code: public function dropIndex($name, $table)
      {
          return 'DROP INDEX ' . $this->db->quoteTableName($name) . ' ON ' . $this->db->quoteTableName($table);
      }
docs: Builds a SQL statement for dropping an index.
  @param string $name the name of the index to be dropped. The name will be properly quoted by the method.
  @param string $table the table whose index is to be dropped. The name will be properly quoted by the method.
  @return string the SQL statement for dropping an index.