[jira] [Commented] (AVRO-806) add a column-major codec for data files

["Jeff Hammerbacher (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/AVRO-806?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13058166#comment-13058166 ] 

Jeff Hammerbacher commented on AVRO-806:
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> I think the advantage of a columnar format is to avoid touching data that's not needed, and avoiding decompression is consistent with that.

During the design of RCFile, the folks from Facebook found that packing a few columns together into a file made for better performance than putting a single column into the file. There's a trade-off between CPU consumed in deserialization and IO consumed in pulling the data off of disk. Avoiding decompressing columns that are not accessed seemed to be important for Hive performance.

> add a column-major codec for data files
> ---------------------------------------
>
>                 Key: AVRO-806
>                 URL: https://issues.apache.org/jira/browse/AVRO-806
>             Project: Avro
>          Issue Type: New Feature
>          Components: java, spec
>            Reporter: Doug Cutting
>            Assignee: Doug Cutting
>         Attachments: AVRO-806-v2.patch, AVRO-806.patch, avro-file-columnar.pdf
>
>
> Define a codec that, when a data file's schema is a record schema, writes blocks within the file in column-major order.  This would permit better compression and also permit efficient skipping of fields that are not of interest.

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