Spark:数据帧中zipwithindex的等效项 [英] Spark: equivelant of zipwithindex in dataframe

问题描述

假设我有以下数据框:

dummy_data = [('a',1),('b',25),('c',3),('d',8),('e',1)]
df = sc.parallelize(dummy_data).toDF(['letter','number'])

我想创建以下数据框:

[('a',0),('b',2),('c',1),('d',3),('e',0)]

我所做的是将其转换为 rdd 并使用 zipWithIndex 函数并加入结果后:

What I do is to convert it to rdd and use zipWithIndex function and after join the results:

convertDF = (df.select('number')
              .distinct()
              .rdd
              .zipWithIndex()
              .map(lambda x:(x[0].number,x[1]))
              .toDF(['old','new']))


finalDF = (df
            .join(convertDF,df.number == convertDF.old)
            .select(df.letter,convertDF.new))

数据帧中是否有与 zipWIthIndex 类似的功能?还有其他更有效的方法来完成这项任务吗?

Is if there is something similar function as zipWIthIndex in dataframes? Is there another more efficient way to do this task?

推荐答案

请查看 https://issues.apache.org/jira/browse/SPARK-23074 对于数据帧中的这种直接功能奇偶校验.. 如果您有兴趣在 Spark 的某个时候看到这一点，请对该 jira 点赞.

Please check https://issues.apache.org/jira/browse/SPARK-23074 for this direct functionality parity in dataframes .. upvote that jira if you're interested to see this at some point in Spark.

这是 PySpark 中的一种解决方法:

Here's a workaround though in PySpark:

def dfZipWithIndex (df, offset=1, colName="rowId"):
    '''
        Enumerates dataframe rows is native order, like rdd.ZipWithIndex(), but on a dataframe 
        and preserves a schema

        :param df: source dataframe
        :param offset: adjustment to zipWithIndex()'s index
        :param colName: name of the index column
    '''

    new_schema = StructType(
                    [StructField(colName,LongType(),True)]        # new added field in front
                    + df.schema.fields                            # previous schema
                )

    zipped_rdd = df.rdd.zipWithIndex()

    new_rdd = zipped_rdd.map(lambda args: ([args[1] + offset] + list(args[0])))

    return spark.createDataFrame(new_rdd, new_schema)

这也可以在 包.

That's also available in abalon package.

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