I have a huge JSON file, a small part from it as follows:
{
"socialNews": [{
"adminTagIds": "",
"fileIds": "",
"departmentTagIds": "",
........
........
"comments": [{
"commentId": "",
"newsId": "",
"entityId": "",
....
....
}]
}]
.....
}
I have applied lateral view explode on socialNews as follows:
val rdd = sqlContext.jsonFile("file:///home/ashish/test")
rdd.registerTempTable("social")
val result = sqlContext.sql("select * from social LATERAL VIEW explode(socialNews) social AS comment")
Now I want to convert back this result (DataFrame) to JSON and save into a file, but I am not able to find any Scala API to do the conversion.
Is there any standard library to do this or some way to figure it out?
val result: DataFrame = sqlContext.read.json(path)
result.write.json("/yourPath")
The method write is in the class DataFrameWriter and should be accessible to you on DataFrame objects. Just make sure that your rdd is of type DataFrame and not of deprecated type SchemaRdd. You can explicitly provide type definition val data: DataFrame or cast to dataFrame with toDF().
If you have a DataFrame there is an API to convert back to an RDD[String] that contains the json records.
val df = Seq((2012, 8, "Batman", 9.8), (2012, 8, "Hero", 8.7), (2012, 7, "Robot", 5.5), (2011, 7, "Git", 2.0)).toDF("year", "month", "title", "rating")
df.toJSON.saveAsTextFile("/tmp/jsonRecords")
df.toJSON.take(2).foreach(println)
This should be available from Spark 1.4 onward. Call the API on the result DataFrame you created.
The APIs available are listed here
sqlContext.read().json(dataFrame.toJSON())
When you run your spark job as
--master local --deploy-mode client
Then,
df.write.json('path/to/file/data.json') works.
If you run on cluster [on header node], [--master yarn --deploy-mode cluster] better approach is to write data to aws s3 or azure blob and read from it.
df.write.json('s3://bucket/path/to/file/data.json') works.
If you still can't figure out a way to convert Dataframe into JSON, you can use to_json or toJSON inbuilt Spark functions.
Let me know if you have a sample Dataframe and a format of JSON to convert.
Related
I have a Mongo change stream (a pymongo application) that is continuously getting the changes in collections. These change documents as received by the program are sent to Azure Event Hubs. A Spark notebook has to read the documents as they get into Event Hub and do Schema matching (match the fields in the document with spark table columns) with the spark table for that collection. If there are fewer fields in the document than in the table, columns have to be added with Null.
I am reading the events from Event Hub like below.
spark.readStream.format("eventhubs").option(**config).load().
As said in the documentation, the original message is in the 'body' column of the dataframe that I am converting to string. Now I have got the Mongo document as a JSON string in a streaming dataframe. I am facing below issues.
I need to extract the individual fields in the mongo document. This is needed to compare what fields are present in the spark table and what is not in Mongo document. I saw a function called get_json_object(col,path). This essentially returns a string again and I cannot individually select all the columns.
If from_json can be used to convert the JSON string to Struct type, I cannot specify the Schema because we have close to 70 collections (corresponding number of spark tables as well) each sending Mongo docs with fields from 10 to 450.
If I can convert the JSON string in streaming dataframe to a JSON object whose schema can be inferred by the dataframe (something like how read.json can do), I can use SQL * representation to extract the individual columns, do few manipulations & then save the final dataframe to the spark table. Is it possible to do that? What is the mistake I am making?
Note: Stram DF doesn't support collect() method to individually extract the JSON string from underlying rdd and do the necessary column comparisons. Using Spark 2.4 & Python in Azure Databricks environment 4.3.
Below is the sample data I get in my notebook after reading the events from event hub and casting it to string.
{
"documentKey": "5ab2cbd747f8b2e33e1f5527",
"collection": "configurations",
"operationType": "replace",
"fullDocument": {
"_id": "5ab2cbd747f8b2e33e1f5527",
"app": "7NOW",
"type": "global",
"version": "1.0",
"country": "US",
"created_date": "2018-02-14T18:34:13.376Z",
"created_by": "Vikram SSS",
"last_modified_date": "2018-07-01T04:00:00.000Z",
"last_modified_by": "Vikram Ganta",
"last_modified_comments": "Added new property in show_banners feature",
"is_active": true,
"configurations": [
{
"feature": "tip",
"properties": [
{
"id": "tip_mode",
"name": "Delivery Tip Mode",
"description": "Tip mode switches the display of tip options between percentage and amount in the customer app",
"options": [
"amount",
"percentage"
],
"default_value": "tip_percentage",
"current_value": "tip_percentage",
"mode": "multiple or single"
},
{
"id": "tip_amount",
"name": "Tip Amounts",
"description": "List of possible tip amount values",
"default_value": 0,
"options": [
{
"display": "No Tip",
"value": 0
}
]
}
]
}
]
}
}
I would like to separate and take out the full_document in the sample above. When I use get_json_object, I am getting the full_document in another streaming dataframe as JSON string and not as an object. As you can see, there are some array types in full_document which I can explode (documentation says that explode is supported in streaming DF, but havent tried) but there are some objects also (like struct type) which I would like to extract the individual fields. I cannot use the SQL '*' notation because what get_json_object returns is a string and not the object itself.
Its convincing that this much varied Schema of the JSON would be better with schema mentioned explicitly. So I took it like, in a streaming environment with very different Schema of the incoming stream, its always better to specify the schema. So I am proceeding with get_json_object and from_json and reading the schema through a file.
I am trying to parse json with this library https://github.com/momodi/Json4Scala
I have JSON that looks like this:
{
current: {pageviews: 5, time: 50, id: 'jafh784'},
allTime: {pageviews: 20, time: 438, id: 'adsf6447'}
}
val json = Json.parse(x.getString("user"))
json.asMap("current").asMap("pageviews").asInt
It is not working and I have tried several combinations of the above. I tried to use some other libraries but they were even less clear to me. The schema of the json varies but the page views is always in the same location. I am open for suggestions of another library.
Edit: I read about using case classes for nested objects but the schema is not exact across all my json. Can I just use a case class and only declare a minimum of keys?
Play Json allows you to do it without having to specify models:
import play.api.libs.json._
val raw = """{
"current": {"pageviews": 5, "time": 50, "id": "jafh784"},
"allTime": {"pageviews": 20, "time": 438, "id": "adsf6447"}
}"""
val json = Json.parse(raw).as[JsObject]
val currentPageviews = (json \ "current" \ "pageviews").as[Int]
println(currentPageviews) // 5
Here here is a link to a live example.
To include the PlayJson dependency add this to your build sbt:
libraryDependencies += "com.typesafe.play" % "play-json_2.11" % "2.6.2"
(There are also build for 2.12)
I have the following JSON file.
{
"reviewerID": "ABC1234",
"productID": "ABCDEF",
"reviewText": "GOOD!",
"rating": 5.0,
},
{
"reviewerID": "ABC5678",
"productID": "GFMKDS",
"reviewText": "Not bad!",
"rating": 3.0,
}
I want to parse without SparkSQL and use a JSON parser.
The result of parse that i want is textfile.
ABC1234::ABCDEF::5.0
ABC5678::GFMKDS::3.0
How to parse the json file by using json parser in spark scala?
tl;dr Spark SQL supports JSONs in the format of one JSON per file or per line. If you'd like to parse multi-line JSONs that can appear together in a single file, you'd have to write your own Spark support as it's not currently possible.
A possible solution is to ask the "writer" (the process that writes the files to be nicer and save one JSON per file) that would make your life much sweeter.
If that does not give you much, you'd have to use mapPartitions transformation with your parser and somehow do the parsing yourself.
val input: RDD[String] = // ... load your JSONs here
val jsons = jsonRDD.mapPartitions(json => // ... use your JSON parser here)
My requirement is to pass dataframe as input parameter to a scala class which saves the data in json format to hdfs.
The input parameter looks like this:
case class ReportA(
parm1: String,
parm2: String,
parm3: Double,
parm4: Double,
parm5: DataFrame
)
I have created a JSON object for this parameter like:
def write(xx: ReportA) = JsObject(
"field1" -> JsString(xx.parm1),
"field2" -> JsString(xx.parm2),
"field3" -> JsNumber(xx.parm3),
"field4" -> JsNumber(xx.parm4),
"field5" -> JsArray(xx.parm5)
)
parm5 is a dataframe and wanted to convert as Json array.
How can I convert the dataframe to Json array?
Thank you for your help!!!
A DataFrame can be seen to be the equivalent of a plain-old table in a database, with rows and columns. You can't just get a simple array from it, the closest you woud come to an array would be with the following structure :
[
"col1": [val1, val2, ..],
"col2": [val3, val4, ..],
"col3": [val5, val6, ..]
]
To achieve a similar structure, you could use the toJSON method of the DataFrame API to get an RDD<String> and then do collect on it (be careful of any OutOfMemory exceptions).
You now have an Array[String], which you can simply transform in a JsonArray depending on the JSON library you are using.
Beware though, this seems like a really bizarre way to use Spark, you generally don't output and transform an RDD or a DataFrame directly into one of your objects, you usually spill it out onto a storage solution.
I am looking for a way to load multiline JSON into Spark using Java. The Spark SQLContext has methods to load JSON, but it only supports "one record per line". I have a multiline JSON file that I need to process.
Example input:
The JSON contains words, definitions and example sentences :
{
"one-armedbandit":
[
{
"function": "noun",
"definition": "slot machine",
"examples":
[
]
}
],
...
}
The Spark ingestion methods indeed accept a json-line format. You could consider using a json processor to convert your data to this format before processing.
What I did was read the JSON into a List of POJOs with a JSON processor, then called parallelize on the SparkContext to get a JavaRDD.