@Override
    public FilterPredicate buildPredict(Operator op, Object constant, String columnName, TypeInfo columnType) {
      switch (op) {
      case LESS_THAN:
        return lt(floatColumn(columnName), ((Number) constant).floatValue());
      case IS_NULL:
      case EQUALS:
      case NULL_SAFE_EQUALS:
        return eq(floatColumn(columnName),
            (constant == null) ? null : ((Number) constant).floatValue());
      case LESS_THAN_EQUALS:
        return ltEq(FilterApi.floatColumn(columnName), ((Number) constant).floatValue());
      default:
        throw new RuntimeException("Unknown PredicateLeaf Operator type: " + op);
      }
    }
@param op         consists of EQUALS, NULL_SAFE_EQUALS, LESS_THAN, LESS_THAN_EQUALS, IS_NULL
@param literal
@param columnName
@param columnType
@return
ql/src/java/org/apache/hadoop/hive/ql/io/parquet/LeafFilterFactory.java