extras/rya.export/export.mongo/src/main/java/org/apache/rya/export/mongo/policy/TimestampPolicyMongoRyaStatementStore.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 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 org.apache.rya.export.mongo.policy;

import static org.apache.rya.export.mongo.MongoRyaStatementStore.TRIPLES_COLLECTION;
import static org.apache.rya.mongodb.dao.SimpleMongoDBStorageStrategy.TIMESTAMP;

import java.util.ArrayList;
import java.util.Date;
import java.util.Iterator;
import java.util.List;

import org.apache.rya.api.domain.RyaStatement;
import org.apache.rya.export.api.conf.policy.TimestampPolicyStatementStore;
import org.apache.rya.export.api.store.FetchStatementException;
import org.apache.rya.export.api.store.RyaStatementStore;
import org.apache.rya.export.mongo.MongoRyaStatementStore;
import org.apache.rya.mongodb.dao.SimpleMongoDBStorageStrategy;
import org.bson.Document;

import com.mongodb.client.MongoCollection;
import com.mongodb.client.MongoCursor;
import com.mongodb.client.MongoDatabase;

/**
 * A {@link RyaStatementStore} decorated to connect to a Mongo database and
 * filter statements based on a timestamp.
 */
public class TimestampPolicyMongoRyaStatementStore extends TimestampPolicyStatementStore {
    private final SimpleMongoDBStorageStrategy adapter;
    private final MongoDatabase db;

    /**
     * Creates a new {@link TimestampPolicyMongoRyaStatementStore}
     * @param store - The {@link MongoRyaStatementStore} to connect to
     * @param timestamp - The Date to filter statements on.
     * @param ryaInstanceName - The rya instance to merge statements to/from.
     */
    public TimestampPolicyMongoRyaStatementStore(final MongoRyaStatementStore store, final Date timestamp, final String ryaInstanceName) {
        super(store, timestamp);
        adapter = new SimpleMongoDBStorageStrategy();
        db = store.getClient().getDatabase(ryaInstanceName);
    }

    @Override
    public Iterator<RyaStatement> fetchStatements() throws FetchStatementException {
        final Document timeObj = new Document()
            .append(SimpleMongoDBStorageStrategy.TIMESTAMP,
                new Document()
                    .append("$gte", timestamp.getTime()));
        final Document sortObj = new Document(TIMESTAMP, 1);
        final MongoCollection<Document> coll = db.getCollection(TRIPLES_COLLECTION);
        final List<RyaStatement> statements = new ArrayList<>();
        try (final MongoCursor<Document> cur = coll.find(timeObj).sort(sortObj).iterator()) {
            while(cur.hasNext()) {
                final RyaStatement statement = adapter.deserializeDocument(cur.next());
                statements.add(statement);
            }
        }
        return statements.iterator();
    }
}