scala - scala spark UDF过滤器数组的结构

问题描述

我有一个带有架构的数据框

root
 |-- x: Long (nullable = false)
 |-- y: Long (nullable = false)
 |-- features: array (nullable = true)
 |    |-- element: struct (containsNull = true)
 |    |    |-- name: string (nullable = true)
 |    |    |-- score: double (nullable = true)

例如，我有数据

+--------------------+--------------------+------------------------------------------+
|                x   |              y     |       features                           |
+--------------------+--------------------+------------------------------------------+
|10                  |          9         |[["f1", 5.9], ["ft2", 6.0], ["ft3", 10.9]]|
|11                  |          0         |[["f4", 0.9], ["ft1", 4.0], ["ft2", 0.9] ]|
|20                  |          9         |[["f5", 5.9], ["ft2", 6.4], ["ft3", 1.9] ]|
|18                  |          8         |[["f1", 5.9], ["ft4", 8.1], ["ft2", 18.9]]|
+--------------------+--------------------+------------------------------------------+

我想过滤带有特定前缀的功能，比如“ft”，所以最终我想要结果：

+--------------------+--------------------+-----------------------------+
|                x   |              y     |       features              |
+--------------------+--------------------+-----------------------------+
|10                  |          9         |[["ft2", 6.0], ["ft3", 10.9]]|
|11                  |          0         |[["ft1", 4.0], ["ft2", 0.9] ]|
|20                  |          9         |[["ft2", 6.4], ["ft3", 1.9] ]|
|18                  |          8         |[["ft4", 8.1], ["ft2", 18.9]]|
+--------------------+--------------------+-----------------------------+

我没有使用 Spark 2.4+，所以我不能使用这里提供的解决方案：Spark (Scala) filter array of structs without explode

我尝试使用 UDF，但仍然无法正常工作。这是我的尝试。我定义了一个 UDF：

def filterFeature: UserDefinedFunction = 
udf((features: Seq[Row]) =>
    features.filter{
        x.getString(0).startsWith("ft")
    }
)

但是如果我应用这个 UDF

df.withColumn("filtered", filterFeature($"features"))

我得到错误Schema for type org.apache.spark.sql.Row is not supported。我发现我无法Row从 UDF 返回。然后我尝试了

def filterFeature: UserDefinedFunction = 
udf((features: Seq[Row]) =>
    features.filter{
        x.getString(0).startsWith("ft")
    }, (StringType, DoubleType)
)

然后我得到一个错误：

 error: type mismatch;
 found   : (org.apache.spark.sql.types.StringType.type, org.apache.spark.sql.types.DoubleType.type)
 required: org.apache.spark.sql.types.DataType
              }, (StringType, DoubleType)
                 ^

我还按照一些答案的建议尝试了一个案例类：

case class FilteredFeature(featureName: String, featureScore: Double)
def filterFeature: UserDefinedFunction = 
udf((features: Seq[Row]) =>
    features.filter{
        x.getString(0).startsWith("ft")
    }, FilteredFeature
)

但我得到了：

 error: type mismatch;
 found   : FilteredFeature.type
 required: org.apache.spark.sql.types.DataType
              }, FilteredFeature
                 ^

我试过了：

case class FilteredFeature(featureName: String, featureScore: Double)
def filterFeature: UserDefinedFunction = 
udf((features: Seq[Row]) =>
    features.filter{
        x.getString(0).startsWith("ft")
    }, Seq[FilteredFeature]
)

我有：

<console>:192: error: missing argument list for method apply in class GenericCompanion
Unapplied methods are only converted to functions when a function type is expected.
You can make this conversion explicit by writing `apply _` or `apply(_)` instead of `apply`.
              }, Seq[FilteredFeature]
                    ^

我试过了：

case class FilteredFeature(featureName: String, featureScore: Double)
def filterFeature: UserDefinedFunction = 
udf((features: Seq[Row]) =>
    features.filter{
        x.getString(0).startsWith("ft")
    }, Seq[FilteredFeature](_)
)

我有：

<console>:201: error: type mismatch;
 found   : Seq[FilteredFeature]
 required: FilteredFeature
              }, Seq[FilteredFeature](_)
                          ^

在这种情况下我该怎么办？

标签： scalaapache-sparkapache-spark-sql

scala - scala spark UDF过滤器数组的结构

问题描述

解决方案

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