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From "Zheng Shao (JIRA)" <>
Subject [jira] Commented: (HIVE-207) Change SerDe API to allow skipping unused columns
Date Thu, 08 Jan 2009 21:46:59 GMT


Zheng Shao commented on HIVE-207:

It's not trivial to write a thrift DDL to ColumnInfo/TypeInfo converter.  Why don't we directly
go from SQL DDL to TypeInfo?

> Change SerDe API to allow skipping unused columns
> -------------------------------------------------
>                 Key: HIVE-207
>                 URL:
>             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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