io.prestosql.sql.planner.iterative.rule.RemoveRedundantIdentityProjections 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.prestosql.sql.planner.iterative.rule;
import com.google.common.collect.ImmutableSet;
import io.prestosql.matching.Captures;
import io.prestosql.matching.Pattern;
import io.prestosql.sql.planner.iterative.Rule;
import io.prestosql.sql.planner.plan.ProjectNode;
import static io.prestosql.sql.planner.plan.Patterns.project;
/**
* Removes projection nodes that only perform non-renaming identity projections
*/
public class RemoveRedundantIdentityProjections
implements Rule
{
private static final Pattern PATTERN = project()
.matching(ProjectNode::isIdentity)
// only drop this projection if it does not constrain the outputs
// of its child
.matching(RemoveRedundantIdentityProjections::outputsSameAsSource);
private static boolean outputsSameAsSource(ProjectNode node)
{
return ImmutableSet.copyOf(node.getOutputSymbols()).equals(ImmutableSet.copyOf(node.getSource().getOutputSymbols()));
}
@Override
public Pattern getPattern()
{
return PATTERN;
}
@Override
public Result apply(ProjectNode project, Captures captures, Context context)
{
return Result.ofPlanNode(project.getSource());
}
}