[英]How to read and write Map<String, Object> from/to parquet file in Java or Scala?
[英]How to read and write a custom class from parquet file
我正在嘗試使用DataFrame / datasets為某個類類型編寫鑲木地板讀/寫類
類架構:
class A {
long count;
List<B> listOfValues;
}
class B {
String id;
long count;
}
代碼:
String path = "some path";
List<A> entries = somerandomAentries();
JavaRDD<A> rdd = sc.parallelize(entries, 1);
DataFrame df = sqlContext.createDataFrame(rdd, A.class);
df.write().parquet(path);
DataFrame newDataDF = sqlContext.read().parquet(path);
newDataDF.show();
當我嘗試運行此命令時,將引發錯誤。 我在這里想念什么? 在創建數據幀錯誤時是否需要為整個類提供一個架構:
Caused by: scala.MatchError: B(Id=abc, count=0) (of class B)
at org.apache.spark.sql.catalyst.CatalystTypeConverters$StructConverter.toCatalystImpl(CatalystTypeConverters.scala:255)
at org.apache.spark.sql.catalyst.CatalystTypeConverters$StructConverter.toCatalystImpl(CatalystTypeConverters.scala:250)
at org.apache.spark.sql.catalyst.CatalystTypeConverters$CatalystTypeConverter.toCatalyst(CatalystTypeConverters.scala:102)
at org.apache.spark.sql.catalyst.CatalystTypeConverters$ArrayConverter.toCatalystImpl(CatalystTypeConverters.scala:169)
at org.apache.spark.sql.catalyst.CatalystTypeConverters$ArrayConverter.toCatalystImpl(CatalystTypeConverters.scala:153)
at org.apache.spark.sql.catalyst.CatalystTypeConverters$CatalystTypeConverter.toCatalyst(CatalystTypeConverters.scala:102)
at org.apache.spark.sql.catalyst.CatalystTypeConverters$$anonfun$createToCatalystConverter$2.apply(CatalystTypeConverters.scala:401)
at org.apache.spark.sql.SQLContext$$anonfun$org$apache$spark$sql$SQLContext$$beansToRows$1$$anonfun$apply$1.apply(SQLContext.scala:1358)
at org.apache.spark.sql.SQLContext$$anonfun$org$apache$spark$sql$SQLContext$$beansToRows$1$$anonfun$apply$1.apply(SQLContext.scala:1358)
at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:244)
at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:244)
at scala.collection.IndexedSeqOptimized$class.foreach(IndexedSeqOptimized.scala:33)
at scala.collection.mutable.ArrayOps$ofRef.foreach(ArrayOps.scala:108)
at scala.collection.TraversableLike$class.map(TraversableLike.scala:244)
at scala.collection.mutable.ArrayOps$ofRef.map(ArrayOps.scala:108)
at org.apache.spark.sql.SQLContext$$anonfun$org$apache$spark$sql$SQLContext$$beansToRows$1.apply(SQLContext.scala:1358)
at org.apache.spark.sql.SQLContext$$anonfun$org$apache$spark$sql$SQLContext$$beansToRows$1.apply(SQLContext.scala:1356)
at scala.collection.Iterator$$anon$11.next(Iterator.scala:328)
at org.apache.spark.sql.execution.datasources.DefaultWriterContainer.writeRows(WriterContainer.scala:263)
... 8 more
您收到錯誤消息,因為Spark 1.6版本不支持嵌套JavaBean。 請參閱https://spark.apache.org/docs/1.6.0/sql-programming-guide.html#inferring-the-schema-using-reflection
當前,Spark SQL不支持包含嵌套或包含復雜類型(例如列表或數組)的JavaBean。
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