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我有一个csv文件。它有很多列,其中两个是Month和Year。月份表示为1 ... 12,而2013年(例如)。我需要创建一个格式为mm/yyyy的时间戳作为新列,比如'timestamp'。我尝试了下面的代码片段,但失败了。使用unix_timestamp方法在spark中创建时间戳
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里我错了吗?