/**
* 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.calcite.rules;
import org.apache.calcite.plan.RelOptRule;
import org.apache.calcite.plan.RelOptRuleCall;
import org.apache.calcite.rel.RelNode;
import org.apache.calcite.rel.core.Join;
import org.apache.calcite.rel.core.Project;
import org.apache.calcite.rel.rules.JoinCommuteRule;
import org.apache.calcite.util.Permutation;
import org.apache.hadoop.hive.ql.optimizer.calcite.reloperators.HiveJoin;
import org.apache.hadoop.hive.ql.optimizer.calcite.reloperators.HiveProject;
/**
* Planner rule that permutes the inputs of a Join, if it has a Project on top
* that simply swaps the fields of both inputs.
*/
public class HiveJoinCommuteRule extends RelOptRule {
public static final HiveJoinCommuteRule INSTANCE = new HiveJoinCommuteRule(
HiveProject.class, HiveJoin.class);
public HiveJoinCommuteRule(Class<? extends Project> projClazz,
Class<? extends Join> joinClazz) {
super(operand(projClazz,
operand(joinClazz, any())));
}
public void onMatch(final RelOptRuleCall call) {
Project topProject = call.rel(0);
Join join = call.rel(1);
// 1. We check if it is a permutation project. If it is
// not, or this is the identity, the rule will do nothing
final Permutation topPermutation = topProject.getPermutation();
if (topPermutation == null) {
return;
}
if (topPermutation.isIdentity()) {
return;
}
// 2. We swap the join
final RelNode swapped = JoinCommuteRule.swap(join,true);
if (swapped == null) {
return;
}
// 3. The result should have a project on top, otherwise we
// bail out.
if (swapped instanceof Join) {
return;
}
// 4. We check if it is a permutation project. If it is
// not, or this is the identity, the rule will do nothing
final Project bottomProject = (Project) swapped;
final Permutation bottomPermutation = bottomProject.getPermutation();
if (bottomPermutation == null) {
return;
}
if (bottomPermutation.isIdentity()) {
return;
}
// 5. If the product of the topPermutation and bottomPermutation yields
// the identity, then we can swap the join and remove the project on
// top.
final Permutation product = topPermutation.product(bottomPermutation);
if (!product.isIdentity()) {
return;
}
// 6. Return the new join as a replacement
final Join swappedJoin = (Join) bottomProject.getInput(0);
call.transformTo(swappedJoin);
}
}