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From "Namit Jain (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-1007) CombinedHiveInputFormat fails with empty input
Date Tue, 22 Dec 2009 20:54:29 GMT

    [ https://issues.apache.org/jira/browse/HIVE-1007?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12793779#action_12793779
] 

Namit Jain commented on HIVE-1007:
----------------------------------

 jar -xvf ./build/hadoopcore/hadoop-0.20.0/hadoop-0.20.0-core.jar

Using hadoop.version 0.20.0,

The following test works fine:

 t hive.input.format=org.apache.hadoop.hive.ql.io.CombineHiveInputFormat;

DROP TABLE nullscript;
CREATE TABLE nullscript(KEY STRING, VALUE STRING) STORED AS TEXTFILE;

LOAD DATA LOCAL INPATH '../data/files/nullfile.txt' INTO TABLE nullscript;

select transform(key) using '/bin/cat' as key1 from nullscript;


DROP TABLE nullscript;



and we can 1 split:

    [junit] 09/12/22 10:45:24 INFO io.CombineHiveInputFormat: number of splits 1


Seems like a hadoop bug

> CombinedHiveInputFormat fails with empty input
> ----------------------------------------------
>
>                 Key: HIVE-1007
>                 URL: https://issues.apache.org/jira/browse/HIVE-1007
>             Project: Hadoop Hive
>          Issue Type: Bug
>          Components: Query Processor
>    Affects Versions: 0.4.1
>            Reporter: Dave Lerman
>            Assignee: Dave Lerman
>         Attachments: hive.1007.1.patch
>
>
> In a multi-stage query, when one stage returns no data (resulting in a bunch of output
files with size 0), the next stage creates a job with 0 mappers which just sits in the Hadoop
task track forever and hangs the query at 0%.  The issue is that CombineHiveInputFormat looks
for blocks to populate splits, find nones (since input is all 0 bytes), and then returns an
empty array from getSplits.
> There may be good a way to just skip that job altogether, but as a quick hack to get
it working, when there are no splits, I just create a single empty one using the first path
so that the job doesn't hang.

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