zhengruifeng opened a new pull request #29185:
URL: https://github.com/apache/spark/pull/29185
### What changes were proposed in this pull request?
avoid unnecessary shuffle if possible
### Why are the changes needed?
In `combineByKeyWithClassTag`, there is a check to avoid unnecessary shuffle
if possible:
```scala
if (self.partitioner == Some(partitioner)) {
self.mapPartitions(iter => {
val context = TaskContext.get()
new InterruptibleIterator(context, aggregator.combineValuesByKey(iter,
context))
}, preservesPartitioning = true)
} else {
new ShuffledRDD[K, V, C](self, partitioner)
.setSerializer(serializer)
.setAggregator(aggregator)
.setMapSideCombine(mapSideCombine)
}
```
`repartitionAndSortWithinPartitions` should also avoid unnecessary shuffle.
### Does this PR introduce _any_ user-facing change?
No
### How was this patch tested?
added testsuites and existing testsuites
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