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From "Yi Liu (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-11847) Enhance raw coder allowing to read least required inputs in decoding
Date Tue, 26 May 2015 06:27:18 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-11847?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14558731#comment-14558731
] 

Yi Liu commented on HADOOP-11847:
---------------------------------

Kai, the patch looks good, one comment, +1 after addressing:
In RSRawDecoder#doDecode

{code}
+    for (int bufferIdx = 0, i = 0; i < erasedOrNotToReadIndexes.length; i++) {
+      if (adjustedDirectBufferOutputsParameter[i] == null) {
+        ByteBuffer buffer = checkGetDirectBuffer(bufferIdx, dataLen);
+        buffer.limit(dataLen);
+        adjustedDirectBufferOutputsParameter[i] = resetBuffer(buffer);
+        bufferIdx++;
+      }
+    }
{code}
Here, we need to set buffer position to 0.



> Enhance raw coder allowing to read least required inputs in decoding
> --------------------------------------------------------------------
>
>                 Key: HADOOP-11847
>                 URL: https://issues.apache.org/jira/browse/HADOOP-11847
>             Project: Hadoop Common
>          Issue Type: Sub-task
>          Components: io
>            Reporter: Kai Zheng
>            Assignee: Kai Zheng
>              Labels: BB2015-05-TBR
>         Attachments: HADOOP-11847-HDFS-7285-v3.patch, HADOOP-11847-HDFS-7285-v4.patch,
HADOOP-11847-HDFS-7285-v5.patch, HADOOP-11847-HDFS-7285-v6.patch, HADOOP-11847-HDFS-7285-v7.patch,
HADOOP-11847-HDFS-7285-v8.patch, HADOOP-11847-v1.patch, HADOOP-11847-v2.patch
>
>
> This is to enhance raw erasure coder to allow only reading least required inputs while
decoding. It will also refine and document the relevant APIs for better understanding and
usage. When using least required inputs, it may add computating overhead but will possiblly
outperform overall since less network traffic and disk IO are involved.
> This is something planned to do but just got reminded by [~zhz]' s question raised in
HDFS-7678, also copied here:
> bq.Kai Zheng I have a question about decoding: in a (6+3) schema, if block #2 is missing,
and I want to repair it with blocks 0, 1, 3, 4, 5, 8, how should I construct the inputs to
RawErasureDecoder#decode?
> With this work, hopefully the answer to above question would be obvious.



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