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https://issues.apache.org/jira/browse/HIVE-18234?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Aihua Xu resolved HIVE-18234.
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Resolution: Not A Bug
[~hengyu.dai] Can you try on the newer version with the fix?
> Hive MergeFileTask doesn't work correctly
> -----------------------------------------
>
> Key: HIVE-18234
> URL: https://issues.apache.org/jira/browse/HIVE-18234
> Project: Hive
> Issue Type: Bug
> Components: Hive
> Affects Versions: 2.1.1
> Reporter: Hengyu Dai
> Assignee: Aihua Xu
>
> For MergeFileTask, Hive will read hive.merge.mapfiles,
> hive.merge.mapredfiles, hive.merge.size.per.task,
> hive.merge.smallfiles.avgsize these property to determine whether to generate
> a MergeFileTask to merge small files, if merge is needed, then hive will
> generate a MergeFileTask/MapWork to merge files, the property will finally be
> set to MapWork#maxSplitSize, maxSplitSize#minSplitSize,
> maxSplitSize#minSplitSizePerNode, minSplitSizePerRack#minSplitSizePerRack.
> But Hive doesn't use these settings when commit Map task to Hadoop, i.e.,
> the corresponding settings of Hadoop: "mapred.max.split.size"
> "mapred.min.split.size.per.node" "mapred.min.split.size.per.rack" are not set
> by these Hive setting. SO, those Hive setting does not take effect for
> MergeFileTask.
> steps to reproduce:
> this sql will still produce many small files(less than 20MB)
> {code:sql}
> set hive.merge.mapredfiles=true;
> set hive.merge.mapfiles=true;
> set hive.merge.smallfiles.avgsize=500000000;
> set hive.merge.size.per.task=1000000000;
> insert overwrite table foo partition(dt='20171203')
> select * from bar;
> {code}
> to fix this problem, I think we should set these property to Hadoop in
> MergeFileTask,
> the following code works me
> {code:java}
> // in MergeFileTask#execute()
> job.setInputFormat(work.getInputformatClass());
> job.setOutputFormat(HiveOutputFormatImpl.class);
> job.setMapperClass(MergeFileMapper.class);
> job.setMapOutputKeyClass(NullWritable.class);
> job.setMapOutputValueClass(NullWritable.class);
> job.setOutputKeyClass(NullWritable.class);
> job.setOutputValueClass(NullWritable.class);
> job.setNumReduceTasks(0);
> // set these property
> job.setLong("mapred.max.split.size", work.getMaxSplitSize());
> job.setLong("mapred.min.split.size.per.rack",
> work.getMinSplitSizePerRack());
> job.setLong("mapred.min.split.size.per.node",
> work.getMinSplitSizePerNode());
> {code}
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