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Hive >> mail # user >> FROM INSERT after ADD COLUMN


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yaboulna@... 2012-12-10, 00:35
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Connell, Chuck 2012-12-10, 00:53
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Shreepadma Venugopalan 2012-12-10, 00:53
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Re: FROM INSERT after ADD COLUMN
Hello Shreepadma,

That's definitely very helpful. I doubted that this would be the case,  
but I was thinking that maybe there's a way to do it using a merge  
task. I will change my data structure to make it a bit like HBase, and  
I hope Hive would still be the right choice for me.. it can be backed  
by HBase anyway :). Thank you very much, your quick reply saved me a  
lot of time!

Sincerely,
Younos

Quoting Shreepadma Venugopalan <[EMAIL PROTECTED]>:

> Hi Younos,
>
> Since HiveQL doesn't support an insert..value statement, you can't insert
> values into a specific column. Let's assume your table had the following
> structure before the alter table..add columns statement was executed,
>
> tab (a string, b bigint, c double)
>
> Furthermore, let's assume that it had 100 rows. Now, let's assume you did
> an alter table tab add columns (d binary). The new table structure will
> look like below,
>
> tab (a string, b bigint, c double, d binary)
>
> You can't insert binary data into the 100 rows that were present prior to
> the alter table statement by executing a HiveQL statement. HiveQL doesn't
> support an insert..values statement like most RDBMSs. However, you can
> delete the existing files and add new files that contain records
> corresponding to the new table structure. Alternatively, you can skip the
> deletion step and just add new files that correspond to the new table
> structure. When you execute a HiveQL query, null will be returned for those
> columns for which the data doesn't exist.
>
> Hope this helps.
>
> Thanks.
> Shreepadma
>
>
> On Sun, Dec 9, 2012 at 4:35 PM, <[EMAIL PROTECTED]> wrote:
>
>> Hello,
>>
>> I couldn't find any example of how to populate columns that were added to
>> a table. How would Hive tell which row to append by each value of the newly
>> added columns? Does it do a column name matching?
>>
>> Sincerely,
>> Younos
>>
>>
>>
>>
>

Best regards,
Younos Aboulnaga

Masters candidate
David Cheriton school of computer science
University of Waterloo
http://cs.uwaterloo.ca

E-Mail: [EMAIL PROTECTED]
Mobile: +1 (519) 497-5669
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Bertrand Dechoux 2012-12-10, 06:32
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Shreepadma Venugopalan 2012-12-10, 18:32
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Shreepadma Venugopalan 2012-12-10, 18:36
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yaboulna@... 2012-12-10, 20:01