io.trino.sql.planner.iterative.rule.PruneUnionColumns Maven / Gradle / Ivy
/*
* Licensed 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 io.trino.sql.planner.iterative.rule;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.ImmutableListMultimap;
import io.trino.sql.planner.Symbol;
import io.trino.sql.planner.plan.PlanNode;
import io.trino.sql.planner.plan.UnionNode;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import static com.google.common.collect.ImmutableListMultimap.toImmutableListMultimap;
import static io.trino.sql.planner.plan.Patterns.union;
/**
* Transforms
*
* - Project (a)
* - Union
* output mappings: {a->c, a->e, b->d, b->f}
* - Source (c, d)
* - Source (e, f)
*
* into:
*
* - Project (a)
* - Union
* output mappings: {a->c, a->e}
* - Source (c, d)
* - Source (e, f)
*
* Note: as a result of this rule, the UnionNode's sources
* are eligible for pruning outputs. This is accomplished
* by PruneUnionSourceColumns rule.
*/
public class PruneUnionColumns
extends ProjectOffPushDownRule
{
public PruneUnionColumns()
{
super(union());
}
@Override
protected Optional pushDownProjectOff(Context context, UnionNode unionNode, Set referencedOutputs)
{
ImmutableListMultimap prunedOutputMappings = unionNode.getSymbolMapping().entries().stream()
.filter(entry -> referencedOutputs.contains(entry.getKey()))
.collect(toImmutableListMultimap(Map.Entry::getKey, Map.Entry::getValue));
return Optional.of(
new UnionNode(
unionNode.getId(),
unionNode.getSources(),
prunedOutputMappings,
ImmutableList.copyOf(prunedOutputMappings.keySet())));
}
}