/**
* 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.tajo.engine.planner.physical;
import org.apache.tajo.worker.TaskAttemptContext;
import org.apache.tajo.catalog.Column;
import org.apache.tajo.engine.eval.EvalContext;
import org.apache.tajo.engine.eval.EvalNode;
import org.apache.tajo.engine.planner.PlannerUtil;
import org.apache.tajo.engine.planner.Projector;
import org.apache.tajo.engine.planner.logical.JoinNode;
import org.apache.tajo.engine.utils.SchemaUtil;
import org.apache.tajo.storage.FrameTuple;
import org.apache.tajo.storage.Tuple;
import org.apache.tajo.storage.VTuple;
import java.io.IOException;
import java.util.*;
public class HashJoinExec extends BinaryPhysicalExec {
// from logical plan
protected JoinNode plan;
protected EvalNode joinQual;
protected List<Column[]> joinKeyPairs;
// temporal tuples and states for nested loop join
protected boolean first = true;
protected FrameTuple frameTuple;
protected Tuple outTuple = null;
protected Map<Tuple, List<Tuple>> tupleSlots;
protected Iterator<Tuple> iterator = null;
protected EvalContext qualCtx;
protected Tuple leftTuple;
protected Tuple leftKeyTuple;
protected int [] leftKeyList;
protected int [] rightKeyList;
protected boolean finished = false;
protected boolean shouldGetLeftTuple = true;
// projection
protected final Projector projector;
protected final EvalContext [] evalContexts;
public HashJoinExec(TaskAttemptContext context, JoinNode plan, PhysicalExec outer,
PhysicalExec inner) {
super(context, SchemaUtil.merge(outer.getSchema(), inner.getSchema()),
plan.getOutSchema(), outer, inner);
this.plan = plan;
this.joinQual = plan.getJoinQual();
this.qualCtx = joinQual.newContext();
this.tupleSlots = new HashMap<Tuple, List<Tuple>>(10000);
this.joinKeyPairs = PlannerUtil.getJoinKeyPairs(joinQual,
outer.getSchema(), inner.getSchema());
leftKeyList = new int[joinKeyPairs.size()];
rightKeyList = new int[joinKeyPairs.size()];
for (int i = 0; i < joinKeyPairs.size(); i++) {
leftKeyList[i] = outer.getSchema().getColumnId(joinKeyPairs.get(i)[0].getQualifiedName());
}
for (int i = 0; i < joinKeyPairs.size(); i++) {
rightKeyList[i] = inner.getSchema().getColumnId(joinKeyPairs.get(i)[1].getQualifiedName());
}
// for projection
this.projector = new Projector(inSchema, outSchema, plan.getTargets());
this.evalContexts = projector.renew();
// for join
frameTuple = new FrameTuple();
outTuple = new VTuple(outSchema.getColumnNum());
leftKeyTuple = new VTuple(leftKeyList.length);
}
protected void getKeyLeftTuple(final Tuple outerTuple, Tuple keyTuple) {
for (int i = 0; i < leftKeyList.length; i++) {
keyTuple.put(i, outerTuple.get(leftKeyList[i]));
}
}
public Tuple next() throws IOException {
if (first) {
loadRightToHashTable();
}
Tuple rightTuple;
boolean found = false;
while(!finished) {
if (shouldGetLeftTuple) { // initially, it is true.
// getting new outer
leftTuple = leftChild.next(); // it comes from a disk
if (leftTuple == null) { // if no more tuples in left tuples on disk, a join is completed.
finished = true;
return null;
}
// getting corresponding right
getKeyLeftTuple(leftTuple, leftKeyTuple); // get a left key tuple
if (tupleSlots.containsKey(leftKeyTuple)) { // finds right tuples on in-memory hash table.
iterator = tupleSlots.get(leftKeyTuple).iterator();
shouldGetLeftTuple = false;
} else {
shouldGetLeftTuple = true;
continue;
}
}
// getting a next right tuple on in-memory hash table.
rightTuple = iterator.next();
frameTuple.set(leftTuple, rightTuple); // evaluate a join condition on both tuples
joinQual.eval(qualCtx, inSchema, frameTuple);
if (joinQual.terminate(qualCtx).asBool()) { // if both tuples are joinable
projector.eval(evalContexts, frameTuple);
projector.terminate(evalContexts, outTuple);
found = true;
}
if (!iterator.hasNext()) { // no more right tuples for this hash key
shouldGetLeftTuple = true;
}
if (found) {
break;
}
}
return outTuple;
}
protected void loadRightToHashTable() throws IOException {
Tuple tuple;
Tuple keyTuple;
while ((tuple = rightChild.next()) != null) {
keyTuple = new VTuple(joinKeyPairs.size());
List<Tuple> newValue;
for (int i = 0; i < rightKeyList.length; i++) {
keyTuple.put(i, tuple.get(rightKeyList[i]));
}
if (tupleSlots.containsKey(keyTuple)) {
newValue = tupleSlots.get(keyTuple);
newValue.add(tuple);
tupleSlots.put(keyTuple, newValue);
} else {
newValue = new ArrayList<Tuple>();
newValue.add(tuple);
tupleSlots.put(keyTuple, newValue);
}
}
first = false;
}
@Override
public void rescan() throws IOException {
super.rescan();
tupleSlots.clear();
first = true;
finished = false;
iterator = null;
shouldGetLeftTuple = true;
}
public void close() throws IOException {
tupleSlots.clear();
}
public JoinNode getPlan() {
return this.plan;
}
}