Github user aray commented on a diff in the pull request:
https://github.com/apache/spark/pull/7841#discussion_r44566886
--- Diff: sql/core/src/main/scala/org/apache/spark/sql/GroupedData.scala ---
@@ -273,6 +280,60 @@ class GroupedData protected[sql](
def sum(colNames: String*): DataFrame = {
aggregateNumericColumns(colNames : _*)(Sum)
}
+
+ /**
+ * (Scala-specific) Pivots a column of the current [[DataFrame]] and
preform the specified
+ * aggregation.
+ * {{{
+ * // Compute the sum of earnings for each year by course with each
course as a separate column
+ * df.groupBy($"year").pivot($"course", "dotNET",
"Java").agg(sum($"earnings"))
+ * // Or without specifying column values
+ * df.groupBy($"year").pivot($"course").agg(sum($"earnings"))
+ * }}}
--- End diff --
There is a note below in the description of the values parameter
>If values are not provided the method with do an immediate call to
.distinct() on the pivot column.
Do we need to duplicate/move that note to the method description?
Right now if there is too many distinct values we probably get OOM. Obvious
solve is to have some configurable maximum above which we give an error. Should
I try to add that now?
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