protected String getColumnParamString(int typeNum, int columnNum) {
    return "col " + columnNum + ":" + getParamTypeString(typeNum);
  }
Evaluate the child expressions on the given input batch.
@param vrg {@link VectorizedRowBatch}
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/VectorExpression.java