我从Cassandra阅读数据：

df = spark.read\
    .format("org.apache.spark.sql.cassandra")\
    .options(**configs)\
    .options(table=tablename, keyspace=keyspace)\
    .option("ssl", True)\
    .option("sslmode", "require")\
    .load()

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这个df就是pyspark dataframe。我可以在这个df上执行show（），printSchema（）函数，但是当我打印时

df.count()

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抛出错误：

An error was encountered:
An error occurred while calling o1394.count.
: org.apache.spark.SparkException: Job aborted due to stage failure: Task 19 in stage 
48.0 failed 4 times, most recent failure: Lost task 19.3 in stage 48.0 (TID 2053, js- 
56258-63801-i-32-w-1.net, executor 9): java.lang.IllegalArgumentException: 
requirement failed: Column not found in Java driver Row: count

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如何解决此问题？提前致谢