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dataframe - 遍历 Dataset 中具有键值对数组的列，并找出具有最大值的对

问题描述

我在数据框中有数据，该数据是从 azure eventthub 获得的。然后我将此数据转换为 json 对象并将所需的数据存储到数据集中，如下所示。

从 eventthub 获取数据并将其存储到数据框中的代码。

val connectionString = ConnectionStringBuilder(<ENDPOINT URL>)
    .setEventHubName(<EVENTHUB NAME>).build

val currTime = Instant.now
val ehConf = EventHubsConf(connectionString)
    .setConsumerGroup("<CONSUMER GRP>")
    .setStartingPosition(EventPosition
             .fromEnqueuedTime(currTime.minus(Duration.ofMinutes(30))))
    .setEndingPosition(EventPosition.fromEnqueuedTime(currTime))

val reader =  spark.read.format("eventhubs").options(ehConf.toMap).load()

var SIGNALS =  reader
    .select(get_json_object(($"body").cast("string"),"$.NUM").alias("NUM"),
            get_json_object(($"body").cast("string"),"$.SIG1").alias("SIG1"),
            get_json_object(($"body").cast("string"),"$.SIG2").alias("SIG2"),
            get_json_object(($"body").cast("string"),"$.SIG3").alias("SIG3"),
            get_json_object(($"body").cast("string"),"$.SIG4").alias("SIG4")
     )

val SIGNALSFiltered = SIGNALS.filter(col("SIG1").isNotNull &&
    col("SIG2").isNotNull && col("SIG3").isNotNull && col("SIG4").isNotNull)

在SIGNALSFiltered获得的数据如下所示。

+-----------------+--------------------+--------------------+--------------------+--------------------+
|              NUM|                SIG1|                SIG2|                SIG3|                SIG4|
+-----------------+--------------------+--------------------+--------------------+--------------------+
|XXXXX01|[{"TIME":15695605310...|[{"TIME":15695605310...|[{"TIME":15695605310...|[{"TIME":15695605310...|
|XXXXX02|[{"TIME":15695604780...|[{"TIME":15695604780...|[{"TIME":15695604780...|[{"TIME":15695604780...|
|XXXXX03|[{"TIME":15695605310...|[{"TIME":15695605310...|[{"TIME":15695605310...|[{"TIME":15695605310...|
|XXXXX04|[{"TIME":15695605310...|[{"TIME":15695605310...|[{"TIME":15695605310...|[{"TIME":15695605310...|
|XXXXX05|[{"TIME":15695605310...|[{"TIME":15695605310...|[{"TIME":15695605310...|[{"TIME":15695605310...|
|XXXXX06|[{"TIME":15695605340...|[{"TIME":15695605340...|[{"TIME":15695605340...|[{"TIME":15695605340...|
|XXXXX07|[{"TIME":15695605310...|[{"TIME":15695605310...|[{"TIME":15695605310...|[{"TIME":15695605310...|
|XXXXX08|[{"TIME":15695605310...|[{"TIME":15695605310...|[{"TIME":15695605310...|[{"TIME":15695605310...|

如果我们检查单个行的整个数据，它将如下所示。

|XXXXX01|[{"TIME":1569560531000,"VALUE":3.7825},{"TIME":1569560475000,"VALUE":3.7812},{"TIME":1569560483000,"VALUE":3.7812},{"TIME":1569560491000,"VALUE":34.7875}]|
    [{"TIME":1569560537000,"VALUE":3.7825},{"TIME":1569560481000,"VALUE":34.7825},{"TIME":1569560489000,"VALUE":34.7825},{"TIME":1569560497000,"VALUE":34.7825}]|
    [{"TIME":1569560505000,"VALUE":34.7825},{"TIME":1569560513000,"VALUE":34.7825},{"TIME":1569560521000,"VALUE":34.7825},{"TIME":1569560527000,"VALUE":34.7825}]|
    [{"TIME":1569560535000,"VALUE":34.7825},{"TIME":1569560479000,"VALUE":34.7825},{"TIME":1569560487000,"VALUE":34.7825}]

我只想要每列中最高的 TIME 对，而不是整个 TIME VALUE 对。输出应如下所示。

+-----------------+-----------------------------+---------------------------------------+---------------------------------------+----------------------------------------+
|              NUM|                         SIG1|                                   SIG2|                                   SIG3|                                    SIG4|
+-----------------+-----------------------------+---------------------------------------+---------------------------------------+----------------------------------------+
|XXXXX01|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":4.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":5.7825}]|
|XXXXX02|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":6.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":7.7825}]|
|XXXXX03|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":9.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":8.7825}]|
  1. 如何遍历每一行中的每一列并获得最高的 TIME-VALUE 对？

  2. 在每列（SIG1，....SIG4）中获得最高之后，只需更新其中最高的所有列中的 TIME 值。

  3. 有没有办法将基础数据集转换如下？列中的每个元素都应转换为新行。

+-----------------+-----------------------------+---------------------------------------+---------------------------------------+----------------------------------------+
|    NUM|                                   SIG1|                                   SIG2|                                   SIG3|                                    SIG4|
+-----------------+-----------------------------+---------------------------------------+---------------------------------------+----------------------------------------+
|XXXXX01|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|
|XXXXX01|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|
|XXXXX01|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|        null                           |[{"TIME":1569560531000,"VALUE":3.7825}]|
|XXXXX01|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|
|XXXXX02|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|
|XXXXX02|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|
|XXXXX02|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|
|XXXXX02|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|[{"TIME":1569560531000,"VALUE":3.7825}]|```

Any leads or help is appreciated! Thanks in Advance.

标签： dataframeapache-sparkapache-spark-sqlapache-spark-dataset

解决方案

您必须编写一个用户定义的函数，如下所示。这将循环您的数据并获得最大时间值。 注：UDF仅供参考，可根据需要更改

  1. 如何遍历每一行中的每一列并获得最高的 TIME-VALUE 对？
scala> import org.apache.spark.sql.expressions.{UserDefinedFunction} 

scala> def MaxTime:UserDefinedFunction = udf((json:String) => {
   val pars = JSON.parseFull(json)
   var output=""
   pars.foreach{ x => val y = x.asInstanceOf[List[Any]]
     var i = 1
     var TimeMap = scala.collection.mutable.Map[String, Long]()
     var ValueMap = scala.collection.mutable.Map[String, Double]()
     y.foreach{ zz => val z =  zz.asInstanceOf[Map[String,Double]]
       TimeMap(i.toString) =  z("TIME").toLong
       ValueMap(i.toString) =  z("VALUE")
       i = i + 1
     }
   output = """[{"TIME" : """ + TimeMap.maxBy(_._2)._2.toString + """ ,"VALUE": """ + ValueMap(TimeMap.maxBy(_._2)._1) + """}]"""
  } 
output})

scala> SIGNALSFiltered.withColumn("SIG1", MaxTime(col("SIG1")).withColumn("SIG2", MaxTime(col("SIG2")))).withColumn("SIG3", MaxTime(col("SIG3"))).withColumn("SIG4", MaxTime(col("SIG4"))).show(false)
  1. 在每列（SIG1，....SIG4）中获得最高之后，只需更新其中最高的所有列中的 TIME 值。

像上面一样编写相同的 UDF，并将完整的行作为参数传递。然后将每个列值解析为 Map 并获取所有列中的最大值。

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