anchor.diff:     ;
   
   distinct_clause
  -   : DISTINCT
  -   | DISTINCT ON OPEN_PAREN expr_list CLOSE_PAREN
  +   : DISTINCT (ON OPEN_PAREN expr_list CLOSE_PAREN)?
      ;
   
   opt_all_clause
  
positive.code:    ;
  
  ruleactionmulti
     : ruleactionmulti SEMI ruleactionstmtOrEmpty
     | ruleactionstmtOrEmpty
     ;
  
  ruleactionstmt
  
negative.code:    ;
  
  vacuum_relation_list
     : vacuum_relation (COMMA vacuum_relation)*
     ;
  
  opt_vacuum_relation_list
  