io.trino.sql.ir.optimizer.rule.SimplifyComplementaryLogicalTerms 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.ir.optimizer.rule;

import com.google.common.collect.ImmutableList;
import io.trino.Session;
import io.trino.metadata.Metadata;
import io.trino.sql.PlannerContext;
import io.trino.sql.ir.Call;
import io.trino.sql.ir.Expression;
import io.trino.sql.ir.IsNull;
import io.trino.sql.ir.Logical;
import io.trino.sql.ir.optimizer.IrOptimizerRule;
import io.trino.sql.planner.Symbol;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.Set;

import static io.trino.metadata.GlobalFunctionCatalog.builtinFunctionName;
import static io.trino.sql.ir.IrExpressions.not;
import static io.trino.sql.ir.Logical.Operator.AND;
import static io.trino.sql.ir.Logical.Operator.OR;
import static io.trino.sql.planner.DeterminismEvaluator.isDeterministic;

/**
 * Simplifies logical expression containing terms and negations of those terms.
 * E.g.,
 * 
 *     {@code And(x, $not(x), ...) -> And(x, $is_null(x), ...)}
 *     
{@code Or(x, $not(x), ...) -> Or(x, $not($is_null(x)), ...)}
 * 
 */
public class SimplifyComplementaryLogicalTerms
        implements IrOptimizerRule
{
    private final Metadata metadata;

    public SimplifyComplementaryLogicalTerms(PlannerContext context)
    {
        this.metadata = context.getMetadata();
    }

    @Override
    public Optional apply(Expression expression, Session session, Map bindings)
    {
        if (!(expression instanceof Logical logical)) {
            return Optional.empty();
        }

        Set positives = new HashSet<>();
        Set negatives = new HashSet<>();
        for (Expression term : logical.terms()) {
            if (isDeterministic(term)) {
                if (term instanceof Call not && not.function().name().equals(builtinFunctionName("$not"))) {
                    negatives.add(not.arguments().getFirst());
                }
                else {
                    positives.add(term);
                }
            }
        }

        if (negatives.isEmpty() || positives.isEmpty()) {
            return Optional.empty();
        }

        List newTerms = new ArrayList<>();
        Set seen = new HashSet<>();
        boolean changed = false;
        for (Expression term : logical.terms()) {
            if (isDeterministic(term)) {
                Expression unwrapped = term;
                if (term instanceof Call not && not.function().name().equals(builtinFunctionName("$not"))) {
                    unwrapped = not.arguments().getFirst();
                }

                if (positives.contains(unwrapped) && negatives.contains(unwrapped)) {
                    if (!seen.contains(unwrapped)) {
                        changed = true;
                        newTerms.add(switch (logical.operator()) {
                            case AND -> new Logical(AND, ImmutableList.of(unwrapped, new IsNull(unwrapped)));
                            case OR -> new Logical(OR, ImmutableList.of(unwrapped, not(metadata, new IsNull(unwrapped))));
                        });
                        seen.add(unwrapped);
                    }
                }
                else {
                    newTerms.add(term);
                }
            }
            else {
                newTerms.add(term);
            }
        }

        if (!changed) {
            return Optional.empty();
        }

        if (newTerms.size() == 1) {
            return Optional.of(newTerms.getFirst());
        }

        return Optional.of(new Logical(logical.operator(), newTerms));
    }
}