org.apache.hadoop.hive.ql.optimizer.physical.SamplingOptimizer Maven / Gradle / Ivy
/**
* Copyright 2010 The Apache Software Foundation
*
* 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.hadoop.hive.ql.optimizer.physical;
import org.apache.hadoop.hive.ql.exec.Operator;
import org.apache.hadoop.hive.ql.exec.OperatorUtils;
import org.apache.hadoop.hive.ql.exec.ReduceSinkOperator;
import org.apache.hadoop.hive.ql.exec.TableScanOperator;
import org.apache.hadoop.hive.ql.exec.Task;
import org.apache.hadoop.hive.ql.exec.mr.MapRedTask;
import org.apache.hadoop.hive.ql.parse.SemanticException;
import org.apache.hadoop.hive.ql.plan.MapWork;
import org.apache.hadoop.hive.ql.plan.MapredWork;
import org.apache.hadoop.hive.ql.plan.ReduceWork;
/**
* Mark final MapredWork for ORDER BY to use sampling and set number of reduce task as -1
*/
public class SamplingOptimizer implements PhysicalPlanResolver {
public PhysicalContext resolve(PhysicalContext pctx) throws SemanticException {
for (Task task : pctx.getRootTasks()) {
if (!(task instanceof MapRedTask) || !((MapRedTask)task).getWork().isFinalMapRed()) {
continue; // this could be replaced by bucketing on RS + bucketed fetcher for next MR
}
MapredWork mrWork = ((MapRedTask) task).getWork();
MapWork mapWork = mrWork.getMapWork();
ReduceWork reduceWork = mrWork.getReduceWork();
if (reduceWork == null || reduceWork.getNumReduceTasks() != 1
|| mapWork.getAliasToWork().size() != 1 || mapWork.getSamplingType() > 0
|| reduceWork.getReducer() == null) {
continue;
}
Operator operator = mapWork.getAliasToWork().values().iterator().next();
if (!(operator instanceof TableScanOperator)) {
continue;
}
ReduceSinkOperator child =
OperatorUtils.findSingleOperator(operator, ReduceSinkOperator.class);
if (child == null ||
child.getConf().getNumReducers() != 1 || !child.getConf().getPartitionCols().isEmpty()) {
continue;
}
child.getConf().setNumReducers(-1);
reduceWork.setNumReduceTasks(-1);
mapWork.setSamplingType(MapWork.SAMPLING_ON_START);
}
return pctx;
}
}