tdas commented on a change in pull request #33093:
URL: https://github.com/apache/spark/pull/33093#discussion_r662282624



##########
File path: 
sql/core/src/main/scala/org/apache/spark/sql/KeyValueGroupedDataset.scala
##########
@@ -280,6 +280,51 @@ class KeyValueGroupedDataset[K, V] private[sql](
         child = logicalPlan))
   }
 
+  /**
+   * (Scala-specific)
+   * Applies the given function to each group of data, while maintaining a 
user-defined per-group
+   * state. The result Dataset will represent the objects returned by the 
function.
+   * For a static batch Dataset, the function will be invoked once per group. 
For a streaming
+   * Dataset, the function will be invoked for each group repeatedly in every 
trigger, and
+   * updates to each group's state will be saved across invocations.
+   * See [[org.apache.spark.sql.streaming.GroupState]] for more details.
+   *
+   * @tparam S The type of the user-defined state. Must be encodable to Spark 
SQL types.
+   * @tparam U The type of the output objects. Must be encodable to Spark SQL 
types.
+   * @param func Function to be called on every group.
+   * @param timeoutConf Timeout Conf, see GroupStateTimeout for more details
+   * @param initialState The user provided state that will be initialized when 
the first batch
+   *                     of data is processed in the streaming query. The user 
defined function
+   *                     will be called on the state data even if there are no 
other values in
+   *                     the group. To convert a Dataset ds of type 
Dataset[(K, S)] to a

Review comment:
       ```
   To covert a Dataset `ds` of type  of type `Dataset[(K, S)]` .... to a 
`KeyValueGroupedDataset[K, S]`
   ```
   change in other places as well 




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