anchor.diff:  
   Future<SqlResultSet> createTable(SqlTransaction transaction, String tableName,
       String columnName) {
  -  final completer = new Completer<SqlResultSet>();
  +  final completer = new Completer<SqlResultSet>.sync();
   
     final sql = 'CREATE TABLE $tableName ($columnName)';
     transaction.executeSql(sql, [],
  
positive.code: }
  
  Future<SqlResultSet> queryTable(SqlTransaction transaction, String tableName) {
    final completer = new Completer<SqlResultSet>();
  
    final sql = 'SELECT * FROM $tableName';
    transaction.executeSql(sql, [],
  
negative.code: }
  
  Future<SqlTransaction> transaction(SqlDatabase db) {
    final completer = new Completer<SqlTransaction>.sync();
  
    db.transaction((SqlTransaction transaction) {
      completer.complete(transaction);
  