带3个参数的zip功能

Question

我想在Spark SQL表中转置多个列 我发现这个解决方案只有两列，我想知道如何使用zip列函数与三列varA, varB and varC.

import org.apache.spark.sql.functions.{udf, explode}

val zip = udf((xs: Seq[Long], ys: Seq[Long]) => xs.zip(ys))

df.withColumn("vars", explode(zip($"varA", $"varB"))).select(
   $"userId", $"someString",
   $"vars._1".alias("varA"), $"vars._2".alias("varB")).show

这是我的数据帧架构：

`root
 |-- owningcustomerid: string (nullable = true)
 |-- event_stoptime: string (nullable = true)
 |-- balancename: string (nullable = false)
 |-- chargedvalue: string (nullable = false)
 |-- newbalance: string (nullable = false)
`

我试过这段代码：

    val zip = udf((xs: Seq[String], ys: Seq[String], zs: Seq[String]) => (xs, ys, zs).zipped.toSeq)

df.printSchema

val df4=df.withColumn("vars", explode(zip($"balancename", $"chargedvalue",$"newbalance"))).select(
   $"owningcustomerid", $"event_stoptime",
   $"vars._1".alias("balancename"), $"vars._2".alias("chargedvalue"),$"vars._2".alias("newbalance"))

我收到了这个错误：

cannot resolve 'UDF(balancename, chargedvalue, newbalance)' due to data type mismatch: argument 1 requires array<string> type, however, '`balancename`' is of string type. argument 2 requires array<string> type, however, '`chargedvalue`' is of string type. argument 3 requires array<string> type, however, '`newbalance`' is of string type.;;

'项目[拥有客户＃1085，event_stoptime＃1086，balancename＃1159，chargevalue＃1160，newbalance＃1161，爆炸（UDF（​​平衡名称＃1159，chargevalue＃1160，newbalance＃1161））AS vars＃1167]

Answer 1

在Scala中，你可以使用Tuple3.zipped

val zip = udf((xs: Seq[Long], ys: Seq[Long], zs: Seq[Long]) => 
  (xs, ys, zs).zipped.toSeq)

zip($"varA", $"varB", $"varC")

特别是在Spark SQL（> = 2.4）中，您可以使用arrays_zip函数：

import org.apache.spark.sql.functions.arrays_zip

arrays_zip($"varA", $"varB", $"varC")

但是你必须注意你的数据不包含array<string>但是包含普通的strings - 因此不允许使用Spark arrays_zip或explode，你应该首先解析你的数据。