Github user koertkuipers commented on the issue:
https://github.com/apache/spark/pull/13526
if they chain like that then i think i know how to do the optimization.
but do they? look for example at dataset.groupByKey(...).mapValues(...)
Dataset[T].groupByKey[K] uses function T => K and creates
KeyValueGroupedDataset[K, T]
KeyValueGroupedDataset[K, T].mapValues[W] uses function T => W and creates
KeyValueGroupedDataset[K, W]
so i have T => K and then T => W
On Thu, Oct 20, 2016 at 8:26 PM, Wenchen Fan <[email protected]>
wrote:
> 2 chained AppendColumns will have 2 functions: T => U and U => W, so we
> can combine them this way:
> convert UnsafeRow to T
> apply func to T to generate U
> apply func to U to generate W
> convert W to UnsafeRow
> append the new UnsafeRow to the original one
>
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