b86f2cab67
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)) ``` Author: Michael Armbrust <michael@databricks.com> Closes #9359 from marmbrus/columnGroupBy and squashes the following commits: bbcb03b [Michael Armbrust] Update DatasetSuite.scala 8fd2908 [Michael Armbrust] Update DatasetSuite.scala 0b0e2f8 [Michael Armbrust] [SPARK-11404] [SQL] Support for groupBy using column expressions |
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