io.trino.sql.planner.iterative.rule.RemoveRedundantLimit 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 io.trino.matching.Captures;
import io.trino.matching.Pattern;
import io.trino.sql.planner.iterative.Rule;
import io.trino.sql.planner.plan.LimitNode;
import io.trino.sql.planner.plan.ValuesNode;
import static io.trino.sql.planner.optimizations.QueryCardinalityUtil.isAtMost;
import static io.trino.sql.planner.plan.Patterns.limit;
/**
* Remove Limit node when the subplan is guaranteed to produce fewer rows than the limit and
* replace the plan with empty values if the limit count is 0.
*/
public class RemoveRedundantLimit
implements Rule
{
// Applies to both LimitNode with ties and LimitNode without ties.
private static final Pattern PATTERN = limit();
@Override
public Pattern getPattern()
{
return PATTERN;
}
@Override
public Result apply(LimitNode limit, Captures captures, Context context)
{
if (limit.getCount() == 0) {
return Result.ofPlanNode(new ValuesNode(limit.getId(), limit.getOutputSymbols(), ImmutableList.of()));
}
if (isAtMost(limit.getSource(), context.getLookup(), limit.getCount())) {
return Result.ofPlanNode(limit.getSource());
}
return Result.empty();
}
}