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ASF GitHub Bot commented on FLINK-2991: --------------------------------------- Github user tillrohrmann commented on a diff in the pull request: https://github.com/apache/flink/pull/1605#discussion_r52445522 --- Diff: flink-core/src/main/java/org/apache/flink/api/common/state/FoldingStateDescriptor.java --- @@ -0,0 +1,108 @@ +/* + * 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.flink.api.common.state; + +import org.apache.flink.api.common.functions.FoldFunction; +import org.apache.flink.api.common.functions.RichFunction; +import org.apache.flink.api.common.typeinfo.TypeInformation; +import org.apache.flink.api.common.typeutils.TypeSerializer; + +import static java.util.Objects.requireNonNull; + +/** + * {@link StateDescriptor} for {@link ReducingState}. This can be used to create partitioned + * folding state. + * + * @param <T> Type of the values folded int othe state + * @param <ACC> Type of the value in the state + */ +public class FoldingStateDescriptor<T, ACC> extends StateDescriptor<FoldingState<T, ACC>, ACC> { + private static final long serialVersionUID = 1L; + + + private final FoldFunction<T, ACC> foldFunction; + + /** + * Creates a new {@code FoldingStateDescriptor} with the given name, type, and initial value. + * + * <p>If this constructor fails (because it is not possible to describe the type via a class), + * consider using the {@link #FoldingStateDescriptor(String, ACC, FoldFunction, TypeInformation)} constructor. + * + * @param name The (unique) name for the state. + * @param initialValue The initial value of the fold. + * @param foldFunction The {@code FoldFunction} used to aggregate the state. + * @param typeClass The type of the values in the state. + */ + public FoldingStateDescriptor(String name, ACC initialValue, FoldFunction<T, ACC> foldFunction, Class<ACC> typeClass) { + super(name, typeClass, initialValue); + this.foldFunction = requireNonNull(foldFunction); + + if (foldFunction instanceof RichFunction) { + throw new UnsupportedOperationException("FoldFunction of FoldingState can not be a RichFunction."); + } + } + + /** + * Creates a new {@code ReducingStateDescriptor} with the given name and default value. --- End diff -- FoldingStateDescriptor > Extend Window Operators to Allow Efficient Fold Operation > --------------------------------------------------------- > > Key: FLINK-2991 > URL: https://issues.apache.org/jira/browse/FLINK-2991 > Project: Flink > Issue Type: Improvement > Components: Streaming > Reporter: Aljoscha Krettek > Assignee: Aljoscha Krettek > > Right now, a window fold is implemented as a WindowFunction that gets all the > elements as input. No pre-aggregation is performed. The window operator > should be extended to also allow the fold to also be pre-aggregated. > This requires changing the signature of the {{WindowBuffer}} so that it can > emit a type other than the input type. -- This message was sent by Atlassian JIRA (v6.3.4#6332)