Github user tdas commented on a diff in the pull request: https://github.com/apache/spark/pull/16758#discussion_r98786650 --- Diff: sql/core/src/main/scala/org/apache/spark/sql/State.scala --- @@ -0,0 +1,101 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one or more + * contributor license agreements. See the NOTICE file distributed with + * this work for additional information regarding copyright ownership. + * The ASF licenses this file to You under the Apache License, Version 2.0 + * (the "License"); you may not use this file except in compliance with + * the License. You may obtain a copy of the License at + * + * http://www.apache.org/licenses/LICENSE-2.0 + * + * Unless required by applicable law or agreed to in writing, software + * distributed under the License is distributed on an "AS IS" BASIS, + * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. + * See the License for the specific language governing permissions and + * limitations under the License. + */ + +package org.apache.spark.sql + +import org.apache.spark.annotation.{Experimental, InterfaceStability} +import org.apache.spark.sql.catalyst.plans.logical.LogicalState + +/** + * :: Experimental :: + * + * Wrapper class for interacting with state data in `mapGroupsWithState` and + * `flatMapGroupsWithState` operations on + * [[org.apache.spark.sql.KeyValueGroupedDataset KeyValueGroupedDataset]]. + * + * @note Operations on state are not threadsafe. + * + * Scala example of using `State`: + * {{{ + * // A mapping function that maintains an integer state for string keys and returns a string. + * def mappingFunction(key: String, value: Iterable[Int], state: State[Int]): Option[String] = { + * // Check if state exists + * if (state.exists) { + * val existingState = state.get // Get the existing state + * val shouldRemove = ... // Decide whether to remove the state + * if (shouldRemove) { + * state.remove() // Remove the state + * } else { + * val newState = ... + * state.update(newState) // Set the new state + * } + * } else { + * val initialState = ... + * state.update(initialState) // Set the initial state + * } + * ... // return something + * } + * + * }}} + * + * Java example of using `State`: + * {{{ + * // A mapping function that maintains an integer state for string keys and returns a string. + * Function3<String, Iterable<Integer>, State<Integer>, String> mappingFunction = + * new Function3<String, Iterable<Integer>, State<Integer>, String>() { + * + * @Override + * public String call(String key, Optional<Integer> value, State<Integer> state) { + * if (state.exists()) { + * int existingState = state.get(); // Get the existing state + * boolean shouldRemove = ...; // Decide whether to remove the state + * if (shouldRemove) { + * state.remove(); // Remove the state + * } else { + * int newState = ...; + * state.update(newState); // Set the new state + * } + * } else { + * int initialState = ...; // Set the initial state + * state.update(initialState); + * } + * ... // return something + * } + * }; + * }}} + * + * @tparam S Type of the state + * @since 2.1.1 + */ +@Experimental +@InterfaceStability.Evolving +trait State[S] extends LogicalState[S] { + + def exists: Boolean + + def get(): S + + def update(newState: S): Unit + + def remove(): Unit --- End diff -- Will do.
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