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From "Zheng Shao (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-640) Add LazyBinarySerDe to Hive
Date Wed, 29 Jul 2009 21:02:14 GMT

    [ https://issues.apache.org/jira/browse/HIVE-640?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12736831#action_12736831
] 

Zheng Shao commented on HIVE-640:
---------------------------------

Talked with Yuntao offline.
We want to make sure that LazyBinarySerDe can allow the simplest schema evolution - adding/deleting
columns at the end of the table.

In order to do that, we need to modify LazyBinaryStruct a little bit. We need to write a single
null bytes, then 8 fields, and then the next null byte. This makes sure if data with 8 fields
are read by LazyBinarySerDe intitialized with 9 fields, we can still successfully deserialize
the data (the missing fields will be null).



> Add LazyBinarySerDe to Hive
> ---------------------------
>
>                 Key: HIVE-640
>                 URL: https://issues.apache.org/jira/browse/HIVE-640
>             Project: Hadoop Hive
>          Issue Type: New Feature
>            Reporter: Zheng Shao
>            Assignee: Yuntao Jia
>         Attachments: HIVE-640.1.patch
>
>
> LazyBinarySerDe will serialize the data in binary format while supporting LazyDeserialization.
> This will be used as the SerDe for value between map and reduce, and also between different
map-reduce jobs.
> This will help improve the performance of Hive a lot.

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