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From Yin Huai <huaiyin....@gmail.com>
Subject Re: jsonRdd and MapType
Date Fri, 07 Nov 2014 21:31:55 GMT
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 <boclair@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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