io.trino.sql.planner.iterative.rule.RemoveEmptyMergeWriterRuleSet Maven / Gradle / Ivy

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/*
 * 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.ImmutableSet;
import io.trino.matching.Captures;
import io.trino.matching.Pattern;
import io.trino.sql.ir.Constant;
import io.trino.sql.ir.Row;
import io.trino.sql.planner.iterative.Rule;
import io.trino.sql.planner.plan.TableFinishNode;
import io.trino.sql.planner.plan.ValuesNode;

import java.util.Set;

import static io.trino.spi.type.BigintType.BIGINT;
import static io.trino.sql.planner.plan.Patterns.emptyValues;
import static io.trino.sql.planner.plan.Patterns.exchange;
import static io.trino.sql.planner.plan.Patterns.mergeWriter;
import static io.trino.sql.planner.plan.Patterns.project;
import static io.trino.sql.planner.plan.Patterns.source;
import static io.trino.sql.planner.plan.Patterns.tableFinish;
import static java.util.Objects.requireNonNull;

/**
 * If the predicate for a mergeWriter is optimized to false, the target table scan
 * of the mergeWriter will be replaced with an empty values node. This type of
 * plan cannot be executed and is meaningless anyway, so we replace the
 * entire thing with a values node.
 * 
 * Transforms
 * 
 *  - TableFinish
 *    - Exchange (optional)
 *      - MergeWriter
 *        - Exchange
 *          - Project
 *            - empty Values
 * 
 * into
 *  *  - Values (0)
 * 
 */
public final class RemoveEmptyMergeWriterRuleSet
{
    private RemoveEmptyMergeWriterRuleSet() {}

    public static Set> rules()
    {
        return ImmutableSet.of(
                removeEmptyMergeWriterRule(),
                removeEmptyMergeWriterWithExchangeRule());
    }

    static Rule removeEmptyMergeWriterRule()
    {
        return new RemoveEmptyMergeWriter(tableFinish()
                .with(source().matching(mergeWriter()
                        .with(source().matching(exchange()
                                .with(source().matching(project()
                                        .with(source().matching(emptyValues())))))))));
    }

    static Rule removeEmptyMergeWriterWithExchangeRule()
    {
        return new RemoveEmptyMergeWriter(tableFinish()
                .with(source().matching(exchange()
                        .with(source().matching(mergeWriter()
                                .with(source().matching(exchange()
                                        .with(source().matching(project()
                                                .with(source().matching(emptyValues())))))))))));
    }

    private static final class RemoveEmptyMergeWriter
            implements Rule
    {
        private final Pattern pattern;

        private RemoveEmptyMergeWriter(Pattern pattern)
        {
            this.pattern = requireNonNull(pattern, "pattern is null");
        }

        @Override
        public Pattern getPattern()
        {
            return pattern;
        }

        @Override
        public Result apply(TableFinishNode node, Captures captures, Context context)
        {
            return Result.ofPlanNode(
                    new ValuesNode(
                            node.getId(),
                            node.getOutputSymbols(),
                            ImmutableList.of(new Row(ImmutableList.of(new Constant(BIGINT, 0L))))));
        }
    }
}