docs: @Override
      protected AstNode parseAlterTableStatement( DdlTokenStream tokens,
                                                  AstNode parentNode ) throws ParsingException {
          assert tokens != null;
          assert parentNode != null;
          // TODO:
          //
          /*
           * 
  
          ALTER [ONLINE | OFFLINE] [IGNORE] TABLE tbl_name
              alter_specification [, alter_specification] ...
  
              alter_specification:
                  table_options
                | ADD [COLUMN] col_name column_definition
                      [FIRST | AFTER col_name ]
                | ADD [COLUMN] (col_name column_definition,...)
                | ADD {INDEX|KEY} [index_name]
                      [index_type] (index_col_name,...) [index_option] ...
                | ADD [CONSTRAINT [symbol]] PRIMARY KEY
                      [index_type] (index_col_name,...) [index_option] ...
                | ADD [CONSTRAINT [symbol]]
                      UNIQUE [INDEX|KEY] [index_name]
                      [index_type] (index_col_name,...) [index_option] ...
                | ADD FULLTEXT [INDEX|KEY] [index_name]
                      (index_col_name,...) [index_option] ...
                | ADD SPATIAL [INDEX|KEY] [index_name]
                      (index_col_name,...) [index_option] ...
                | ADD [CONSTRAINT [symbol]]
                      FOREIGN KEY [index_name] (index_col_name,...)
                      reference_definition
                | ALTER [COLUMN] col_name {SET DEFAULT literal | DROP DEFAULT}
                | CHANGE [COLUMN] old_col_name new_col_name column_definition
                      [FIRST|AFTER col_name]
                | MODIFY [COLUMN] col_name column_definition
                      [FIRST | AFTER col_name]
                | DROP [COLUMN] col_name
                | DROP PRIMARY KEY
                | DROP {INDEX|KEY} index_name
                | DROP FOREIGN KEY fk_symbol
                | DISABLE KEYS
                | ENABLE KEYS
                | RENAME [TO] new_tbl_name
                | ORDER BY col_name [, col_name] ...
                | CONVERT TO CHARACTER SET charset_name [COLLATE collation_name]
                | [DEFAULT] CHARACTER SET [=] charset_name [COLLATE [=] collation_name]
                | DISCARD TABLESPACE
                | IMPORT TABLESPACE
                | partition_options
                | ADD PARTITION (partition_definition)
                | DROP PARTITION partition_names
                | COALESCE PARTITION number
                | REORGANIZE PARTITION [partition_names INTO (partition_definitions)]
                | ANALYZE PARTITION partition_names
                | CHECK PARTITION partition_names
                | OPTIMIZE PARTITION partition_names
                | REBUILD PARTITION partition_names
                | REPAIR PARTITION partition_names
                | REMOVE PARTITIONING
           */
  
          return super.parseAlterTableStatement(tokens, parentNode);
      }