在Spark Dataframe中的窗口上方创建组ID [英] Create a group id over a window in Spark Dataframe

问题描述

我有一个数据框，我想在每个Window分区中提供ID.例如，我有

I have a dataframe where I want to give id's in each Window partition. For example I have

id | col |
1  |  a  |
2  |  a  |
3  |  b  |
4  |  c  |
5  |  c  |

所以我要(基于与col列分组)

So I want (based on grouping with column col)

id | group |
1  |  1    |
2  |  1    |
3  |  2    |
4  |  3    |
5  |  3    |

我想使用窗口函数，但是我仍然找不到为每个窗口分配ID的方法.我需要类似的东西:

I want to use a window function but I cannot find anyway to assign an Id to each window. I need something like:

w = Window().partitionBy('col')
df = df.withColumn("group", id().over(w)) 

有什么办法可以达到这样的目标吗? (我不能简单地将col用作组ID，因为我有兴趣在多个列上创建一个窗口)

Is there any way to achive somethong like that. (I cannot simply use col as a group id because I am interested in creating a window over multiple columns)

推荐答案

在Window函数上简单地使用dense_rank 内置函数应该会为您提供所需的结果

Simply using a dense_rank inbuilt function over Window function should give you your desired result as

from pyspark.sql import window as W
import pyspark.sql.functions as f
df.select('id', f.dense_rank().over(W.Window.orderBy('col')).alias('group')).show(truncate=False)

应该给您

+---+-----+
|id |group|
+---+-----+
|1  |1    |
|2  |1    |
|3  |2    |
|4  |3    |
|5  |3    |
+---+-----+

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