external/storm-cassandra/src/main/java/org/apache/storm/cassandra/bolt/GroupingBatchBuilder.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.storm.cassandra.bolt;

import com.datastax.driver.core.BatchStatement;
import com.google.common.base.Function;
import com.google.common.collect.Iterables;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;
import org.apache.storm.tuple.Tuple;

public class GroupingBatchBuilder implements Iterable<PairBatchStatementTuples> {

    private int batchSizeRows;

    private List<PairStatementTuple> statements;

    /**
     * Creates a new  {@link GroupingBatchBuilder} instance.
     */
    public GroupingBatchBuilder(int batchSizeRows, List<PairStatementTuple> statements) {
        this.batchSizeRows = batchSizeRows;
        this.statements = statements;
    }

    @Override
    public Iterator<PairBatchStatementTuples> iterator() {
        return build().iterator();
    }

    private Iterable<PairBatchStatementTuples> build() {
        Iterable<List<PairStatementTuple>> partition = Iterables.partition(statements, batchSizeRows);
        return Iterables.transform(partition, new Function<List<PairStatementTuple>, PairBatchStatementTuples>() {
            @Override
            public PairBatchStatementTuples apply(List<PairStatementTuple> l) {
                final List<Tuple> inputs = new LinkedList<>();
                final BatchStatement batch = new BatchStatement(BatchStatement.Type.UNLOGGED);
                for (PairStatementTuple pair : l) {
                    batch.add(pair.getStatement());
                    inputs.add(pair.getTuple());
                }
                return new PairBatchStatementTuples(inputs, batch);
            }
        });
    }
}