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https://issues.apache.org/jira/browse/HBASE-1856?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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stack resolved HBASE-1856.
--------------------------
Resolution: Fixed
Hadoop Flags: [Reviewed]
Committed branch and trunk (with Lars's suggestion).
> HBASE-1765 broke MapReduce when using Result.list()
> ---------------------------------------------------
>
> Key: HBASE-1856
> URL: https://issues.apache.org/jira/browse/HBASE-1856
> Project: Hadoop HBase
> Issue Type: Bug
> Affects Versions: 0.20.1, 0.21.0
> Reporter: Lars George
> Assignee: Lars George
> Priority: Critical
> Fix For: 0.20.1
>
> Attachments: 1856.patch
>
>
> Not sure if it is just me, but using MR over HBase employing a TableReducer
> is not working. After the first row is read all subsequent rows get the same
> Result's of that very first row. After tracing this from the Map phase I
> found the culprit in Result and the HBASE-1765 delayed field parsing change.
> This is the code I use in the reduce():
> {code}
> @Override
> protected void reduce(ImmutableBytesWritable key, Iterable<Result> values,
> Context context) throws IOException, InterruptedException {
> String skey = Bytes.toString(key.get());
> context.getCounter(CountersTotals.ROWS).increment(1);
> for (Result result : values) {
> for (KeyValue kv: result.list()) {
> try {
> if (LOG.isDebugEnabled()) LOG.debug("reduce: key -> " + skey + ",
> kv -> " + kv);
> ...
> {code}
> Here is the current list() implementation:
> {code}
> public List<KeyValue> list() {
> if(this.kvs == null) {
> readFields();
> }
> return isEmpty()? null: Arrays.asList(sorted());
> }
> {code}
> The problem is that readFields(DataInput) does not clear kvs!
> {code}
> public void readFields(final DataInput in)
> throws IOException {
> familyMap = null;
> row = null;
> int totalBuffer = in.readInt();
> if(totalBuffer == 0) {
> bytes = null;
> return;
> }
> byte [] raw = new byte[totalBuffer];
> in.readFully(raw, 0, totalBuffer);
> bytes = new ImmutableBytesWritable(raw, 0, totalBuffer);
> }
> {code}
> The above is called by the MR framework's WritableSerialization for each map
> output. But since "kvs" is already set "list()" returns the old data!
> I assume the only change needed is clearing kvs as well:
> {code}
> public void readFields(final DataInput in)
> throws IOException {
> familyMap = null;
> row = null;
> kvs = null;
> ....
> {code}
> I'll test that now and report.
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