Schema

Schema features are separated from query execution:

• Query execution lives on DriverAdapter
• Schema operations / introspection live on SchemaDriver
• Schema dump/load is optional via SchemaStateProvider

SchemaDriver

Drivers that support migrations and schema operations implement SchemaDriver. It supports:

• applying schema plans (applySchemaPlan)
• previewing schema plans (describeSchemaPlan)
• introspecting live metadata (tables, columns, indexes, foreign keys)

Ormed’s migration runner builds schema plans from migrations (a list of mutations), and then asks the active driver to apply them.

SchemaInspector

SchemaInspector is a small helper around SchemaDriver for common checks:

Future<bool> hasUsersTable(DataSource dataSource) async {
  final driver = dataSource.connection.driver;
  if (driver is! SchemaDriver) return false;
  final inspector = SchemaInspector(driver);
  return inspector.hasTable('users');
}

Schema plan previews

For schema work, the plan type is SchemaPlan (a list of SchemaMutation entries). Drivers can preview a plan without running it:

SchemaPreview previewSchemaPlan(DataSource dataSource) {
  final driver = dataSource.connection.driver;
  if (driver is! SchemaDriver) {
    throw StateError('Driver does not support schema operations.');
  }
  final plan = SchemaPlan(
    mutations: [
      SchemaMutation.rawSql(
        'CREATE TABLE IF NOT EXISTS test_table (id INTEGER PRIMARY KEY)',
      ),
    ],
    description: 'demo plan preview',
  );
  return driver.describeSchemaPlan(plan);
}

Use previews when you want to:

• show “what would run” without applying changes
• log/inspect generated DDL in tests
• build migration tooling that explains a plan

Schema dumps (SchemaStateProvider)

Some features (like schema dumps used for migration squashing) rely on an optional interface:

• SchemaStateProvider.createSchemaState(...) returns a SchemaState?
• SchemaState can dump(...) and load(...) when supported

Future<void> dumpSchemaIfSupported(DataSource dataSource) async {
  final driver = dataSource.connection.driver;
  if (driver is! SchemaStateProvider) return;
  final state = driver.createSchemaState(
    connection: dataSource.connection,
    ledgerTable: 'orm_migrations',
  );
  if (state == null || !state.canDump) return;
  await state.dump(File('database/schema.sql'));
}