@Override
  public String vectorExpressionParameters() {
    return getColumnParamString(0, getMapColumnNum()) + ", key: " + key;
  }
Returns value of Map.
Extends {@link VectorUDFMapIndexBaseScalar}
ql/src/java/org/apache/hadoop/hive/ql/exec/vector/expressions/VectorUDFMapIndexLongScalar.java