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From "Xuefu Zhang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-5298) AvroSerde performance problem caused by HIVE-3833
Date Fri, 27 Sep 2013 19:52:03 GMT

    [ https://issues.apache.org/jira/browse/HIVE-5298?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13780304#comment-13780304
] 

Xuefu Zhang commented on HIVE-5298:
-----------------------------------

[~ashutoshc] Thanks for pointing that out. My initial investigation shows that onefile is
indeed a table or partition location (directory). On that ground, the patch shouldn't have
much performance improvement. I'm working with QA to find out the reason for the reported
performance gain, and will close this JIRA unless we are clear on this. Thanks again for your
feedback.
                
> AvroSerde performance problem caused by HIVE-3833
> -------------------------------------------------
>
>                 Key: HIVE-5298
>                 URL: https://issues.apache.org/jira/browse/HIVE-5298
>             Project: Hive
>          Issue Type: Improvement
>          Components: Query Processor
>    Affects Versions: 0.11.0
>            Reporter: Xuefu Zhang
>            Assignee: Xuefu Zhang
>             Fix For: 0.13.0
>
>         Attachments: HIVE-5298.1.patch, HIVE-5298.patch
>
>
> HIVE-3833 fixed the targeted problem and made Hive to use partition-level metadata to
initialize object inspector. In doing that, however, it goes thru every file under the table
to access the partition metadata, which is very inefficient, especially in case of multiple
files per partition. This causes more problem for AvroSerde because AvroSerde initialization
accesses schema, which is located on file system. As a result, before hive can process any
data, it needs to access every file for a table, which can take long enough to cause job failure
because of lack of job progress.
> The improvement can be made so that partition metadata is only access once per partition.

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