anchor.diff:          //OR	left	logical disjunction
          | a_expr OR a_expr
   
  -       | a_expr LESS_LESS a_expr
  -       | a_expr GREATER_GREATER a_expr
  +       | a_expr (LESS_LESS|GREATER_GREATER) a_expr
   
          | a_expr qual_op
          | a_expr not_la? IN_P in_expr
  
positive.code: 	;
  */
  
   table_ref: relation_expr opt_alias_clause # table_ref_simple
            | relation_expr opt_alias_clause tablesample_clause # table_ref_simple
            | func_table func_alias_clause # table_ref_simple
            | LATERAL_P func_table func_alias_clause # table_ref_simple
            | xmltable opt_alias_clause # table_ref_simple
            | LATERAL_P xmltable opt_alias_clause # table_ref_simple
            | select_with_parens opt_alias_clause # table_ref_simple
            | LATERAL_P select_with_parens opt_alias_clause # table_ref_simple
  //todo: joined_table was inlined to (partially) solve left-recursion problem;
  //          | joined_table
            | table_ref CROSS JOIN table_ref # table_ref_joined_tables
            | table_ref join_type JOIN table_ref join_qual # table_ref_joined_tables
            | table_ref JOIN table_ref join_qual # table_ref_joined_tables
            | table_ref NATURAL join_type JOIN table_ref # table_ref_joined_tables
            | table_ref NATURAL JOIN table_ref # table_ref_joined_tables
            | OPEN_PAREN table_ref CLOSE_PAREN opt_alias_clause  # table_ref_simple
            | OPEN_PAREN
                  (
                          //table_ref
                            table_ref CROSS JOIN table_ref
                          | table_ref join_type JOIN table_ref join_qual
                          | table_ref JOIN table_ref join_qual
                          | table_ref NATURAL join_type JOIN table_ref
                          | table_ref NATURAL JOIN table_ref
                  )
            CLOSE_PAREN opt_alias_clause # table_ref_joined_tables
  ;
  
  
negative.code:                   | colid OPEN_PAREN tablefuncelementlist CLOSE_PAREN
                    |
  ;
   join_type: (FULL|LEFT|RIGHT|INNER_P) OUTER_P?
  ;
  
   join_qual: USING OPEN_PAREN name_list CLOSE_PAREN
            | ON a_expr
  ;
  