list - pysparkcollect_set或collect_list与groupby

Question

如何在 groupby 之后的数据帧上使用 collect_set 或 collect_list。例如:df.groupby('key').collect_set('values')。我收到错误:AttributeError:“GroupedData”对象没有属性“collect_set”

Answer 1

您需要使用 agg。示例:

from pyspark import SparkContext
from pyspark.sql import HiveContext
from pyspark.sql import functions as F

sc = SparkContext("local")

sqlContext = HiveContext(sc)

df = sqlContext.createDataFrame([
    ("a", None, None),
    ("a", "code1", None),
    ("a", "code2", "name2"),
], ["id", "code", "name"])

df.show()

+---+-----+-----+
| id| code| name|
+---+-----+-----+
|  a| null| null|
|  a|code1| null|
|  a|code2|name2|
+---+-----+-----+

请注意，在上面您必须创建一个 HiveContext。请参阅https://stackoverflow.com/a/35529093/690430用于处理不同的 Spark 版本。

(df
  .groupby("id")
  .agg(F.collect_set("code"),
       F.collect_list("name"))
  .show())

+---+-----------------+------------------+
| id|collect_set(code)|collect_list(name)|
+---+-----------------+------------------+
|  a|   [code1, code2]|           [name2]|
+---+-----------------+------------------+