having((e) => e.id, 'id', 2)
+            .having((e) => e.groupCount, 'groupCount', 0)));
+    await migratedDb.close();
+  });
 }