CODEWITHSUNDEEP
jsonapache-sparkdataset
Eoin Lane
Eoin Lane

Reputation: 691

Exploding a JSON array in a Spark Dataset

I am using Spark 2.1 and Zeppelin 0.7 to do the following. (this is inspired by the Databricks tutorial (https://databricks.com/blog/2017/01/19/real-time-streaming-etl-structured-streaming-apache-spark-2-1.html))

I have created the following schema 

val jsonSchema = new StructType()
.add("Records", ArrayType(new StructType()
    .add("Id", IntegerType)
    .add("eventDt", StringType)
    .add("appId", StringType)
    .add("userId", StringType)
    .add("eventName", StringType)
    .add("eventValues", StringType)
   )
  )

to read in the following json 'array' file, which i have in my 'inputPath' directory

{
"Records": [{
    "Id": 9550,
    "eventDt": "1491810477700",
    "appId": "dandb01",
    "userId": "985580",
    "eventName": "OG: HR: SELECT",
    "eventValues": "985087"
    },
    ... other records
]}

val rawRecords = spark.read.schema(jsonSchema).json(inputPath)

I then want to explode these records to get to the individual events

val events = rawRecords.select(explode($"Records").as("record"))

But rawRecords.show() and events.show() are both null.

Any idea what i am doing wrong? In the past i know i should be using JSONL for this, but the Databricks tutorial suggests that the latest version of spark should now support json arrays.

Upvotes: 0

Views: 2587

Answers (1)

Sanchit Grover
Sanchit Grover

Reputation: 1008

I did the following :

  1. I have a file foo.txt with below data

{"Records":[{"Id":9550,"eventDt":"1491810477700","appId":"dandb01","userId":"985580","eventName":"OG:HR:SELECT","eventValues":"985087"},{"Id":9550,"eventDt":"1491810477700","appId":"dandb01","userId":"985580","eventName":"OG:HR:SELECT","eventValues":"985087"},{"Id":9550,"eventDt":"1491810477700","appId":"dandb01","userId":"985580","eventName":"OG:HR:SELECT","eventValues":"985087"},{"Id":9550,"eventDt":"1491810477700","appId":"dandb01","userId":"985580","eventName":"OG:HR:SELECT","eventValues":"985087"}]} {"Records":[{"Id":9550,"eventDt":"1491810477700","appId":"dandb01","userId":"985580","eventName":"OG:HR:SELECT","eventValues":"985087"},{"Id":9550,"eventDt":"1491810477700","appId":"dandb01","userId":"985580","eventName":"OG:HR:SELECT","eventValues":"985087"},{"Id":9550,"eventDt":"1491810477700","appId":"dandb01","userId":"985580","eventName":"OG:HR:SELECT","eventValues":"985087"},{"Id":9550,"eventDt":"1491810477700","appId":"dandb01","userId":"985580","eventName":"OG:HR:SELECT","eventValues":"985087"}]}

  1. I have the following code

    import sqlContext.implicits._ import org.apache.spark.sql.functions._

    val df = sqlContext.read.json("foo.txt") df.printSchema()
    df.select(explode($"Records").as("record")).show

  2. I get the following output

root |-- Records: array (nullable = true) | |-- element: struct (containsNull = true) | | |-- Id: long (nullable = true) |
| |-- appId: string (nullable = true) | | |-- eventDt: string (nullable = true) | | |-- eventName: string (nullable = true) | | |-- eventValues: string (nullable = true) | |
|-- userId: string (nullable = true)

+--------------------+
|              record|
+--------------------+
|[9550,dandb01,149...|
|[9550,dandb01,149...|
|[9550,dandb01,149...|
|[9550,dandb01,149...|
|[9550,dandb01,149...|
|[9550,dandb01,149...|
|[9550,dandb01,149...|
|[9550,dandb01,149...|
+--------------------+

Upvotes: 1

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