code: public static function statement(Database $database, $modelName, $tableName, array $tableDefinition, $indexName)
      {
          $indexDefinition = $tableDefinition['indexes'][$indexName];
          $indexes = array();
          foreach ($indexDefinition as $field) {
              if (isset($tableDefinition['fields'][$field]['name']) === true) {
                  $indexes[] = $tableDefinition['fields'][$field]['name'];
              } else {
                  $indexes[] = Helper::codifyName($modelName) . '_' . Helper::codifyName($field);
              }
          }
          $statement = $database->getMasterLink()->prepare('CREATE INDEX idx_' . $indexName . ' ON ' . $tableName . ' (' . implode(', ', $indexes) . ')');
  
          return $statement;
      }
docs: Prepare and return according PDO statement.
  
  @param  Database     $database        database
  @param  string       $modelName       model name
  @param  string       $tableName       table real name
  @param  array        $tableDefinition table definition
  @param  string       $indexName       index name
  @return \PDOStatement $statement prepared query