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https://issues.apache.org/jira/browse/HIVE-20523?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16630911#comment-16630911
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George Pachitariu commented on HIVE-20523:
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Hi Zoltan Haindrich, can you please have a look at this patch?
I have looked at the failed tests. They all failed because the expected raw
data size has changed, which is the expected behaviour of this patch.
> Improve table statistics for Parquet format
> -------------------------------------------
>
> Key: HIVE-20523
> URL: https://issues.apache.org/jira/browse/HIVE-20523
> Project: Hive
> Issue Type: Improvement
> Components: Physical Optimizer
> Reporter: George Pachitariu
> Assignee: George Pachitariu
> Priority: Minor
> Attachments: HIVE-20523.1.patch, HIVE-20523.2.patch,
> HIVE-20523.3.patch, HIVE-20523.4.patch, HIVE-20523.5.patch,
> HIVE-20523.6.patch, HIVE-20523.patch
>
>
> Right now, in the table basic statistics, the *raw data size* for a row with
> any data type in the Parquet format is 1. This is an underestimated value
> when columns are complex data structures, like arrays.
> Having tables with underestimated raw data size makes Hive assign less
> containers (mappers/reducers) to it, making the overall query slower.
> Heavy underestimation also makes Hive choose MapJoin instead of the
> ShuffleJoin that can fail with OOM errors.
> In this patch, I compute the columns data size better, taking into account
> complex structures. I followed the Writer implementation for the ORC format.
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