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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.LimitNode;
import io.trino.sql.planner.plan.PlanNode;
import io.trino.sql.planner.plan.RowNumberNode;

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.rowNumber;

public class PruneRowNumberColumns
        extends ProjectOffPushDownRule
{
    public PruneRowNumberColumns()
    {
        super(rowNumber());
    }

    @Override
    protected Optional pushDownProjectOff(Context context, RowNumberNode rowNumberNode, Set referencedOutputs)
    {
        // Remove unused RowNumberNode
        if (!referencedOutputs.contains(rowNumberNode.getRowNumberSymbol())) {
            if (rowNumberNode.getMaxRowCountPerPartition().isEmpty()) {
                return Optional.of(rowNumberNode.getSource());
            }
            if (rowNumberNode.getPartitionBy().isEmpty()) {
                return Optional.of(new LimitNode(
                        rowNumberNode.getId(),
                        rowNumberNode.getSource(),
                        rowNumberNode.getMaxRowCountPerPartition().get(),
                        false));
            }
        }

        Set requiredInputs = Streams.concat(
                referencedOutputs.stream()
                        .filter(symbol -> !symbol.equals(rowNumberNode.getRowNumberSymbol())),
                rowNumberNode.getPartitionBy().stream(),
                rowNumberNode.getHashSymbol().stream())
                .collect(toImmutableSet());

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