cassandra-trunk/tools/fqltool/src/org/apache/cassandra/fqltool/commands/Compare.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.cassandra.fqltool.commands;


import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.stream.Collectors;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.collect.AbstractIterator;

import io.airlift.airline.Arguments;
import io.airlift.airline.Command;
import io.airlift.airline.Option;
import net.openhft.chronicle.core.io.Closeable;
import net.openhft.chronicle.queue.ChronicleQueue;
import net.openhft.chronicle.queue.impl.single.SingleChronicleQueueBuilder;
import net.openhft.chronicle.queue.ExcerptTailer;
import org.apache.cassandra.fqltool.FQLQueryIterator;
import org.apache.cassandra.fqltool.ResultHandler;
import org.apache.cassandra.fqltool.StoredResultSet;

/**
 */
@Command(name = "compare", description = "Compare result files generated by fqltool replay")
public class Compare implements Runnable
{
    @Arguments(usage = "<path1> [<path2>...<pathN>]",
               description = "Directories containing result files to compare.",
               required = true)
    private List<String> arguments = new ArrayList<>();

    @Option(title = "queries",
            name = { "--queries"},
            description = "Directory to read the queries from. It is produced by the fqltool replay --store-queries option. ",
            required = true)
    private String querylog;

    @Override
    public void run()
    {
        compare(querylog, arguments);
    }

    public static void compare(String querylog, List<String> arguments)
    {
        List<ChronicleQueue> readQueues = null;
        try (ResultHandler rh = new ResultHandler(arguments, null, null);
             ChronicleQueue queryQ = SingleChronicleQueueBuilder.single(querylog).readOnly(true).build();
             FQLQueryIterator queries = new FQLQueryIterator(queryQ.createTailer(), 1))
        {
            readQueues = arguments.stream().map(s -> SingleChronicleQueueBuilder.single(s).readOnly(true).build()).collect(Collectors.toList());
            List<Iterator<ResultHandler.ComparableResultSet>> its = readQueues.stream().map(q -> new StoredResultSetIterator(q.createTailer())).collect(Collectors.toList());
            while (queries.hasNext())
                rh.handleResults(queries.next(), resultSets(its));
        }
        catch (Exception e)
        {
            throw new RuntimeException(e);
        }
        finally
        {
            if (readQueues != null)
                readQueues.forEach(Closeable::close);
        }
    }

    @VisibleForTesting
    public static List<ResultHandler.ComparableResultSet> resultSets(List<Iterator<ResultHandler.ComparableResultSet>> its)
    {
        List<ResultHandler.ComparableResultSet> resultSets = new ArrayList<>(its.size());
        for (Iterator<ResultHandler.ComparableResultSet> it : its)
        {
            if (it.hasNext())
                resultSets.add(it.next());
            else
                resultSets.add(null);
        }
        return resultSets;
    }

    @VisibleForTesting
    public static class StoredResultSetIterator extends AbstractIterator<ResultHandler.ComparableResultSet>
    {
        private final ExcerptTailer tailer;

        public StoredResultSetIterator(ExcerptTailer tailer)
        {
            this.tailer = tailer;
        }

        protected ResultHandler.ComparableResultSet computeNext()
        {
            StoredResultSet srs = StoredResultSet.fromTailer(tailer);
            if (srs.hasMoreResultSets)
                return srs;
            return endOfData();
        }
    }


}
