How to use array type column value in CASE statement

问题

I have a dataframe with two columns, listA stored as Seq[String] and valB stored as String. I want to create a third column valC, which will be of Int type and its value is
iff valB is present in listA then 1 otherwise 0

I tried doing the following:

val dfWithAdditionalColumn = df.withColumn("valC", when($"listA".contains($"valB"), 1).otherwise(0))

But Spark failed to execute this and gave the following error:

cannot resolve 'contains('listA', 'valB')' due to data type mismatch: argument 1 requires string type, however, 'listA' is of array type.;

How do I use a array type column value in CASE statement?

Thanks, Devj

回答1:

You can write a simple udf that will check if the element is present in the array :

val arrayContains = udf( (col1: Int, col2: Seq[Int]) => if(col2.contains(col1) ) 1 else 0 )

And then just call it and pass the necessary columns in the correct order :

df.withColumn("hasAInB", arrayContains($"a", $"b" ) ).show

+---+---------+-------+
|  a|        b|hasAInB|
+---+---------+-------+
|  1|   [1, 2]|      1|
|  2|[2, 3, 4]|      1|
|  3|   [1, 4]|      0|
+---+---------+-------+

回答2:

You should use array_contains:

import org.apache.spark.sql.functions.{expr, array_contains}

df.withColumn("valC", when(expr("array_contains(listA, valB)"), 1).otherwise(0))

来源：https://stackoverflow.com/questions/46220883/how-to-use-array-type-column-value-in-case-statement