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From "Zheng Shao (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HIVE-207) Change SerDe API to allow skipping unused columns
Date Wed, 07 Jan 2009 03:30:44 GMT

    [ https://issues.apache.org/jira/browse/HIVE-207?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12661424#action_12661424
] 

Zheng Shao commented on HIVE-207:
---------------------------------

@Joydeep - Yes DynamicSerDe is just a parser for thrift DDL. It calls the respective methods
of the protocol for each field. As a result, it's possible to write a protocol without a modifying
the Dynamic SerDe code. I don't get your idea of the extensibility hook. I guess the hook
is just the same as DynamicSerDe and its Protocols?


> Change SerDe API to allow skipping unused columns
> -------------------------------------------------
>
>                 Key: HIVE-207
>                 URL: https://issues.apache.org/jira/browse/HIVE-207
>             Project: Hadoop Hive
>          Issue Type: Bug
>          Components: Query Processor, Serializers/Deserializers
>            Reporter: David Phillips
>
> A deserializer shouldn't have to deserialize columns that are never used by the query
processor.  A serializer shouldn't have to examine unused columns that are known to always
be null.
> As an example, we store data as a Protocol Buffer structure with ~60 fields.  Running
a "select count(1)" currently requires deserializing all fields, which includes checking if
they exist and formatting the data appropriately.  This is expensive and unnecessary.

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