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From Andrés Doncel Ramírez (JIRA) <j...@apache.org>
Subject [jira] [Created] (SPARK-26869) UDF with struct requires to have _1 and _2 as struct field names
Date Wed, 13 Feb 2019 12:04:00 GMT
Andrés Doncel Ramírez created SPARK-26869:
---------------------------------------------

             Summary: UDF with struct requires to have _1 and _2 as struct field names
                 Key: SPARK-26869
                 URL: https://issues.apache.org/jira/browse/SPARK-26869
             Project: Spark
          Issue Type: Bug
          Components: SQL
    Affects Versions: 2.4.0, 2.3.0
         Environment: Ubuntu 18.04.1 LTS
            Reporter: Andrés Doncel Ramírez


When using a UDF which has a Seq of tuples as input, the struct field names need to match
"_1" and "_2". The following code illustrates this.

 
{code:java}
val df = sc.parallelize(Array(
  ("1",3.0),
  ("2",4.5),
  ("5",2.0)
)
).toDF("c1","c2")

val df1=df.agg(collect_list(struct("c1","c2")).as("c3"))
// Changing column names to _1 and _2 when creating the struct
val df2=df.agg(collect_list(struct(col("c1").as("_1"),col("c2").as("_2"))).as("c3"))

def takeUDF = udf({ (xs: Seq[(String, Double)]) =>
  xs.take(2)
})

df1.printSchema
df2.printSchema

df1.withColumn("c4",takeUDF(col("c3"))).show() // this fails

df2.withColumn("c4",takeUDF(col("c3"))).show() // this works
{code}
The first one returns the following exception:

org.apache.spark.sql.AnalysisException: cannot resolve 'UDF(c3)' due to data type mismatch:
argument 1 requires array<struct<_1:string,_2:double>> type, however, '`c3`' is
of array<struct<c1:string,c2:double>> type.;;

While the second works as expected and prints the result.



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