org.veronicadb.core.memorygraph.VSubGraph.java Source code

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Here is the source code for org.veronicadb.core.memorygraph.VSubGraph.java

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/*
 * Copyright 2015 Ambud Sharma
 * 
 * This program 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 <http://www.gnu.org/licenses/>.2
 */
package org.veronicadb.core.memorygraph;

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

import org.veronicadb.core.structures.ReadOnlyShardException;
import org.veronicadb.core.structures.ShardInitializationException;
import org.veronicadb.core.structures.VElement.IdGenerator;
import org.veronicadb.core.structures.VGraphShard;
import org.veronicadb.core.structures.VVertex;

import com.google.common.hash.BloomFilter;
import com.google.common.hash.Funnels;

/**
 * A SubGraph is the way Veronica performs sharding of the graph. Since a graph can be thought of as a graph of one or more 
 * smaller graphs this theory can be applied to effectively shard the graph database based on a selected sharding strategy.
 * 
 * Sharding is critical to any concurrent database as is the strategy used to shard. Performing sharding in a logical 
 * fashion provides better native performance while keeping Veronica relatively simple to understand.
 * 
 * Deletes are currently not supported.
 * 
 * @author ambudsharma
 *
 */
public class VSubGraph extends VGraphShard {

    private ConcurrentMap<Long, VVertex> shardVertices;
    // bloom filter for the vertices in this subgraph
    private BloomFilter<Long> subGraphBloom;

    public VSubGraph(long graphId, int shardSize) {
        super(graphId, shardSize);
        shardVertices = new ConcurrentHashMap<Long, VVertex>();
        subGraphBloom = BloomFilter.create(Funnels.longFunnel(), shardSize, 0.0001);
        isReadOnly().set(false);
    }

    @Override
    public void init() throws ShardInitializationException {
    }

    @Override
    public VVertex addVertex(String id, String label) throws ReadOnlyShardException {
        VVertex vertex = new VVertex(this, id, label);
        addVertex(vertex);
        return vertex;
    }

    @Override
    protected void addVertex(VVertex vertex) throws ReadOnlyShardException {
        if (isReadOnly().get()) {
            throw new ReadOnlyShardException("This subgraph is readonly");
        }
        synchronized (subGraphBloom) {
            subGraphBloom.put(vertex.getId());
        }
        shardVertices.put(vertex.getId(), vertex);
    }

    /**
     * Lookup hash and return vertex id if one exists
     * @param vertexId
     * @return vertexId
     */
    public VVertex getVertex(long vertexId) {
        return shardVertices.get(vertexId);
    }

    public VVertex getVertex(String vertexId) {
        return getVertex(vertexId, null);
    }

    public VVertex getVertex(String id, String label) {
        if (label != null)
            return shardVertices.get(IdGenerator.hash(id + "_" + label));
        else
            return shardVertices.get(IdGenerator.hash(id));
    }

    /**
     * @return the graphId
     */
    public Long getGraphId() {
        return getShardId();
    }

    /**
     * @return the shardVertices
     */
    public List<VVertex> getShardVertices() {
        return new ArrayList<VVertex>(shardVertices.values());
    }

    /**
     * Is vertex present in this subgraph / graph shard
     * @param vertexId
     * @return if vertex might be present in this subgraph
     */
    @Override
    public boolean vertexExists(long vertexId) {
        return subGraphBloom.mightContain(vertexId);
    }

    public boolean vertexExists(String vertexId) {
        return subGraphBloom.mightContain(IdGenerator.hash(vertexId));
    }

    /**
     * Re-initialize this shard from external data. Re-initialized shards are read-only by default
     * @param bloomBytes
     * @param vertices
     * @throws IOException
     */
    public void reinit(byte[] bloomBytes, List<VVertex> vertices) throws IOException {
        loadBloom(bloomBytes);
        loadVertices(vertices);
        isReadOnly().set(false);
    }

    /**
     * Load all vertices from the list to the hashmap
     * @param vertices
     */
    public void loadVertices(List<VVertex> vertices) {
        vertices.stream().parallel().forEach(vertex -> shardVertices.put(vertex.getId(), vertex));
    }

    /**
     * Re-initialize bloomfilter from bytes
     * @param bloomBytes
     * @throws IOException
     */
    protected void loadBloom(byte[] bloomBytes) throws IOException {
        subGraphBloom = BloomFilter.readFrom(new ByteArrayInputStream(bloomBytes), Funnels.longFunnel());
    }

    /**
     * @return bytes of the Bloom Filter
     * @throws IOException
     */
    public byte[] getBloomBytes() throws IOException {
        ByteArrayOutputStream os = new ByteArrayOutputStream(1000);
        BloomFilter<Long> clone = null;
        synchronized (subGraphBloom) {
            clone = subGraphBloom.copy();
        }
        clone.writeTo(os);
        return os.toByteArray();
    }

    /**
     * @return if shard is cached into memory
     */
    public boolean isCached() {
        return shardVertices.size() > 0;
    }

    /**
     * Clear this shard of data but indices and bloomfilter will remain in memory
     */
    public void clearShard() {
        shardVertices.clear();
    }

}