private boolean checkTypeInfoForDecimal64(TypeInfo typeInfo) {
    if (typeInfo instanceof DecimalTypeInfo) {
      DecimalTypeInfo decimalTypeInfo = (DecimalTypeInfo) typeInfo;
      return HiveDecimalWritable.isPrecisionDecimal64(decimalTypeInfo.precision());
    }
    return false;
  }
Used as a fast path for operations that don't modify their input, like unary +
and casting boolean to long. IdentityExpression and its children are always
projections.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/VectorizationContext.java