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