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From "Bhallamudi Venkata Siva Kamesh (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (MAPREDUCE-3952) In MR2, when Total input paths to process == 1, CombinefileInputFormat.getSplits() returns 0 split.
Date Sat, 03 Mar 2012 19:33:59 GMT

    [ https://issues.apache.org/jira/browse/MAPREDUCE-3952?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13221679#comment-13221679
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Bhallamudi Venkata Siva Kamesh commented on MAPREDUCE-3952:
-----------------------------------------------------------

@Zhenxiao
bq. Is it the case that, in MR1, an empty file get a split size of 1, and then the record
reader will emit no records. And in MR2, an empty file get a split size of 0?

Yes.  
In MR1, in CombineFileInputFormat#OneFileInfo, *OneBlockInfo* object has been created even
if the file's size is 0 and this leads to the creation of a file split of lenght 0. Where
as in MR2, we are skipping the creation of this object and hence no file split(s).	

                
> In MR2, when Total input paths to process == 1, CombinefileInputFormat.getSplits() returns
0 split.
> ---------------------------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-3952
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-3952
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: mrv2
>            Reporter: Zhenxiao Luo
>
> Hive get unexpected result when using MR2(When using MR1, always get expected result).
> In MR2, when Total input paths to process == 1, CombinefileInputFormat.getSplits() returns
0 split.
> The calling code in Hive, in Hadoop23Shims.java:
> InputSplit[] splits = super.getSplits(job, numSplits);
> this get splits.length == 0.
> In MR1, everything goes fine, the calling code in Hive, in Hadoop20Shims.java:
> CombineFileSplit[] splits = (CombineFileSplit[]) super.getSplits(job, numSplits);
> this get splits.length == 1.

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