@Override
  public void setStructColumnExprs(VectorizationContext vContext,
      List<ExprNodeDesc> structColumnExprs, ColumnVector.Type[] fieldVectorColumnTypes)
          throws HiveException {

    structExpressions = vContext.getVectorExpressions(structColumnExprs);
    structColumnMap = new int[structExpressions.length];
    for (int i = 0; i < structColumnMap.length; i++) {
      VectorExpression ve = structExpressions[i];
      structColumnMap[i] = ve.getOutputColumnNum();
    }
    this.fieldVectorColumnTypes = fieldVectorColumnTypes;
  }
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