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Posted to dev@hive.apache.org by "Gunther Hagleitner (JIRA)" <ji...@apache.org> on 2013/11/15 23:43:20 UTC
[jira] [Commented] (HIVE-5834) Avoid reading ORC footers for files
which will not be split in OrcInputFormat::getSplits()
[ https://issues.apache.org/jira/browse/HIVE-5834?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13824197#comment-13824197 ]
Gunther Hagleitner commented on HIVE-5834:
------------------------------------------
Nice find. LGTM.
> Avoid reading ORC footers for files which will not be split in OrcInputFormat::getSplits()
> ------------------------------------------------------------------------------------------
>
> Key: HIVE-5834
> URL: https://issues.apache.org/jira/browse/HIVE-5834
> Project: Hive
> Issue Type: Improvement
> Components: Tez
> Affects Versions: tez-branch
> Reporter: Gopal V
> Assignee: Gopal V
> Labels: perfomance, split
> Fix For: tez-branch
>
> Attachments: HIVE-5834.00-tez.patch
>
>
> OrcInputFormat::getSplits() fires off a SplitGenerator task for every file in the task.
> The footer & data are on the same node for all files with only 1 hdfs block. On top of that, it will never need a further split as long as its total size is < context.maxSize.
> Reading that footer locally is faster than reading it in the split gen and sending it from the AM.
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