我在hive中有一个表，其结构如下：

> describe volatility2;
Query: describe volatility2
+------------------+---------------+---------+
| name             | type          | comment |
+------------------+---------------+---------+
| version          | int           |         |
| unmappedmkfindex | int           |         |
| mfvol            | array<string> |         |
+------------------+---------------+---------+

它是由spark hivecontext代码使用如下dataframe api创建的：

val volDF = hc.createDataFrame(volRDD)
volDF.saveAsTable(volName)

它继承了模式中定义的rdd结构：

def schemaVolatility: StructType = StructType(
    StructField("Version", IntegerType, false) ::
    StructField("UnMappedMKFIndex", IntegerType, false) ::
    StructField("MFVol", DataTypes.createArrayType(StringType), true) :: Nil)

但是，当我试图使用最新的jdbc impala驱动程序从这个表中进行选择时，最后一列对它不可见。我的查询非常简单—尝试将数据打印到控制台—与驱动程序下载提供的示例代码完全相同：

String sqlStatement = "select * from default.volatility2";
Class.forName(jdbcDriverName);
con = DriverManager.getConnection(connectionUrl);
Statement stmt = con.createStatement();
ResultSet rs = stmt.executeQuery(sqlStatement);
System.out.println("\n== Begin Query Results ======================");
ResultSetMetaData metadata = rs.getMetaData();
for (int i=1; i<=metadata.getColumnCount(); i++) {
    System.out.println(rs.getMetaData().getColumnName(i)+":"+rs.getMetaData().getColumnTypeName(i));
}
System.out.println("== End Query Results =======================\n\n");

控制台输出如下：

== Begin Query Results ======================
version:version
unmappedmkfindex:unmappedmkfindex
== End Query Results =======================

是司机的错误还是我遗漏了什么？