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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.drill.exec.physical.impl.join;
import javax.inject.Named;
import org.apache.drill.exec.exception.SchemaChangeException;
import org.apache.drill.exec.ops.FragmentContext;
import org.apache.drill.exec.physical.config.MergeJoinPOP;
import org.apache.drill.exec.record.VectorContainer;
import org.eigenbase.rel.JoinRelType;
/**
* This join template uses a merge join to combine two ordered streams into a single larger batch. When joining
* single values on each side, the values can be copied to the outgoing batch immediately. The outgoing record batch
* should be sent as needed (e.g. schema change or outgoing batch full). When joining multiple values on one or
* both sides, two passes over the vectors will be made; one to construct the selection vector, and another to
* generate the outgoing batches once the duplicate value is no longer encountered.
*
* Given two tables ordered by 'col1':
*
* t1 t2
* --------------- ---------------
* | key | col2 | | key | col2 |
* --------------- ---------------
* | 1 | 'ab' | | 1 | 'AB' |
* | 2 | 'cd' | | 2 | 'CD' |
* | 2 | 'ef' | | 4 | 'EF' |
* | 4 | 'gh' | | 4 | 'GH' |
* | 4 | 'ij' | | 5 | 'IJ' |
* --------------- ---------------
*
* 'SELECT * FROM t1 INNER JOIN t2 on (t1.key == t2.key)' should generate the following:
*
* ---------------------------------
* | t1.key | t2.key | col1 | col2 |
* ---------------------------------
* | 1 | 1 | 'ab' | 'AB' |
* | 2 | 2 | 'cd' | 'CD' |
* | 2 | 2 | 'ef' | 'CD' |
* | 4 | 4 | 'gh' | 'EF' |
* | 4 | 4 | 'gh' | 'GH' |
* | 4 | 4 | 'ij' | 'EF' |
* | 4 | 4 | 'ij' | 'GH' |
* ---------------------------------
*
* In the simple match case, only one row from each table matches. Additional cases should be considered:
* - a left join key matches multiple right join keys
* - duplicate keys which may span multiple record batches (on the left and/or right side)
* - one or both incoming record batches change schemas
*
* In the case where a left join key matches multiple right join keys:
* - add a reference to all of the right table's matching values to the SV4.
*
* A RecordBatchData object should be used to hold onto all batches which have not been sent.
*
* JoinStatus:
* - all state related to the join operation is stored in the JoinStatus object.
* - this is required since code may be regenerated before completion of an outgoing record batch.
*/
public abstract class JoinTemplate implements JoinWorker {
@Override
public void setupJoin(FragmentContext context, JoinStatus status, VectorContainer outgoing) throws SchemaChangeException {
doSetup(context, status, outgoing);
}
/**
* Copy rows from the input record batches until the output record batch is full
* @param status State of the join operation (persists across multiple record batches/schema changes)
* @return true of join succeeded; false if the worker needs to be regenerated
*/
public final boolean doJoin(final JoinStatus status) {
while (true) {
// for each record
// validate input iterators (advancing to the next record batch if necessary)
if (!status.isRightPositionAllowed()) {
if (((MergeJoinPOP)status.outputBatch.getPopConfig()).getJoinType() == JoinRelType.LEFT) {
// we've hit the end of the right record batch; copy any remaining values from the left batch
while (status.isLeftPositionAllowed()) {
if (!doCopyLeft(status.getLeftPosition(), status.getOutPosition()))
return false;
status.incOutputPos();
status.advanceLeft();
}
}
return true;
}
if (!status.isLeftPositionAllowed())
return true;
int comparison = doCompare(status.getLeftPosition(), status.getRightPosition());
switch (comparison) {
case -1:
// left key < right key
if (((MergeJoinPOP)status.outputBatch.getPopConfig()).getJoinType() == JoinRelType.LEFT) {
if (!doCopyLeft(status.getLeftPosition(), status.getOutPosition()))
return false;
status.incOutputPos();
}
status.advanceLeft();
continue;
case 0:
// left key == right key
// check for repeating values on the left side
if (!status.isLeftRepeating() &&
status.isNextLeftPositionInCurrentBatch() &&
doCompareNextLeftKey(status.getLeftPosition()) == 0)
// subsequent record(s) in the left batch have the same key
status.notifyLeftRepeating();
else if (status.isLeftRepeating() &&
status.isNextLeftPositionInCurrentBatch() &&
doCompareNextLeftKey(status.getLeftPosition()) != 0)
// this record marks the end of repeated keys
status.notifyLeftStoppedRepeating();
boolean crossedBatchBoundaries = false;
int initialRightPosition = status.getRightPosition();
do {
// copy all equal right keys to the output record batch
if (!doCopyLeft(status.getLeftPosition(), status.getOutPosition()))
return false;
if (!doCopyRight(status.getRightPosition(), status.getOutPosition()))
return false;
status.incOutputPos();
// If the left key has duplicates and we're about to cross a boundary in the right batch, add the
// right table's record batch to the sv4 builder before calling next. These records will need to be
// copied again for each duplicate left key.
if (status.isLeftRepeating() && !status.isRightPositionInCurrentBatch()) {
status.outputBatch.addRightToBatchBuilder();
crossedBatchBoundaries = true;
}
status.advanceRight();
} while ((!status.isLeftRepeating() || status.isRightPositionInCurrentBatch()) && status.isRightPositionAllowed() && doCompare(status.getLeftPosition(), status.getRightPosition()) == 0);
if (status.getRightPosition() > initialRightPosition &&
(status.isLeftRepeating() || ! status.isNextLeftPositionInCurrentBatch()))
// more than one matching result from right table; reset position in case of subsequent left match
status.setRightPosition(initialRightPosition);
status.advanceLeft();
if (status.isLeftRepeating() && doCompareNextLeftKey(status.getLeftPosition()) != 0) {
// left no longer has duplicates. switch back to incoming batch mode
status.setDefaultAdvanceMode();
status.notifyLeftStoppedRepeating();
} else if (status.isLeftRepeating() && crossedBatchBoundaries) {
try {
// build the right batches and
status.outputBatch.batchBuilder.build();
status.setSV4AdvanceMode();
} catch (SchemaChangeException e) {
status.ok = false;
}
// return to indicate recompile in right-sv4 mode
return true;
}
continue;
case 1:
// left key > right key
status.advanceRight();
continue;
default:
throw new IllegalStateException();
}
}
}
// Generated Methods
public abstract void doSetup(@Named("context") FragmentContext context,
@Named("status") JoinStatus status,
@Named("outgoing") VectorContainer outgoing) throws SchemaChangeException;
/**
* Copy the data to the new record batch (if it fits).
*
* @param leftIndex position of batch (lower 16 bits) and record (upper 16 bits) in left SV4
* @param outIndex position of the output record batch
* @return Whether or not the data was copied.
*/
public abstract boolean doCopyLeft(@Named("leftIndex") int leftIndex, @Named("outIndex") int outIndex);
public abstract boolean doCopyRight(@Named("rightIndex") int rightIndex, @Named("outIndex") int outIndex);
/**
* Compare the values of the left and right join key to determine whether the left is less than, greater than
* or equal to the right.
*
* @param leftIndex
* @param rightIndex
* @return 0 if both keys are equal
* -1 if left is < right
* 1 if left is > right
*/
protected abstract int doCompare(@Named("leftIndex") int leftIndex,
@Named("rightIndex") int rightIndex);
/**
* Compare the current left key to the next left key, if it's within the batch.
* @return 0 if both keys are equal
* 1 if the keys are not equal
* -1 if there are no more keys in this batch
*/
protected abstract int doCompareNextLeftKey(@Named("leftIndex") int leftIndex);
}
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