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Graph Database API for Neo4j.

There is a newer version: 5.25.1

/*
 * Copyright (c) "Neo4j"
 * Neo4j Sweden AB [https://neo4j.com]
 *
 * This file is part of Neo4j.
 *
 * Neo4j is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see .
 */
package org.neo4j.graphdb.traversal;

import org.neo4j.graphdb.Path;
import org.neo4j.internal.helpers.collection.LfuCache;

/**
 * Filters on items with a recency within limits of {@link #DEFAULT_RECENT_SIZE}.
 */
class RecentlyUnique extends AbstractUniquenessFilter {
    private static final Object PLACE_HOLDER = new Object();
    private static final int DEFAULT_RECENT_SIZE = 10000;

    private final LfuCache recentlyVisited;

    RecentlyUnique(PrimitiveTypeFetcher type, Object parameter) {
        super(type);
        parameter = parameter != null ? parameter : DEFAULT_RECENT_SIZE;
        recentlyVisited = new LfuCache<>("Recently visited", ((Number) parameter).intValue());
    }

    @Override
    public boolean check(TraversalBranch branch) {
        long id = type.getId(branch);
        boolean add = recentlyVisited.get(id) == null;
        if (add) {
            recentlyVisited.put(id, PLACE_HOLDER);
        }
        return add;
    }

    @Override
    public boolean checkFull(Path path) {
        // See GloballyUnique for comments.
        return true;
    }
}