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Merge pull request #12227 from cdapio/feature_release/CDAP-16856-mr-a…
…gg-impl CDAP-16856 mapreduce impl
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...cdap-etl/cdap-etl-core/src/main/java/io/cdap/cdap/etl/common/plugin/AggregatorBridge.java
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| /* | ||
| * Copyright © 2020 Cask Data, Inc. | ||
| * | ||
| * Licensed 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. | ||
| */ | ||
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| package io.cdap.cdap.etl.common.plugin; | ||
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| import io.cdap.cdap.etl.api.Emitter; | ||
| import io.cdap.cdap.etl.api.PipelineConfigurer; | ||
| import io.cdap.cdap.etl.api.batch.BatchAggregator; | ||
| import io.cdap.cdap.etl.api.batch.BatchAggregatorContext; | ||
| import io.cdap.cdap.etl.api.batch.BatchReducibleAggregator; | ||
| import io.cdap.cdap.etl.api.batch.BatchRuntimeContext; | ||
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| import java.util.Iterator; | ||
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| /** | ||
| * An implementation of {@link BatchAggregator} using a {@link BatchReducibleAggregator}. | ||
| * | ||
| * @param <GROUP_KEY> Type of group key | ||
| * @param <GROUP_VALUE> Type of values to group | ||
| * @param <AGG_VALUE> Type of agg values to group | ||
| * @param <OUT> Type of output object | ||
| */ | ||
| public class AggregatorBridge<GROUP_KEY, GROUP_VALUE, AGG_VALUE, OUT> | ||
| extends BatchAggregator<GROUP_KEY, GROUP_VALUE, OUT> { | ||
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| private final BatchReducibleAggregator<GROUP_KEY, GROUP_VALUE, AGG_VALUE, OUT> aggregator; | ||
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| public AggregatorBridge(BatchReducibleAggregator<GROUP_KEY, GROUP_VALUE, AGG_VALUE, OUT> aggregator) { | ||
| this.aggregator = aggregator; | ||
| } | ||
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| @Override | ||
| public void configurePipeline(PipelineConfigurer pipelineConfigurer) { | ||
| aggregator.configurePipeline(pipelineConfigurer); | ||
| } | ||
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| @Override | ||
| public void prepareRun(BatchAggregatorContext context) throws Exception { | ||
| aggregator.prepareRun(context); | ||
| } | ||
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| @Override | ||
| public void initialize(BatchRuntimeContext context) throws Exception { | ||
| aggregator.initialize(context); | ||
| } | ||
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| @Override | ||
| public void destroy() { | ||
| aggregator.destroy(); | ||
| } | ||
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| @Override | ||
| public void onRunFinish(boolean succeeded, BatchAggregatorContext context) { | ||
| aggregator.onRunFinish(succeeded, context); | ||
| } | ||
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| @Override | ||
| public void groupBy(GROUP_VALUE groupValue, Emitter<GROUP_KEY> emitter) throws Exception { | ||
| aggregator.groupBy(groupValue, emitter); | ||
| } | ||
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| @Override | ||
| public void aggregate(GROUP_KEY groupKey, Iterator<GROUP_VALUE> groupValues, Emitter<OUT> emitter) throws Exception { | ||
| // this condition should not happen, since the group key is generated with the groupBy with existing input, so the | ||
| // iterator will at least contain that value | ||
| if (!groupValues.hasNext()) { | ||
| return; | ||
| } | ||
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| // create first agg value | ||
| AGG_VALUE aggVal = aggregator.initializeAggregateValue(groupValues.next()); | ||
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| // loop the iterator to combine the values, here the mergePartitions will not be used since the iterator already | ||
| // has all the values with the key from all partitions | ||
| while (groupValues.hasNext()) { | ||
| aggVal = aggregator.mergeValues(aggVal, groupValues.next()); | ||
| } | ||
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| // after we get the final aggVal, we can finalize the result | ||
| aggregator.finalize(groupKey, aggVal, emitter); | ||
| } | ||
| } |