Details
Minor Description
If the optional metadata passed to `pyspark.sql.types.StructField` includes a pythonic `None`, the `pyspark.SparkContext.createDataFrame` will fail with a very cryptic/unhelpful error.
Here is a minimal reproducible example:
# Assumes sc exists
import pyspark.sql.types as types
sqlContext = SQLContext(sc)
literal_metadata = types.StructType([
types.StructField(
'name',
types.StringType(),
nullable=True,
metadata={'comment': 'From accounting system.'}
),
types.StructField(
'age',
types.IntegerType(),
nullable=True,
metadata={'comment': None}
),
])
literal_rdd = sc.parallelize([
['Bob', 34],
['Dan', 42],
])
print(literal_rdd.take(2))
failed_dataframe = sqlContext.createDataFrame(
literal_rdd,
literal_metadata,
)
This produces the following ~stacktrace:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<string>", line 28, in <module>
File "S:\ZQL\Software\Hotware\spark-1.5.0-bin-hadoop2.6\python\pyspark\sql\context.py", line 408, in createDataFrame
jdf = self._ssql_ctx.applySchemaToPythonRDD(jrdd.rdd(), schema.json())
File "S:\ZQL\Software\Hotware\spark-1.5.0-bin-hadoop2.6\python\lib\py4j-0.8.2.1-src.zip\py4j\java_gateway.py", line 538, in __call__
File "S:\ZQL\Software\Hotware\spark-1.5.0-bin-hadoop2.6\python\pyspark\sql\utils.py", line 36, in deco
return f(*a, **kw)
File "S:\ZQL\Software\Hotware\spark-1.5.0-bin-hadoop2.6\python\lib\py4j-0.8.2.1-src.zip\py4j\protocol.py", line 300, in get_return_value
py4j.protocol.Py4JJavaError: An error occurred while calling o757.applySchemaToPythonRDD.
: java.lang.RuntimeException: Do not support type class scala.Tuple2.
at org.apache.spark.sql.types.Metadata$$anonfun$fromJObject$1.apply(Metadata.scala:160)
at org.apache.spark.sql.types.Metadata$$anonfun$fromJObject$1.apply(Metadata.scala:127)
at scala.collection.immutable.List.foreach(List.scala:318)
at org.apache.spark.sql.types.Metadata$.fromJObject(Metadata.scala:127)
at org.apache.spark.sql.types.DataType$.org$apache$spark$sql$types$DataType$$parseStructField(DataType.scala:173)
at org.apache.spark.sql.types.DataType$$anonfun$parseDataType$1.apply(DataType.scala:148)
at org.apache.spark.sql.types.DataType$$anonfun$parseDataType$1.apply(DataType.scala:148)
at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:244)
at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:244)
at scala.collection.immutable.List.foreach(List.scala:318)
at scala.collection.TraversableLike$class.map(TraversableLike.scala:244)
at scala.collection.AbstractTraversable.map(Traversable.scala:105)
at org.apache.spark.sql.types.DataType$.parseDataType(DataType.scala:148)
at org.apache.spark.sql.types.DataType$.fromJson(DataType.scala:96)
at org.apache.spark.sql.SQLContext.parseDataType(SQLContext.scala:961)
at org.apache.spark.sql.SQLContext.applySchemaToPythonRDD(SQLContext.scala:970)
at sun.reflect.GeneratedMethodAccessor38.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at py4j.reflection.MethodInvoker.invoke(MethodInvoker.java:231)
at py4j.reflection.ReflectionEngine.invoke(ReflectionEngine.java:379)
at py4j.Gateway.invoke(Gateway.java:259)
at py4j.commands.AbstractCommand.invokeMethod(AbstractCommand.java:133)
at py4j.commands.CallCommand.execute(CallCommand.java:79)
at py4j.GatewayConnection.run(GatewayConnection.java:207)
at java.lang.Thread.run(Unknown Source)
I believe the most important line of the traceback is this one:
py4j.protocol.Py4JJavaError: An error occurred while calling o757.applySchemaToPythonRDD. : java.lang.RuntimeException: Do not support type class scala.Tuple2.
But it wasn't enough for me to figure out the problem; I had to steadily simplify my program until I could identify what caused the problem.
