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From "Gunther Hagleitner (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-7971) Support alter table change/replace/add columns for existing partitions
Date Fri, 12 Sep 2014 19:03:33 GMT

    [ https://issues.apache.org/jira/browse/HIVE-7971?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14131948#comment-14131948
] 

Gunther Hagleitner commented on HIVE-7971:
------------------------------------------

Comments on rb

I think we should document when this is useful:

- when to use the table level statement (regular schema update for new partitions)
- you're only changing a partition's schema, not the table
- this will just re-interpret the existing partition's data
- this is meant to fix broken partitions (decimal hive12 -> hive13)

Also, unless you allow changing multiple partitions at once, it will still be a pain to update
all partitions after an upgrade to hive 13. There might be thousands.

> Support alter table change/replace/add columns for existing partitions
> ----------------------------------------------------------------------
>
>                 Key: HIVE-7971
>                 URL: https://issues.apache.org/jira/browse/HIVE-7971
>             Project: Hive
>          Issue Type: Bug
>            Reporter: Jason Dere
>            Assignee: Jason Dere
>         Attachments: HIVE-7971.1.patch
>
>
> ALTER TABLE CHANGE COLUMN is allowed for tables, but not for partitions. Same for add/replace
columns.
> Allowing this for partitions can be useful in some cases. For example, one user has tables
with Hive 0.12 Decimal columns, which do not specify precision/scale. To be able to properly
read the decimal values from the existing partitions, the column types in the partitions need
to be changed to decimal types with precision/scale.



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