如何根据传递的参数从RDD中提取值

+-----------------+-----------------+-------------+
|Merchant_Name    |Display_Name     |Store_ID_name|
+-----------------+-----------------+-------------+
|Fitch            |Fitch            |null         |
|Kids             |Kids             |null         |
|Ace Hardware     |Ace Hardware     |null         |
| Fresh Market    |Acme  Market     |Acme Markets |
|Adventure        | Island          |null         |
+-----------------+-----------------+-------------+

可以用字符串参数编写函数

import org.apache.spark.sql.functions._
def filterRowsWithKey(key: String) = df.filter(col("Merchant_Name") === key).select("Display_Name", "Store_ID_name")

并将函数调用为

filterRowsWithKey("Fitch").show(false)

会给你

+------------+-------------+
|Display_Name|Store_ID_name|
+------------+-------------+
|Fitch       |null         |
+------------+-------------+

我希望答案有帮助

更新

如果希望第一行作为字符串从函数返回,则可以这样做

import org.apache.spark.sql.functions._
def filterRowsWithKey(key: String) = df.filter(col("Merchant_Name") === key).select("Display_Name", "Store_ID_name").first().mkString(",")

println(filterRowsWithKey("Fitch"))

哪个应该给你

Fitch,null

如果找不到传递的键,上面的函数将引发异常,因此为了安全起见,可以使用以下函数

import org.apache.spark.sql.functions._
def filterRowsWithKey(key: String) = {
  val filteredDF = df.filter(col("Merchant_Name") === key).select("Display_Name", "Store_ID_name")
  if(filteredDF.count() > 0) filteredDF.first().mkString(",") else "key not found"
}