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Date: Mon, 11 Jul 2016 21:21:11 +0000 (UTC)
From: "Matt McCline (JIRA)" <jira@apache.org>
To: issues@hive.apache.org
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Subject: [jira] [Commented] (HIVE-13974) ORC Schema Evolution doesn't
 support add columns to non-last STRUCT columns
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archived-at: Mon, 11 Jul 2016 21:21:13 -0000


    [ https://issues.apache.org/jira/browse/HIVE-13974?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15371651#comment-15371651 ] 

Matt McCline commented on HIVE-13974:
-------------------------------------


[~owen.omalley] Thanks for looking at this.

No, the semantics of sameCategoryAndAttributes is different than equals.  The TypeDescription.equals method compares (type) id and maximumId which does not work when there is an interior STRUCT column with a different number of columns.  It makes it seem like a type conversion is needed when one is not needed and other parts of the code throw exceptions complaining "no need to convert a STRING to a STRING".

There are 3 kinds of schema not 2.  Part of the problem I'm trying to solve is the ambiguity at different parts of the code as to which schema is being used.  It is the one being returned by the input file format, is it the schema being fed back to the ORC raw merger that included ACID columns, or is it the unconverted file schema.  I don't care what the first 2 schemas are called as long as the names are distinct.  Maybe the names could be reader, internalReader, and file.

About ORC-54 -- it is not practical right now in terms of time.  We have got to get Erie out the door.  We have so little runway left.  I've had 10+ JIRAs for weeks.  Whenever I knock some down more appear.  Also, there really needs to be a parallel HIVE JIRA for it and we must make sure name mapping is fully supported for HIVE.  Given how *difficult* Schema Evolution has been I simply don't believe it will *just work* with ORC only unit tests.

FYI [~hagleitn] [~ekoifman]


> ORC Schema Evolution doesn't support add columns to non-last STRUCT columns
> ---------------------------------------------------------------------------
>
>                 Key: HIVE-13974
>                 URL: https://issues.apache.org/jira/browse/HIVE-13974
>             Project: Hive
>          Issue Type: Bug
>          Components: Hive, ORC, Transactions
>    Affects Versions: 1.3.0, 2.1.0, 2.2.0
>            Reporter: Matt McCline
>            Assignee: Matt McCline
>            Priority: Blocker
>         Attachments: HIVE-13974.01.patch, HIVE-13974.02.patch, HIVE-13974.03.patch, HIVE-13974.04.patch, HIVE-13974.05.WIP.patch, HIVE-13974.06.patch, HIVE-13974.07.patch, HIVE-13974.08.patch, HIVE-13974.09.patch, HIVE-13974.091.patch
>
>
> Currently, the included columns are based on the fileSchema and not the readerSchema which doesn't work for adding columns to non-last STRUCT data type columns.


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