| /** |
| * 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.apex.malhar.lib.window; |
| |
| import org.apache.hadoop.classification.InterfaceStability; |
| |
| /** |
| * This interface is for the processing part of the WindowedOperator. |
| * We can assume that all stateful processing of the WindowedOperator is a form of accumulation. |
| * |
| * In most cases, AccumT is the same as OutputT. But in some cases, the accumulated type and the output type may be |
| * different. For example, if we are doing the AVERAGE of doubles, InputT will be double, and we need the SUM and the |
| * COUNT stored as type AccumT, and AccumT will be a pair of double and long, in which double is the sum of the inputs, |
| * and long is the number of inputs. OutputT will be double, because it represents the average of the inputs. |
| * |
| * @since 3.5.0 |
| */ |
| @InterfaceStability.Evolving |
| public interface Accumulation<InputT, AccumT, OutputT> |
| { |
| /** |
| * Returns the default accumulated value when nothing has been accumulated |
| * |
| * @return |
| */ |
| AccumT defaultAccumulatedValue(); |
| |
| /** |
| * Accumulates the input to the accumulated value |
| * |
| * @param accumulatedValue |
| * @param input |
| * @return |
| */ |
| AccumT accumulate(AccumT accumulatedValue, InputT input); |
| |
| /** |
| * Merges two accumulated value into one |
| * |
| * @param accumulatedValue1 |
| * @param accumulatedValue2 |
| * @return |
| */ |
| AccumT merge(AccumT accumulatedValue1, AccumT accumulatedValue2); |
| |
| /** |
| * Gets the output of the accumulated value. This is used for generating the data for triggers |
| * |
| * @param accumulatedValue |
| * @return |
| */ |
| OutputT getOutput(AccumT accumulatedValue); |
| |
| /** |
| * Gets the retraction of the value. This is used for retracting previous panes in |
| * ACCUMULATING_AND_RETRACTING accumulation mode |
| * |
| * @param value |
| * @return |
| */ |
| OutputT getRetraction(OutputT value); |
| } |