Enable legacy alter table in alterTable

drift/CHANGELOG.md

@@ -8,6 +8,8 @@
   generate a mapping to the new `DriftAny` type.
 - Fix `UNIQUE` keys declared in drift files being written twice.
 - Fix `customConstraints` not appearing in dumped database schema files.
+- Work-around an issue causing complex migrations via `Migrator.alterTable` not to
+  work if a view referenced the altered table.
 
 ## 2.3.0-dev
 

drift/lib/src/runtime/query_builder/migration.dart

@@ -146,6 +146,9 @@ class Migrator {
     final foreignKeysEnabled =
         (await _db.customSelect('PRAGMA foreign_keys').getSingle())
             .read<bool>('foreign_keys');
+    final legacyAlterTable =
+        (await _db.customSelect('PRAGMA legacy_alter_table').getSingle())
+            .read<bool>('legacy_alter_table');
 
     if (foreignKeysEnabled) {
       await _db.customStatement('PRAGMA foreign_keys = OFF;');
@@ -235,11 +238,24 @@ class Migrator {
       // Step 6: Drop the old table
       await _issueCustomQuery('DROP TABLE ${context.identifier(tableName)}');
 
+      // This step is not mentioned in the documentation, but: If we use `ALTER`
+      // on an inconsistent schema (and it is inconsistent right now because
+      // we've just dropped the original table), we need to enable the legacy
+      // option which skips the integrity check.
+      // See also: https://sqlite.org/forum/forumpost/0e2390093fbb8fd6
+      if (!legacyAlterTable) {
+        await _issueCustomQuery('pragma legacy_alter_table = 1;');
+      }
+
       // Step 7: Rename the new table to the old name
       await _issueCustomQuery(
           'ALTER TABLE ${context.identifier(temporaryName)} '
           'RENAME TO ${context.identifier(tableName)}');
 
+      if (!legacyAlterTable) {
+        await _issueCustomQuery('pragma legacy_alter_table = 0;');
+      }
+
       // Step 8: Re-create associated indexes, triggers and views
       for (final stmt in createAffected) {
         await _issueCustomQuery(stmt);

drift/test/integration_tests/migrations_integration_test.dart

@@ -15,7 +15,8 @@ void main() {
   test('change column types', () async {
     // Create todos table with category as text (it's an int? in Dart).
     final executor = NativeDatabase.memory(setup: (db) {
-      db.execute('''
+      db
+        ..execute('''
         CREATE TABLE todos (
           id INTEGER NOT NULL PRIMARY KEY AUTOINCREMENT,
           title TEXT NOT NULL,
@@ -25,14 +26,12 @@ void main() {
           status TEXT NULL,
           UNIQUE(title, category)
         );
-      ''');
-
-      db.execute('CREATE INDEX my_index ON todos (content);');
-
-      db.execute('INSERT INTO todos (title, content, target_date, category) '
-          "VALUES ('title', 'content', 0, '12')");
-
-      db.execute('PRAGMA foreign_keys = ON');
+      ''')
+        ..execute('CREATE INDEX my_index ON todos (content);')
+        ..execute('INSERT INTO todos (title, content, target_date, category) '
+            "VALUES ('title', 'content', 0, '12')")
+        ..execute('CREATE VIEW todo_categories AS SELECT category FROM todos;')
+        ..execute('PRAGMA foreign_keys = ON');
     });
 
     final db = TodoDb(executor);
@@ -63,6 +62,11 @@ void main() {
     final foreignKeysResult =
         await db.customSelect('PRAGMA foreign_keys').getSingle();
     expect(foreignKeysResult.read<bool>('foreign_keys'), isTrue);
+
+    // Similarly, the legacy_alter_table behavior should be disabled.
+    final legacyAlterTable =
+        await db.customSelect('PRAGMA legacy_alter_table').getSingle();
+    expect(legacyAlterTable.read<bool>('legacy_alter_table'), isFalse);
   });
 
   test('rename columns', () async {

examples/migrations_example/lib/database.dart

@@ -63,18 +63,11 @@ class Database extends _$Database {
               break;
             case 8:
               // Added a unique key to the users table
-
-              // TODO: Figure out why dropping the view is necessary (https://sqlite.org/forum/forumpost/de614349cb)
-              await m.drop(groupCount);
               await m.alterTable(TableMigration(v8.Users(this)));
-              await m.recreateAllViews();
               break;
             case 9:
               // Added a check to the users table
-              await m.drop(groupCount);
               await m.alterTable(TableMigration(users));
-              await m.recreateAllViews();
-
               break;
           }
         }