Big data: wordcount case RDD programming operator, countByKey, reduce, fold, first, take, top, count, takeSample, takeOrdered

Big data: wordcount case review RDD programming operator

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Big data: wordcount case review RDD programming operator

Filter
and then combine,
just take the binary group and
splicing

countByKey counts key occurrences

Words are respelled into words, counting 1
and then counting

dict,
it is not an RDD, it
is already an action,

it is an action operator

The reduce operator

is not an RDD return value. It
is different from the previous reduceByKey.

The aggregation method is the same as it


. The initial value will be added when it works within a partition or between partitions.

Use less

first, the return is not an RDD, but a specific element



take, the first n

items are returned, the list is sorted in

descending order
, and then the first n

elements are taken for internal comparison.
Others need to customize the comparison method. The first parameter of




gg is not allowed to say that the position is repeated.


, rather than the element itself

The default is ascending.
Under normal circumstances, you can change the number

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Summarize

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1)
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