Github user zsxwing commented on a diff in the pull request:
https://github.com/apache/spark/pull/10224#discussion_r47173816
--- Diff:
streaming/src/main/scala/org/apache/spark/streaming/StateSpec.scala ---
@@ -91,115 +105,125 @@ sealed abstract class StateSpec[KeyType, ValueType,
StateType, EmittedType] exte
/**
* :: Experimental ::
* Builder object for creating instances of
[[org.apache.spark.streaming.StateSpec StateSpec]]
- * that is used for specifying the parameters of the DStream
transformation `trackStateByKey`
+ * that is used for specifying the parameters of the DStream
transformation `mapWithState`
* that is used for specifying the parameters of the DStream transformation
- * `trackStateByKey` operation of a
+ * `mapWithState` operation of a
* [[org.apache.spark.streaming.dstream.PairDStreamFunctions pair
DStream]] (Scala) or a
* [[org.apache.spark.streaming.api.java.JavaPairDStream JavaPairDStream]]
(Java).
*
* 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 emittedRecordDStream =
keyValueDStream.trackStateByKey[StateType, EmittedDataType](
- * StateSpec.function(trackingFunction).numPartitions(10))
+ * val spec = StateSpec.function(mappingFunction).numPartitions(10)
+ *
+ * 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 `Integer` now
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