[英]Spark Structured Streaming Databricks Event Hub Schema Defining issue
現在,我正在嘗試在streamread上執行相同的架構。
val jsonSchema = StructType([ StructField("associatedEntities", struct<driver:StringType,truck:StringType>, True),
StructField("heading", StringType, True),
StructField("location", struct<accuracyType:StringType,captureDateTime:StringType,cityStateCode:StringType,description:StringType,latitude:DoubleType,longitude:DoubleType,quality:StringType,transmitDateTime:StringType>, True),
StructField("measurements", array<struct<type:StringType,uom:StringType,value:StringType>>, True),
StructField("source", struct<entityType:StringType,key:StringType,vendor:StringType>, True),
StructField("speed", DoubleType, True)])
val df = spark
.readStream
.format("eventhubs")
//.schema(jsonSchema)
.options(ehConf.toMap)
.load()
當我在筆記本中運行此單元格時“:15:錯誤:簡單表達式的非法開頭val jsonSchema = StructType([StructField(“ associatedEntities”,struct,True),”
編輯:目標是將數據放入數據框。 我可以從事件中心消息的正文中獲取json字符串,但是如果我無法使模式正常工作,我不確定從那里可以做什么。
您由於架構定義而收到錯誤消息。 模式定義應如下所示:
import org.apache.spark.sql.types._
val jsonSchema = StructType(
Seq(StructField("associatedEntities",
StructType(Seq(
StructField("driver", StringType),
StructField ("truck", StringType)
))),
StructField("heading", StringType),
StructField("measurements", ArrayType(StructType(Seq(StructField ("type", StringType), StructField ("uom", StringType), StructField("value", StringType)))))
)
)
您可以使用以下方法仔細檢查架構:
jsonSchema.printTreeString
返回架構:
root
|-- associatedEntities: struct (nullable = true)
| |-- driver: string (nullable = true)
| |-- truck: string (nullable = true)
|-- heading: string (nullable = true)
|-- measurements: array (nullable = true)
| |-- element: struct (containsNull = true)
| | |-- type: string (nullable = true)
| | |-- uom: string (nullable = true)
| | |-- value: string (nullable = true)
如注釋中所述,您將獲得二進制數據。 因此,首先獲得原始數據幀:
val rawData = spark.readStream
.format("eventhubs")
.option(...)
.load()
你必須:
用解析的數據定義數據框:
val parsedData = rawData
.selectExpr("cast (Body as string) as json")
.select(from_json($"json", jsonSchema).as("data"))
.select("data.*")
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