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我有一個csv文件。它有很多列,其中兩個是Month和Year。月份表示爲1 ... 12,而2013年(例如)。我需要創建一個格式爲mm/yyyy的時間戳作爲新列,比如'timestamp'。我嘗試了下面的代碼片段,但失敗了。使用unix_timestamp方法在spark中創建時間戳
scala> val df = spark.read.format("csv").option("header",
"true").load("/user/bala/*.csv")
df: org.apache.spark.sql.DataFrame = [_c0: string, Month: string ... 28
more fields]
scala> val df = spark.read.format("csv").option("header",
"true").load("/user/bala/AWI/*.csv")
df: org.apache.spark.sql.DataFrame = [_c0: string, Month: string ... 28
more fields]
scala> import org.apache.spark.sql.functions.udf
import org.apache.spark.sql.functions.udf
scala> def makeDT(Month: String, Year: String) = s"$Month $Year"
makeDT: (Month: String, Year: String)String
scala> val makeDt = udf(makeDT(_:String,_:String))
makeDt: org.apache.spark.sql.expressions.UserDefinedFunction =
UserDefinedFunction(<function2>,StringType,Some(List(StringType,
StringType)))
scala> df.select($"Month", $"Year", unix_timestamp(makeDt($"Month",
$"Year"), "mm/yyyy")).show(2)
+-----+----+-----------------------------------------+
|Month|Year|unix_timestamp(UDF(Month, Year), mm/yyyy)|
+-----+----+-----------------------------------------+
| 1|2013| null|
| 1|2013| null|
+-----+----+-----------------------------------------+
only showing top 2 rows
scala>
有人可以指出我在哪裏我錯了嗎?