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https://issues.apache.org/jira/browse/HIVE-1007?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12795792#action_12795792
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Dave Lerman commented on HIVE-1007:
-----------------------------------
Here's steps to reproduce:
Using Cloudera's Hadoop 0.20.1+152 (since the CombineFile functionality doesn't
work in 0.20.1 without the extra patches), and latest Hive trunk (895060)
SET 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 key from nullscript group by key;
>From the log:
2010-01-01 15:36:18,372 INFO io.CombineHiveInputFormat
(CombineHiveInputFormat.java:getSplits(252)) - CombineHiveInputSplit creating
pool for /user/hive/warehouse/nullscript
2010-01-01 15:36:18,584 INFO mapred.FileInputFormat
(FileInputFormat.java:listStatus(192)) - Total input paths to process : 1
2010-01-01 15:36:18,781 INFO io.CombineHiveInputFormat
(CombineHiveInputFormat.java:getSplits(262)) - number of splits 0
This yields a MR job with 0 mappers and 1 reducer which hangs in Hadoop at 0%.
> 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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