@Override
  protected PrimitiveTypeInfo deriveResultExactTypeInfo() {
    if (ansiSqlArithmetic) {
      return deriveResultExactTypeInfoAnsiSql();
    }
    return deriveResultExactTypeInfoBackwardsCompat();
  }
Note that in SQL, the return type of divide is not necessarily the same
as the parameters. For example, 3 / 2 = 1.5, not 1. To follow SQL, we always
return a decimal for divide.
ql/src/java/org/apache/hadoop/hive/ql/udf/generic/GenericUDFOPDivide.java