Spark JDBC：DataFrameReader无法读取数据类型为ROWID的Oracle表

Question

我正在尝试使用spark.read.format读取Oracle表，它适用于所有表，除了少数表的列的数据类型为ROWID。

下面是我的代码

var df = spark.read.format("jdbc").
        option("url", url).
        option("driver", driver).
        option("dbtable", dbTable).load()
println(df.first)

我收到以下错误

18/09/08 11:38:17 WARN scheduler.TaskSetManager: Lost task 0.0 in stage 5.0 (TID 23, gbrdsr000002985.intranet.barcapint.com, executor 21): java.sql.SQLException: Invalid column type: getLong not implemented for class oracle.jdbc.driver.T4CRowidAccessor
    at oracle.jdbc.driver.GeneratedAccessor.getLong(GeneratedAccessor.java:440)
    at oracle.jdbc.driver.GeneratedStatement.getLong(GeneratedStatement.java:228)
    at oracle.jdbc.driver.GeneratedScrollableResultSet.getLong(GeneratedScrollableResultSet.java:620)
    at org.apache.spark.sql.execution.datasources.jdbc.JdbcUtils$$anonfun$org$apache$spark$sql$execution$datasources$jdbc$JdbcUtils$$makeGetter$8.apply(JdbcUtils.scala:365)
    at org.apache.spark.sql.execution.datasources.jdbc.JdbcUtils$$anonfun$org$apache$spark$sql$execution$datasources$jdbc$JdbcUtils$$makeGetter$8.apply(JdbcUtils.scala:364)

分析：我检查了JdbcUtils对象，发现java.sql.Types.ROWID的情况映射到spark的LongType。但是在Oracle JDBC驱动程序中未为ROWID类型实现getLong。我有信心，如果我设法将其映射到StringType，它将可以工作，但我找不到任何解决方法。请在此处建议解决方案。

到目前为止，我正在使用ResultSet读取数据，然后使用自定义架构将其转换为DataFrame，但是它杀死了并行性。我还想检查是否有任何修改JdbcUtils代码的选项，因为由于类定义中提到了“ private [sql]”，因此我无法扩展DataFrameReader来创建自定义代码。

Answer 1

val df=spark.read
  .format("jdbc")
  .option("driver","oracle.jdbc.OracleDriver")
  .option("url","jdbc:oracle:thin:@localhost:1521:orcl")
  .option("user","oracle1")
  .option("password","oracle1")
  .option("dbtable","(select Cast(RID as VARCHAR2(18)) from sample.ALL_RESULTS_DATA)  my_table")
  .load()

RID是Oracle中数据类型为ROWID的列名。

上面的代码会将ROWID数据类型转换为String，以便我们可以使用Spark读取它

结果：

-------------------------+
|CAST(RIDASVARCHAR2(18))AS|
+-------------------------+
|       AAAIVuAABAAAMhCAAA|
|       AAAIVuAABAAAMhCAAA|
|       AAAIVuAABAAAMhCAAA|
|       AAAIVuAABAAAMhCAAA|
|       AAAIVuAABAAAMhCAAA|
|       AAAIVuAABAAAMhCAAA|
|       AAAIVuAABAAAMhCAAA|
|       AAAIVuAABAAAMhCAAA|
|       AAAIVuAABAAAMhCAAA|
|       AAAIVuAABAAAMhCAAA|
|       AAAIVuAABAAAMhCAAA|
|       AAAIVuAABAAAMhCAAA|
|       AAAIVuAABAAAMhCAAA|
|       AAAIVuAABAAAMhCAAA|
|       AAAIVuAABAAAMhCAAA|
|       AAAIVuAABAAAMhCAAA|
|       AAAIVuAABAAAMhCAAA|
|       AAAIVuAABAAAMhCAAA|
|       AAAIVuAABAAAMhCAAA|
|       AAAIVuAABAAAMhCAAA|