GitHub user marmbrus opened a pull request:
https://github.com/apache/spark/pull/9359
[SPARK-11404] [SQL] Support for groupBy using column expressions
This PR adds a new method `groupBy(cols: Column*)` to `Dataset` that allows
users to group using column expressions instead of a lambda function. Since
the return type of these expressions is not known at compile time, we just set
the key type as a generic `Row`. If the user would like to work the key in a
type-safe way, they can call `grouped.asKey[Type]`, which is also added in this
PR.
```scala
val ds = Seq(("a", 10), ("a", 20), ("b", 1), ("b", 2), ("c", 1)).toDS()
val grouped = ds.groupBy($"_1").asKey[String]
val agged = grouped.mapGroups { case (g, iter) =>
Iterator((g, iter.map(_._2).sum))
}
agged.collect()
res0: Array(("a", 30), ("b", 3), ("c", 1))
```
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/marmbrus/spark columnGroupBy
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/9359.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #9359
----
commit 0b0e2f880518e2b4b2b5ea025bf76345c48775c2
Author: Michael Armbrust <[email protected]>
Date: 2015-10-29T15:22:03Z
[SPARK-11404] [SQL] Support for groupBy using column expressions
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