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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