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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.Streams;
import io.trino.sql.planner.Symbol;
import io.trino.sql.planner.plan.MarkDistinctNode;
import io.trino.sql.planner.plan.PlanNode;

import java.util.Optional;
import java.util.Set;

import static com.google.common.collect.ImmutableSet.toImmutableSet;
import static io.trino.sql.planner.iterative.rule.Util.restrictChildOutputs;
import static io.trino.sql.planner.plan.Patterns.markDistinct;

public class PruneMarkDistinctColumns
        extends ProjectOffPushDownRule
{
    public PruneMarkDistinctColumns()
    {
        super(markDistinct());
    }

    @Override
    protected Optional pushDownProjectOff(Context context, MarkDistinctNode markDistinctNode, Set referencedOutputs)
    {
        if (!referencedOutputs.contains(markDistinctNode.getMarkerSymbol())) {
            return Optional.of(markDistinctNode.getSource());
        }

        Set requiredInputs = Streams.concat(
                referencedOutputs.stream()
                        .filter(symbol -> !symbol.equals(markDistinctNode.getMarkerSymbol())),
                markDistinctNode.getDistinctSymbols().stream(),
                markDistinctNode.getHashSymbol().stream())
                .collect(toImmutableSet());

        return restrictChildOutputs(context.getIdAllocator(), markDistinctNode, requiredInputs);
    }
}