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