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/**
* 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 java.io.Serializable;
import java.util.ArrayList;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Stack;
import org.apache.hadoop.hive.ql.exec.CommonJoinOperator;
import org.apache.hadoop.hive.ql.exec.ConditionalTask;
import org.apache.hadoop.hive.ql.exec.Task;
import org.apache.hadoop.hive.ql.lib.DefaultGraphWalker;
import org.apache.hadoop.hive.ql.lib.DefaultRuleDispatcher;
import org.apache.hadoop.hive.ql.lib.Dispatcher;
import org.apache.hadoop.hive.ql.lib.GraphWalker;
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.lib.Rule;
import org.apache.hadoop.hive.ql.lib.RuleRegExp;
import org.apache.hadoop.hive.ql.parse.ParseContext;
import org.apache.hadoop.hive.ql.parse.SemanticException;
import org.apache.hadoop.hive.ql.plan.MapredWork;
/**
* An implementation of PhysicalPlanResolver. It iterator each task with a rule
* dispatcher for its reducer operator tree, for task with join op in reducer,
* it will try to add a conditional task associated a list of skew join tasks.
*/
public class SkewJoinResolver implements PhysicalPlanResolver {
@Override
public PhysicalContext resolve(PhysicalContext pctx) throws SemanticException {
Dispatcher disp = new SkewJoinTaskDispatcher(pctx);
GraphWalker ogw = new DefaultGraphWalker(disp);
ArrayList topNodes = new ArrayList();
topNodes.addAll(pctx.rootTasks);
ogw.startWalking(topNodes, null);
return pctx;
}
/**
* Iterator a task with a rule dispatcher for its reducer operator tree.
*/
class SkewJoinTaskDispatcher implements Dispatcher {
private PhysicalContext physicalContext;
public SkewJoinTaskDispatcher(PhysicalContext context) {
super();
physicalContext = context;
}
@Override
public Object dispatch(Node nd, Stack stack, Object... nodeOutputs)
throws SemanticException {
Task extends Serializable> task = (Task extends Serializable>) nd;
if (!task.isMapRedTask() || task instanceof ConditionalTask
|| ((MapredWork) task.getWork()).getReducer() == null) {
return null;
}
SkewJoinProcCtx skewJoinProcContext = new SkewJoinProcCtx(task,
physicalContext.getParseContext());
Map opRules = new LinkedHashMap();
opRules.put(new RuleRegExp("R1",
CommonJoinOperator.getOperatorName() + "%"),
SkewJoinProcFactory.getJoinProc());
// The dispatcher fires the processor corresponding to the closest
// matching rule and passes the context along
Dispatcher disp = new DefaultRuleDispatcher(SkewJoinProcFactory
.getDefaultProc(), opRules, skewJoinProcContext);
GraphWalker ogw = new DefaultGraphWalker(disp);
// iterator the reducer operator tree
ArrayList topNodes = new ArrayList();
topNodes.add(((MapredWork) task.getWork()).getReducer());
ogw.startWalking(topNodes, null);
return null;
}
public PhysicalContext getPhysicalContext() {
return physicalContext;
}
public void setPhysicalContext(PhysicalContext physicalContext) {
this.physicalContext = physicalContext;
}
}
/**
* A container of current task and parse context.
*/
public static class SkewJoinProcCtx implements NodeProcessorCtx {
private Task extends Serializable> currentTask;
private ParseContext parseCtx;
public SkewJoinProcCtx(Task extends Serializable> task,
ParseContext parseCtx) {
currentTask = task;
this.parseCtx = parseCtx;
}
public Task extends Serializable> getCurrentTask() {
return currentTask;
}
public void setCurrentTask(Task extends Serializable> currentTask) {
this.currentTask = currentTask;
}
public ParseContext getParseCtx() {
return parseCtx;
}
public void setParseCtx(ParseContext parseCtx) {
this.parseCtx = parseCtx;
}
}
}
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