hugegraph-server/hugegraph-core/src/main/java/org/apache/hugegraph/traversal/optimize/HugeGraphStepStrategy.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements. See the NOTICE file distributed with this
 * work for additional information regarding copyright ownership. The ASF
 * licenses this file to You 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
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 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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package org.apache.hugegraph.traversal.optimize;

import java.util.Collections;
import java.util.List;
import java.util.Set;

import org.apache.tinkerpop.gremlin.process.traversal.Traversal;
import org.apache.tinkerpop.gremlin.process.traversal.TraversalStrategy.ProviderOptimizationStrategy;
import org.apache.tinkerpop.gremlin.process.traversal.step.map.GraphStep;
import org.apache.tinkerpop.gremlin.process.traversal.strategy.AbstractTraversalStrategy;
import org.apache.tinkerpop.gremlin.process.traversal.util.TraversalHelper;

public final class HugeGraphStepStrategy
             extends AbstractTraversalStrategy<ProviderOptimizationStrategy>
             implements ProviderOptimizationStrategy {

    private static final long serialVersionUID = -2952498905649139719L;

    private static final HugeGraphStepStrategy INSTANCE;

    static {
        INSTANCE = new HugeGraphStepStrategy();
    }

    private HugeGraphStepStrategy() {
        // pass
    }

    @Override
    @SuppressWarnings({ "rawtypes", "unchecked" })
    public void apply(Traversal.Admin<?, ?> traversal) {
        TraversalUtil.convAllHasSteps(traversal);

        // Extract conditions in GraphStep
        List<GraphStep> steps = TraversalHelper.getStepsOfClass(
                                GraphStep.class, traversal);
        for (GraphStep originStep : steps) {
            TraversalUtil.trySetGraph(originStep,
                                      TraversalUtil.tryGetGraph(steps.get(0)));

            HugeGraphStep<?, ?> newStep = new HugeGraphStep<>(originStep);
            TraversalHelper.replaceStep(originStep, newStep, traversal);

            TraversalUtil.extractHasContainer(newStep, traversal);

            // TODO: support order-by optimize
            // TraversalUtil.extractOrder(newStep, traversal);

            TraversalUtil.extractRange(newStep, traversal, false);

            TraversalUtil.extractCount(newStep, traversal);
        }
    }

    @Override
    public Set<Class<? extends ProviderOptimizationStrategy>> applyPost() {
        return Collections.singleton(HugeCountStepStrategy.class);
    }

    public static HugeGraphStepStrategy instance() {
        return INSTANCE;
    }
}