@Override
  public void setScratchBytesColumn(int scratchBytesColumn) {

    // Tell our super class FilterStringColumnInList it will be evaluating our scratch
    // BytesColumnVector.
    super.setInputColumn(scratchBytesColumn);
    this.scratchBytesColumn = scratchBytesColumn;
  }
After construction you must call setInListValues() to add the values to the IN set
(on the IStringInExpr interface).
<p>
And, call a and b on the IStructInExpr interface.
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/FilterStructColumnInList.java