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[英]How to use orderby() with descending order in Spark window functions?
[英]In spark how to use window spec with aggregate functions
我有看起来像的火花数据框:
+------------+---------+---------------------------------------------------------------------------------------------------------+
|parent_key |id |value |raw_is_active |updated_at |
+------------+---------+------------------------------------------------------------+------------------------+-------------------+
|1 |2 |[, 0, USER, 2020-12-11 04:50:40, 2020-12-11 04:50:40,] |[2020-12-11 04:50:40, 0]|2020-12-11 04:50:40|
|1 |2 |[testA, 0, USER, 2020-12-11 04:50:40, 2020-12-11 17:18:00,] |null |2020-12-11 17:18:00|
|1 |2 |[testA, 0, USER, 2020-12-11 04:50:40, 2020-12-11 17:19:56,] |null |2020-12-11 17:19:56|
|1 |2 |[testA, 1, USER, 2020-12-11 04:50:40, 2020-12-11 17:20:24,] |[2020-12-11 17:20:24, 1]|2020-12-11 17:20:24|
|2 |3 |[testB, 0, USER, 2020-12-11 17:24:03, 2020-12-11 17:24:03,] |[2020-12-11 17:24:03, 0]|2020-12-11 17:24:03|
|3 |4 |[testC, 0, USER, 2020-12-11 17:27:36, 2020-12-11 17:27:36,] |[2020-12-11 17:27:36, 0]|2020-12-11 17:27:36|
+------------+---------+------------------------------------------------------------+------------------------+-------------------+
架构是:
root
|-- parent_key: long (nullable = true)
|-- id: string (nullable = true)
|-- value: struct (nullable = true)
| |-- first_name: string (nullable = true)
| |-- is_active: integer (nullable = true)
| |-- source: string (nullable = true)
| |-- created_at: timestamp (nullable = true)
| |-- updated_at: timestamp (nullable = true)
|-- raw_is_active: struct (nullable = true)
| |-- updated_at: timestamp (nullable = true)
| |-- value: integer (nullable = true)
|-- updated_at: timestamp (nullable = true)
我正在寻找 output:
+------------+---------+------------------------------------------------------------+---------------------------------------------------+-------------------+
|parent_key |id |value |raw_is_active |updated_at |
+------------+---------+---------------------------------------------------------------------------------------------------------+--------------------------+
|1 |2 |[testA, 1, USER, 2020-12-11 04:50:40, 2020-12-11 17:20:24] |[[2020-12-11 04:50:40, 0],[2020-12-11 17:20:24, 1]]|2020-12-11 04:50:40|
|2 |3 |[testB, 0, USER, 2020-12-11 17:24:03, 2020-12-11 17:24:03] |[2020-12-11 17:24:03, 0] |2020-12-11 17:24:03|
|3 |4 |[testC, 0, USER, 2020-12-11 17:27:36, 2020-12-11 17:27:36] |[2020-12-11 17:27:36, 0] |2020-12-11 17:27:36|
+------------+---------+---------------------------------------------------------------------------------------------------------+--------------------------+
因此,在updated_at
列的基础上,我想保留最新的行,并且还想为给定id
的所有行创建raw_is_active
数组。
我知道我可以使用代码选择最新value
:
val windowSpec = Window.partitionBy("id").orderBy(col("updated_at").desc)
dataFrame
.withColumn("maxTS", first("updated_at").over(windowSpec))
.select("*").where(col("maxTS") === col("updated_at"))
.drop("maxTS")
但不确定我如何也可以为raw_is_active
列创建一个集合。
或者我可以完全按 function 使用 group,例如:
dataFrame
.groupBy("parent_key", "id")
.agg(collect_list("value") as "value_list", collect_set("raw_is_active") as "active_list")
.withColumn("value", col("value_list")(size(col("value_list")).minus(1)))
.drop("value_list")
对于上述我不确定
.withColumn("value", col("value_list")(size(col("value_list")).minus(1)))
总是会给我最新的值collect_list
和collect_set
,这段代码有效吗?更新感谢@mck,我能够让它与代码一起工作:
val windowSpec = Window.partitionBy("id").orderBy(col("updated_at").desc)
val windowSpecSet = Window.partitionBy("id").orderBy(col("updated_at"))
val df2 = dataFrame.withColumn(
"rn",
row_number().over(windowSpec)
).withColumn(
"active_list",
collect_set("raw_is_active").over(windowSpecSet)
).drop("raw_is_active").filter("rn = 1")
但是,该代码比我现有的代码花费更多时间:
dataFrame
.groupBy("parent_key", "id")
.agg(collect_list("value") as "value_list", collect_set("raw_is_active") as "active_list")
.withColumn("value", col("value_list")(size(col("value_list")).minus(1)))
.drop("value_list")
我的印象是 window function 会比groupBy
和agg
表现更好。
为每个 id 分区中的每一行分配一个row_number
并过滤row_number = 1
的行:
val windowSpec = Window.partitionBy("id").orderBy(col("updated_at").desc)
val df2 = dataFrame.withColumn(
"rn",
row_number().over(windowSpec)
).withColumn(
"active_list",
array_sort(collect_set("raw_is_active").over(windowSpec))
).drop("raw_is_active").filter("rn = 1")
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