Hello Brian,
Right now, MapType is not supported in the StructType provided to
jsonRDD/jsonFile. We will add the support. I have created
https://issues.apache.org/jira/browse/SPARK-4302 to track this issue.
Thanks,
Yin
On Fri, Nov 7, 2014 at 3:41 PM, boclair bocl...@gmail.com wrote:
I'm loading json into spark to create a schemaRDD (sqlContext.jsonRDD(..)).
I'd like some of the json fields to be in a MapType rather than a sub
StructType, as the keys will be very sparse.
For example:
val sqlContext = new org.apache.spark.sql.SQLContext(sc)
import sqlContext.createSchemaRDD
val jsonRdd = sc.parallelize(Seq({key: 1234, attributes:
{gender: m}},
{key: 4321,
attributes: {location: nyc}}))
val schemaRdd = sqlContext.jsonRDD(jsonRdd)
schemaRdd.printSchema
root
|-- attributes: struct (nullable = true)
||-- gender: string (nullable = true)
||-- location: string (nullable = true)
|-- key: string (nullable = true)
schemaRdd.collect
res1: Array[org.apache.spark.sql.Row] = Array([[m,null],1234],
[[null,nyc],4321])
However this isn't what I want. So I created my own StructType to pass to
the jsonRDD call:
import org.apache.spark.sql._
val st = StructType(Seq(StructField(key, StringType, false),
StructField(attributes,
MapType(StringType, StringType, false
val jsonRddSt = sc.parallelize(Seq({key: 1234, attributes:
{gender: m}},
{key: 4321,
attributes: {location: nyc}}))
val schemaRddSt = sqlContext.jsonRDD(jsonRddSt, st)
schemaRddSt.printSchema
root
|-- key: string (nullable = false)
|-- attributes: map (nullable = true)
||-- key: string
||-- value: string (valueContainsNull = false)
schemaRddSt.collect
*** Failure ***
scala.MatchError: MapType(StringType,StringType,false) (of class
org.apache.spark.sql.catalyst.types.MapType)
at
org.apache.spark.sql.json.JsonRDD$.enforceCorrectType(JsonRDD.scala:397)
...
The schema of the schemaRDD is correct. But it seems that the json cannot
be coerced to a MapType. I can see at the line in the stack trace that
there is no case statement for MapType. Is there something I'm missing?
Is
this a bug or decision to not support MapType with json?
Thanks,
Brian
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