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Date: Thu, 6 Jul 2017 06:17:00 +0000 (UTC)
From: "Hao Zhong (JIRA)" <jira@apache.org>
To: commits@cassandra.apache.org
Message-ID: <JIRA.13085099.1499321777000.181190.1499321820105@Atlassian.JIRA>
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Subject: [jira] [Created] (CASSANDRA-13676) Some serializers depend on
 Stream-specific methods
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archived-at: Thu, 06 Jul 2017 06:17:05 -0000

Hao Zhong created CASSANDRA-13676:
-------------------------------------

             Summary: Some serializers depend on Stream-specific methods
                 Key: CASSANDRA-13676
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-13676
             Project: Cassandra
          Issue Type: Bug
            Reporter: Hao Zhong


When fixing CASSANDRA-2382, Jonathan Ellis complained that some serializers did (do?) depend on Stream-specific methods. The buggy code is as follow:
{code}
public static class EstimatedHistogramSerializer implements ICompactSerializer<EstimatedHistogram>
    {
        public void serialize(EstimatedHistogram eh, DataOutputStream dos) throws IOException
        {
            long[] offsets = eh.getBucketOffsets();
            long[] buckets = eh.getBuckets(false);
            dos.writeInt(buckets.length);
            for (int i = 0; i < buckets.length; i++)
            {
                dos.writeLong(offsets[i == 0 ? 0 : i - 1]);
                dos.writeLong(buckets[i]);
            }
        }

        public EstimatedHistogram deserialize(DataInputStream dis) throws IOException
        {
            int size = dis.readInt();
            long[] offsets = new long[size - 1];
            long[] buckets = new long[size];

            for (int i = 0; i < size; i++) {
                offsets[i == 0 ? 0 : i - 1] = dis.readLong();
                buckets[i] = dis.readLong();
            }
            return new EstimatedHistogram(offsets, buckets);
        }
    }
{code}
The fixed code is:
{code}
public static class EstimatedHistogramSerializer implements ICompactSerializer2<EstimatedHistogram>
    {
        public void serialize(EstimatedHistogram eh, DataOutput dos) throws IOException
        {
            long[] offsets = eh.getBucketOffsets();
            long[] buckets = eh.getBuckets(false);
            dos.writeInt(buckets.length);
            for (int i = 0; i < buckets.length; i++)
            {
                dos.writeLong(offsets[i == 0 ? 0 : i - 1]);
                dos.writeLong(buckets[i]);
            }
        }

        public EstimatedHistogram deserialize(DataInput dis) throws IOException
        {
            int size = dis.readInt();
            long[] offsets = new long[size - 1];
            long[] buckets = new long[size];

            for (int i = 0; i < size; i++) {
                offsets[i == 0 ? 0 : i - 1] = dis.readLong();
                buckets[i] = dis.readLong();
            }
            return new EstimatedHistogram(offsets, buckets);
        }
    }
{code}
I notice that some serializers still depend on Stream-specific methods. For example, the IndexSummary_deserialize method has the following code:
{code}
 public IndexSummary deserialize(DataInputStream in, IPartitioner partitioner, int expectedMinIndexInterval, int maxIndexInterval) throws IOException
        {
            int minIndexInterval = in.readInt();
            if (minIndexInterval != expectedMinIndexInterval)
            {
                throw new IOException(String.format("Cannot read index summary because min_index_interval changed from %d to %d.",
                                                    minIndexInterval, expectedMinIndexInterval));
            }

            int offsetCount = in.readInt();
            long offheapSize = in.readLong();
            int samplingLevel = in.readInt();
            int fullSamplingSummarySize = in.readInt();

            int effectiveIndexInterval = (int) Math.ceil((BASE_SAMPLING_LEVEL / (double) samplingLevel) * minIndexInterval);
            if (effectiveIndexInterval > maxIndexInterval)
            {
                throw new IOException(String.format("Rebuilding index summary because the effective index interval (%d) is higher than" +
                                                    " the current max index interval (%d)", effectiveIndexInterval, maxIndexInterval));
            }

            Memory offsets = Memory.allocate(offsetCount * 4);
            Memory entries = Memory.allocate(offheapSize - offsets.size());
            try
            {
                FBUtilities.copy(in, new MemoryOutputStream(offsets), offsets.size());
                FBUtilities.copy(in, new MemoryOutputStream(entries), entries.size());
            }
            catch (IOException ioe)
            {
                offsets.free();
                entries.free();
                throw ioe;
            }
            // our on-disk representation treats the offsets and the summary data as one contiguous structure,
            // in which the offsets are based from the start of the structure. i.e., if the offsets occupy
            // X bytes, the value of the first offset will be X. In memory we split the two regions up, so that
            // the summary values are indexed from zero, so we apply a correction to the offsets when de/serializing.
            // In this case subtracting X from each of the offsets.
            for (int i = 0 ; i < offsets.size() ; i += 4)
                offsets.setInt(i, (int) (offsets.getInt(i) - offsets.size()));
            return new IndexSummary(partitioner, offsets, offsetCount, entries, entries.size(), fullSamplingSummarySize, minIndexInterval, samplingLevel);
        }
{code}
Is it worthy replace the Stream-specific inputs as well?


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