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pyspark:在窗口上统计

我刚尝试在窗口上执行countDistinct并出现此错误:

AnalysisException: u'Distinct window functions are not supported: count(distinct color#1926)
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有没有办法在pyspark中对窗口进行明确计数?

这是一些示例代码:

from pyspark.sql.window import Window    
from pyspark.sql import functions as F

#function to calculate number of seconds from number of days
days = lambda i: i * 86400

df = spark.createDataFrame([(17, "2017-03-10T15:27:18+00:00", "orange"),
                    (13, "2017-03-15T12:27:18+00:00", "red"),
                    (25, "2017-03-18T11:27:18+00:00", "red")],
                    ["dollars", "timestampGMT", "color"])

df = df.withColumn('timestampGMT', df.timestampGMT.cast('timestamp'))

#create window by casting timestamp to long (number of seconds)
w = (Window.orderBy(F.col("timestampGMT").cast('long')).rangeBetween(-days(7), 0))

df = df.withColumn('distinct_color_count_over_the_last_week', F.countDistinct("color").over(w))

df.show()
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这是我想看到的输出:

+-------+--------------------+------+---------------------------------------+
|dollars|        timestampGMT| …
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count distinct-values window-functions pyspark

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