如何有效地将多个 json 文件读入 Dataframe 或 JavaRDD？

Question

I can use the following code to read a single json file but I need to read multiple json files and merge them into one Dataframe. How can I do this?

DataFrame jsondf = sqlContext.read().json("/home/spark/articles/article.json");

Or is there a way to read multiple json files into JavaRDD then convert to Dataframe?

Answer 1

To read multiple inputs in Spark, use wildcards. That's going to be true whether you're constructing a dataframe or an rdd.

context.read().json("/home/spark/articles/*.json")
// or getting json out of s3
context.read().json("s3n://bucket/articles/201510*/*.json")

Answer 2

You can use exactly the same code to read multiple JSON files. Just pass a path-to-a-directory / path-with-wildcards instead of path to a single file.

DataFrameReader also provides json method with a following signature :

json(jsonRDD: JavaRDD[String])

which can be used to parse JSON already loaded into JavaRDD .

Answer 3

function spark.read.json accepts list of file as a parameter.

spark.read.json(List_all_json file)

This will read all the files in the list and return a single data frame for all the information in the files.

Answer 4

Function json(String... paths) takes variable arguments. ( documentation )

So you can change your code like this:

sqlContext.read().json(file1, file2, ...)

Answer 5

Using pyspark, if you have all the json files in the same folder, you can use df = spark.read.json('folder_path') . This instruction will load all the json files inside the folder.

For reading performance, I recommend you for providing dataframe the schema:

import pyspark.sql.types as T

billing_schema = billing_schema = T.StructType([
  T.StructField('accountId', T.LongType(),True),
  T.StructField('accountName',T.StringType(),True),
  T.StructField('accountOwnerEmail',T.StringType(),True),
  T.StructField('additionalInfo',T.StringType(),True),
  T.StructField('chargesBilledSeparately',T.BooleanType(),True),
  T.StructField('consumedQuantity',T.DoubleType(),True),
  T.StructField('consumedService',T.StringType(),True),
  T.StructField('consumedServiceId',T.LongType(),True),
  T.StructField('cost',T.DoubleType(),True),
  T.StructField('costCenter',T.StringType(),True),
  T.StructField('date',T.StringType(),True),
  T.StructField('departmentId',T.LongType(),True),
  T.StructField('departmentName',T.StringType(),True),
  T.StructField('instanceId',T.StringType(),True),
  T.StructField('location',T.StringType(),True),
  T.StructField('meterCategory',T.StringType(),True),
  T.StructField('meterId',T.StringType(),True),
  T.StructField('meterName',T.StringType(),True),
  T.StructField('meterRegion',T.StringType(),True),
  T.StructField('meterSubCategory',T.StringType(),True),
  T.StructField('offerId',T.StringType(),True),
  T.StructField('partNumber',T.StringType(),True),
  T.StructField('product',T.StringType(),True),
  T.StructField('productId',T.LongType(),True),
  T.StructField('resourceGroup',T.StringType(),True),
  T.StructField('resourceGuid',T.StringType(),True),
  T.StructField('resourceLocation',T.StringType(),True),
  T.StructField('resourceLocationId',T.LongType(),True),
  T.StructField('resourceRate',T.DoubleType(),True),
  T.StructField('serviceAdministratorId',T.StringType(),True),
  T.StructField('serviceInfo1',T.StringType(),True),
  T.StructField('serviceInfo2',T.StringType(),True),
  T.StructField('serviceName',T.StringType(),True),
  T.StructField('serviceTier',T.StringType(),True),
  T.StructField('storeServiceIdentifier',T.StringType(),True),
  T.StructField('subscriptionGuid',T.StringType(),True),
  T.StructField('subscriptionId',T.LongType(),True),
  T.StructField('subscriptionName',T.StringType(),True),
  T.StructField('tags',T.StringType(),True),
  T.StructField('unitOfMeasure',T.StringType(),True)
])

billing_df = spark.read.json('/mnt/billingsources/raw-files/202106/', schema=billing_schema)