如何从火花数据框中过滤掉空值 [英] how to filter out a null value from spark dataframe
问题描述
我使用以下架构在 spark 中创建了一个数据框:
I created a dataframe in spark with the following schema:
root
|-- user_id: long (nullable = false)
|-- event_id: long (nullable = false)
|-- invited: integer (nullable = false)
|-- day_diff: long (nullable = true)
|-- interested: integer (nullable = false)
|-- event_owner: long (nullable = false)
|-- friend_id: long (nullable = false)
数据如下:
+----------+----------+-------+--------+----------+-----------+---------+
| user_id| event_id|invited|day_diff|interested|event_owner|friend_id|
+----------+----------+-------+--------+----------+-----------+---------+
| 4236494| 110357109| 0| -1| 0| 937597069| null|
| 78065188| 498404626| 0| 0| 0| 2904922087| null|
| 282487230|2520855981| 0| 28| 0| 3749735525| null|
| 335269852|1641491432| 0| 2| 0| 1490350911| null|
| 437050836|1238456614| 0| 2| 0| 991277599| null|
| 447244169|2095085551| 0| -1| 0| 1579858878| null|
| 516353916|1076364848| 0| 3| 1| 3597645735| null|
| 528218683|1151525474| 0| 1| 0| 3433080956| null|
| 531967718|3632072502| 0| 1| 0| 3863085861| null|
| 627948360|2823119321| 0| 0| 0| 4092665803| null|
| 811791433|3513954032| 0| 2| 0| 415464198| null|
| 830686203| 99027353| 0| 0| 0| 3549822604| null|
|1008893291|1115453150| 0| 2| 0| 2245155244| null|
|1239364869|2824096896| 0| 2| 1| 2579294650| null|
|1287950172|1076364848| 0| 0| 0| 3597645735| null|
|1345896548|2658555390| 0| 1| 0| 2025118823| null|
|1354205322|2564682277| 0| 3| 0| 2563033185| null|
|1408344828|1255629030| 0| -1| 1| 804901063| null|
|1452633375|1334001859| 0| 4| 0| 1488588320| null|
|1625052108|3297535757| 0| 3| 0| 1972598895| null|
+----------+----------+-------+--------+----------+-----------+---------+
我想过滤掉friend_id"字段中有空值的行.
I want to filter out the rows have null values in the field of "friend_id".
scala> val aaa = test.filter("friend_id is null")
scala> aaa.count
我得到 :res52: Long = 0 这显然不对.获得它的正确方法是什么?
I got :res52: Long = 0 which is obvious not right. What is the right way to get it?
还有一个问题，我想替换friend_id字段中的值.我想用 0 和 1 替换 null 以替换除 null 之外的任何其他值.我能弄清楚的代码是:
One more question, I want to replace the values in the friend_id field. I want to replace null with 0 and 1 for any other value except null. The code I can figure out is:
val aaa = train_friend_join.select($"user_id", $"event_id", $"invited", $"day_diff", $"interested", $"event_owner", ($"friend_id" != null)?1:0)
此代码也不起作用.谁能告诉我我该如何修复它?谢谢
This code also doesn't work. Can anyone tell me how can I fix it? Thanks
推荐答案
假设您设置了此数据(以便结果可重现):
Let's say you have this data setup (so that results are reproducible):
// declaring data types
case class Company(cName: String, cId: String, details: String)
case class Employee(name: String, id: String, email: String, company: Company)
// setting up example data
val e1 = Employee("n1", null, "n1@c1.com", Company("c1", "1", "d1"))
val e2 = Employee("n2", "2", "n2@c1.com", Company("c1", "1", "d1"))
val e3 = Employee("n3", "3", "n3@c1.com", Company("c1", "1", "d1"))
val e4 = Employee("n4", "4", "n4@c2.com", Company("c2", "2", "d2"))
val e5 = Employee("n5", null, "n5@c2.com", Company("c2", "2", "d2"))
val e6 = Employee("n6", "6", "n6@c2.com", Company("c2", "2", "d2"))
val e7 = Employee("n7", "7", "n7@c3.com", Company("c3", "3", "d3"))
val e8 = Employee("n8", "8", "n8@c3.com", Company("c3", "3", "d3"))
val employees = Seq(e1, e2, e3, e4, e5, e6, e7, e8)
val df = sc.parallelize(employees).toDF
数据为:
+----+----+---------+---------+
|name| id| email| company|
+----+----+---------+---------+
| n1|null|n1@c1.com|[c1,1,d1]|
| n2| 2|n2@c1.com|[c1,1,d1]|
| n3| 3|n3@c1.com|[c1,1,d1]|
| n4| 4|n4@c2.com|[c2,2,d2]|
| n5|null|n5@c2.com|[c2,2,d2]|
| n6| 6|n6@c2.com|[c2,2,d2]|
| n7| 7|n7@c3.com|[c3,3,d3]|
| n8| 8|n8@c3.com|[c3,3,d3]|
+----+----+---------+---------+
现在要过滤带有 null id 的员工，您将执行 --
Now to filter employees with null ids, you will do --
df.filter("id is null").show
这将正确显示以下内容:
which will correctly show you following:
+----+----+---------+---------+
|name| id| email| company|
+----+----+---------+---------+
| n1|null|n1@c1.com|[c1,1,d1]|
| n5|null|n5@c2.com|[c2,2,d2]|
+----+----+---------+---------+
进入问题的第二部分，您可以将 null id 替换为 0，将其他值替换为 1 --
Coming to the second part of your question, you can replace the null ids with 0 and other values with 1 with this --
df.withColumn("id", when($"id".isNull, 0).otherwise(1)).show
结果:
+----+---+---------+---------+
|name| id| email| company|
+----+---+---------+---------+
| n1| 0|n1@c1.com|[c1,1,d1]|
| n2| 1|n2@c1.com|[c1,1,d1]|
| n3| 1|n3@c1.com|[c1,1,d1]|
| n4| 1|n4@c2.com|[c2,2,d2]|
| n5| 0|n5@c2.com|[c2,2,d2]|
| n6| 1|n6@c2.com|[c2,2,d2]|
| n7| 1|n7@c3.com|[c3,3,d3]|
| n8| 1|n8@c3.com|[c3,3,d3]|
+----+---+---------+---------+
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