@Override
  public String vectorExpressionParameters() {
    return "structExpressions " + Arrays.toString(structExpressions) +
        ", fieldVectorColumnTypes " + Arrays.toString(fieldVectorColumnTypes) +
        ", structColumnMap " + Arrays.toString(structColumnMap);
  }
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