在spark中，如何从结构中抽象数组并用它创建一个新字段

Question

我有一个架构为的结构

root
|-- id: long (nullable = true)
|-- products: array (nullable = true)
|    |-- element: struct (containsNull = true)
|    |    |-- id: integer (nullable = true)
|    |    |-- name: string (nullable = true)
|    |    |-- created_at: long (nullable = true)
|    |    |-- updated_at: long (nullable = true)
|    |    |-- product_color: array (nullable = true)
|    |    |    |-- element: struct (containsNull = true)
|    |    |    |    |-- id: integer (nullable = true)
|    |    |    |    |-- color: string (nullable = true)
|    |    |    |    |-- created_at: long (nullable = true)
|    |    |    |    |-- updated_at: long (nullable = true)
|    |    |    |    |-- products_id: long (nullable = true)
|    |    |-- orders_id: long (nullable = true)

现在，我想用product_color创建一个新列，所以在我的数据框架中，我添加了一个像这样的新列

df.withColumn("product_color", col(currentNode + "." + fieldName))

有了新的列模式：

root
|-- id: long (nullable = true)
|-- products: array (nullable = true)
|    |-- element: struct (containsNull = true)
|    |    |-- id: integer (nullable = true)
|    |    |-- name: string (nullable = true)
|    |    |-- created_at: long (nullable = true)
|    |    |-- updated_at: long (nullable = true)
|    |    |-- product_color: array (nullable = true)
|    |    |    |-- element: struct (containsNull = true)
|    |    |    |    |-- id: integer (nullable = true)
|    |    |    |    |-- color: string (nullable = true)
|    |    |    |    |-- created_at: long (nullable = true)
|    |    |    |    |-- updated_at: long (nullable = true)
|    |    |    |    |-- products_id: long (nullable = true)
|    |    |-- orders_id: long (nullable = true)
|-- product_color: array (nullable = true)
|    |-- element: array (containsNull = true)
|    |    |-- element: struct (containsNull = true)
|    |    |    |-- id: integer (nullable = true)
|    |    |    |-- color: string (nullable = true)
|    |    |    |-- created_at: long (nullable = true)
|    |    |    |-- updated_at: long (nullable = true)
|    |    |    |-- products_id: long (nullable = true)

如果查看product_color的模式，则会添加数组的一个元素。

|-- element: array (containsNull = true)

我正在寻求帮助，以了解如何使用产品结构中的确切模式创建新列。

预期架构：

root
|-- id: long (nullable = true)
|-- products: array (nullable = true)
|    |-- element: struct (containsNull = true)
|    |    |-- id: integer (nullable = true)
|    |    |-- name: string (nullable = true)
|    |    |-- created_at: long (nullable = true)
|    |    |-- updated_at: long (nullable = true)
|    |    |-- product_color: array (nullable = true)
|    |    |    |-- element: struct (containsNull = true)
|    |    |    |    |-- id: integer (nullable = true)
|    |    |    |    |-- color: string (nullable = true)
|    |    |    |    |-- created_at: long (nullable = true)
|    |    |    |    |-- updated_at: long (nullable = true)
|    |    |    |    |-- products_id: long (nullable = true)
|    |    |-- orders_id: long (nullable = true)
|-- product_color: array (nullable = true)
|    |-- element: struct (containsNull = true)
|    |    |-- id: integer (nullable = true)
|    |    |-- color: string (nullable = true)
|    |    |-- created_at: long (nullable = true)
|    |    |-- updated_at: long (nullable = true)
|    |    |-- products_id: long (nullable = true)

火花：2.4.5语言：Scala

Answer 1

添加为new column时，分解数组以获得所需的模式。

Example:

//sample df schema
df.printSchema
//root
// |-- id: long (nullable = true)
// |-- products: array (nullable = true)
// |    |-- element: struct (containsNull = true)
// |    |    |-- id: long (nullable = true)
// |    |    |-- order_id: long (nullable = true)
// |    |    |-- product_color: array (nullable = true)
// |    |    |    |-- element: struct (containsNull = true)
// |    |    |    |    |-- color: string (nullable = true)
// |    |    |    |    |-- id: long (nullable = true)
// |    |    |    |    |-- products_id: long (nullable = true)
df.withColumn("product_color",explode(col("products.product_color"))).printSchema
//root
// |-- id: long (nullable = true)
// |-- products: array (nullable = true)
// |    |-- element: struct (containsNull = true)
// |    |    |-- id: long (nullable = true)
// |    |    |-- order_id: long (nullable = true)
// |    |    |-- product_color: array (nullable = true)
// |    |    |    |-- element: struct (containsNull = true)
// |    |    |    |    |-- color: string (nullable = true)
// |    |    |    |    |-- id: long (nullable = true)
// |    |    |    |    |-- products_id: long (nullable = true)
// |-- product_color: array (nullable = true)
// |    |-- element: struct (containsNull = true)
// |    |    |-- color: string (nullable = true)
// |    |    |-- id: long (nullable = true)
// |    |    |-- products_id: long (nullable = true)