@Override
            public int compare(RexLiteral o1, RexLiteral o2) {
              if(o1 == o2) {
                return 0;
              } else {
                return 1;
              }
            }
Add PK-FK join information to the AST as a query hint
@param ast
@param join
@param swapSides whether the left and right input of the join is swapped
ql/src/java/org/apache/hadoop/hive/ql/optimizer/calcite/translator/ASTConverter.java