Github user zsxwing commented on a diff in the pull request:
https://github.com/apache/spark/pull/10224#discussion_r47173853
--- Diff:
streaming/src/main/scala/org/apache/spark/streaming/StateSpec.scala ---
@@ -37,50 +37,64 @@ import org.apache.spark.{HashPartitioner, Partitioner}
*
* Example in Scala:
* {{{
- * def trackingFunction(data: Option[ValueType], wrappedState:
State[StateType]): EmittedType = {
- * ...
+ * // A mapping function that maintains an integer state and return a
String
+ * def mappingFunction(key: String, value: Option[Int], state:
State[Int]): Option[String] = {
+ * // Use state.exists(), state.get(), state.update() and
state.remove()
+ * // to manage state, and return the necessary string
* }
*
- * val spec = StateSpec.function(trackingFunction).numPartitions(10)
+ * val spec = StateSpec.function(mappingFunction).numPartitions(10)
*
- * val emittedRecordDStream =
keyValueDStream.trackStateByKey[StateType, EmittedDataType](spec)
+ * val mapWithStateDStream = keyValueDStream.mapWithState[StateType,
MappedType](spec)
* }}}
*
* Example in Java:
* {{{
- * StateSpec<KeyType, ValueType, StateType, EmittedDataType> spec =
- * StateSpec.<KeyType, ValueType, StateType,
EmittedDataType>function(trackingFunction)
- * .numPartition(10);
+ * // A mapping function that maintains an integer state and return a
string
+ * Function3<String, Optional<Integer>, State<Integer>, String>
mappingFunction =
+ * new Function3<String, Optional<Integer>, State<Integer>,
String>() {
+ * @Override
+ * public Optional<String> call(Optional<Integer> value,
State<Integer> state) {
+ * // Use state.exists(), state.get(), state.update() and
state.remove()
+ * // to manage state, and return the necessary string
+ * }
+ * };
*
- * JavaTrackStateDStream<KeyType, ValueType, StateType, EmittedType>
emittedRecordDStream =
- * javaPairDStream.<StateType, EmittedDataType>trackStateByKey(spec);
+ * JavaMapWithStateDStream<Integer, Integer, Integer, String>
mapWithStateDStream =
--- End diff --
nit: the key type is `String`
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