io.trino.sql.planner.iterative.rule.RemoveRedundantExists 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 io.trino.matching.Captures;
import io.trino.matching.Pattern;
import io.trino.sql.ir.Expression;
import io.trino.sql.planner.Symbol;
import io.trino.sql.planner.iterative.Rule;
import io.trino.sql.planner.optimizations.Cardinality;
import io.trino.sql.planner.plan.ApplyNode;
import io.trino.sql.planner.plan.Assignments;
import io.trino.sql.planner.plan.ProjectNode;

import static io.trino.sql.ir.Booleans.FALSE;
import static io.trino.sql.ir.Booleans.TRUE;
import static io.trino.sql.planner.optimizations.QueryCardinalityUtil.extractCardinality;
import static io.trino.sql.planner.plan.Patterns.applyNode;

/**
 * Given:
 *
 *  * - Apply [X.*, e = EXISTS (true)]
 *   - X
 *   - S with cardinality >= 1
 * 
 * 
 * Produces:
 *
 * 
 * - Project [X.*, e = true]
 *   - X
 * 
 * 
 * Given:
 *
 * 
 * - Apply [X.*, e = EXISTS (true)]
 *   - X
 *   - S with cardinality = 0
 * 
 * 
 * Produces:
 *
 * 
 * - Project [X.*, e = false]
 *   - X
 * 
 */
public class RemoveRedundantExists
        implements Rule
{
    private static final Pattern PATTERN = applyNode()
            .matching(node -> node.getSubqueryAssignments().values().stream().allMatch(ApplyNode.Exists.class::isInstance));

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

    @Override
    public Result apply(ApplyNode node, Captures captures, Context context)
    {
        Assignments.Builder assignments = Assignments.builder();
        assignments.putIdentities(node.getInput().getOutputSymbols());

        Cardinality subqueryCardinality = extractCardinality(node.getSubquery(), context.getLookup());
        Expression result;
        if (subqueryCardinality.isEmpty()) {
            result = FALSE;
        }
        else if (subqueryCardinality.isAtLeastScalar()) {
            result = TRUE;
        }
        else {
            return Result.empty();
        }

        for (Symbol output : node.getSubqueryAssignments().keySet()) {
            assignments.put(output, result);
        }

        return Result.ofPlanNode(new ProjectNode(
                context.getIdAllocator().getNextId(),
                node.getInput(),
                assignments.build()));
    }
}