#subtractByKey去除x中那些key也在y中的元素 x = sc.parallelize([("a",1),("b",2),("c",3)]) y = sc.parallelize([("a",2),("b",(1,2))]) x.subtractByKey(y).collect() [('c', 3)] #foldByKey的操作和reduceByKey类似,但是要提供一个初始值 x = sc.parallelize([("a",1)...
我们将两个参数函数应用为匿名的lambda函数到reduce调用如下: list_rdd.reduce(lambdaa, b: a+b) 在这里,lambda接受两个参数a和b。它简单地将这两个数字相加,因此a+b,并返回输出。通过RDD的reduce调用,我们可以依次将 RDD 列表的前两个数字相加,返回结果,然后将第三个数字添加到结果中,依此类推。因此,最终,...
常用PairrDD的转换操作 PairRDD指的是数据为长度为2的tuple类似(k,v)结构的数据类型的RDD,其每个数据的第一个元素被当做key,第二个元素被当做value. 1 reduceByKey对相同的key对应的values应用二元归并操作 2 groupByKey将相同的key对应的values收集成一个Iterator 迭代器 3 sortByKey按照key排序,可以指定是否降...
reduceByKey由于自带聚合逻辑,所以会现在分区内做预聚合,然后再走分组流程,分组后再做最终聚合 对于groupByKey算子,reduceByKey最大的提升在于,分组前进行了预聚合,那么在shuffle分组节点,被shuffle的数据可以极大的减少,提升了性能。因此分组+聚合,首先reduceBykey算子。 2.3 分区设置算子 glom:将RDD的数据,加上嵌套,...
Key actions include collect, count, take, reduce, foreach, first, takeOrdered, takeSample, countByKey, saveAsTextFile, saveAsSequenceFile, saveAsObjectFile, foreachPartition, collectAsMap, aggregate, and fold. These actions initiate execution and materialize RDD data. Remember any RDD operation ...
foldByKey foldByKey x = sc.parallelize([('B',1),('B',2),('A',3),('A',4),('A',5)]) zeroValue = 1 # one is 'zero value' for multiplication y = x.foldByKey(zeroValue,lambda agg,x: agg*x ) # computes cumulative product within each key ...
countsRDD=stringRDD.map(lambda word:(word,1)).reduceByKey(lambda x,y : x+y) countsRDD.saveAsTextFile("data/output") 2、在eplicesIDE上编写wordcount.py ,用spark-submit在终端执行程序时也出现同样的问题。 在终端输入 spark-submit --driver-memory 2g --master local[4] WordCount.py ...
countByKey # countByKey x = sc.parallelize([('B',1),('B',2),('A',3),('A',4),('A',5)]) y = x.countByKey() print(x.collect()) print(y) [('B ', 1), ('B ', 2), ('A ', 3), ('A ', 4), ('A
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fold – action fold()– Aggregate the elements of each partition, and then the results for all the partitions. #fold from operator import add foldRes=listRdd.fold(0, add) print(foldRes) reduce reduce()– Reduces the elements of the dataset using the specified binary operator. ...