public void setInputCol(int inputCol) {
    this.inputColumnNum[0] = inputCol;
  }
Superclass to support vectorized functions that take a string
and return a long, optionally with additional configuration arguments.
Used for cast(string), length(string), etc
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/FuncStringToLong.java