public String vectorExpressionParameters() {
    return getColumnParamString(0, inputColumnNum[0]);
  }
To be used to cast long and boolean to decimal.
This works for boolean too because boolean is encoded as 0
for false and 1 for true.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/CastLongToDecimal64.java