Scala-如何将字符串值传递到数据帧过滤器（Spark-Shell）

Question

I am using Spark 2.2.0 and Scala 2.11.8 in the Spark-Shell environment. I have a data frame df, and I need to filter out the previous day's data based on the value of column 'date' and then append the data to a HDFS location. (eg today is 2018-06-28, I need the data of 2018-06-27)

Below is the code:

 df.filter($"date" === "2018-06-27") .write.mode(SaveMode.Append).parquet("hdfs:/path..../date=2018-06-27")

I need the code above for automation, so I need to replace "2018-06-27" for the filter value as well as the directory name. So if I have a string -> date_test: String = 2018-06-27; The code below should be still working

 df.filter($"date" === "date_test") .write.mode(SaveMode.Append).parquet("hdfs:/path..../date=date_test")

How to do this?

Answer 1

You can apply filter conditions like below

//Input
+----------+
|      date|
+----------+
|2018-02-01|
|2017-01-02|
+----------+

//Solution: 
 val previousDate="'2018-02-01'"
 df.filter(s"date=$previousDate").show

//Output: 
+----------+
|      date|
+----------+
|2018-02-01|
+----------+

You can do like this for your solution

 val datetest:String="2018-02-01"
 df.filter(s"date='$datetest'").write.mode(SaveMode.Append).parquet(s"hdfs:/path..../$datetest")