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https://issues.apache.org/jira/browse/HIVE-207?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12661380#action_12661380
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Jeff Hammerbacher commented on HIVE-207:
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I learned a lot, too. Could someone with a handle on Hive compress this
discussion into reusable documentation and post it to the Hive site?
> 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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