/**
* 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;
import java.util.Stack;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.hive.conf.HiveConf;
import org.apache.hadoop.hive.ql.exec.Operator;
import org.apache.hadoop.hive.ql.exec.ReduceSinkOperator;
import org.apache.hadoop.hive.ql.exec.Utilities;
import org.apache.hadoop.hive.ql.lib.Node;
import org.apache.hadoop.hive.ql.lib.NodeProcessor;
import org.apache.hadoop.hive.ql.lib.NodeProcessorCtx;
import org.apache.hadoop.hive.ql.parse.OptimizeTezProcContext;
import org.apache.hadoop.hive.ql.parse.SemanticException;
import org.apache.hadoop.hive.ql.plan.OperatorDesc;
import org.apache.hadoop.hive.ql.plan.ReduceSinkDesc;
/**
* SetReducerParallelism determines how many reducers should
* be run for a given reduce sink.
*/
public class SetReducerParallelism implements NodeProcessor {
static final private Log LOG = LogFactory.getLog(SetReducerParallelism.class.getName());
@SuppressWarnings("unchecked")
@Override
public Object process(Node nd, Stack<Node> stack,
NodeProcessorCtx procContext, Object... nodeOutputs)
throws SemanticException {
OptimizeTezProcContext context = (OptimizeTezProcContext) procContext;
ReduceSinkOperator sink = (ReduceSinkOperator) nd;
ReduceSinkDesc desc = sink.getConf();
long bytesPerReducer = context.conf.getLongVar(HiveConf.ConfVars.BYTESPERREDUCER);
int maxReducers = context.conf.getIntVar(HiveConf.ConfVars.MAXREDUCERS);
int constantReducers = context.conf.getIntVar(HiveConf.ConfVars.HADOOPNUMREDUCERS);
if (context.visitedReduceSinks.contains(sink)) {
// skip walking the children
LOG.debug("Already processed reduce sink: " + sink.getName());
return true;
}
context.visitedReduceSinks.add(sink);
if (desc.getNumReducers() <= 0) {
if (constantReducers > 0) {
LOG.info("Parallelism for reduce sink "+sink+" set by user to "+constantReducers);
desc.setNumReducers(constantReducers);
} else {
long numberOfBytes = 0;
// we need to add up all the estimates from the siblings of this reduce sink
for (Operator<? extends OperatorDesc> sibling:
sink.getChildOperators().get(0).getParentOperators()) {
if (sibling.getStatistics() != null) {
numberOfBytes += sibling.getStatistics().getDataSize();
} else {
LOG.warn("No stats available from: "+sibling);
}
}
int numReducers = Utilities.estimateReducers(numberOfBytes, bytesPerReducer,
maxReducers, false);
LOG.info("Set parallelism for reduce sink "+sink+" to: "+numReducers);
desc.setNumReducers(numReducers);
}
} else {
LOG.info("Number of reducers determined to be: "+desc.getNumReducers());
}
return false;
}
}