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From "qq" <987626...@qq.com>
Subject 回复: 回复: How to limit the number of rows to export data when using sqoopto export data from hdfs to oracle?
Date Sat, 02 Dec 2017 06:49:50 GMT
I created a hive view, through sqoop export data to oracle , the error message is as follows:
ERROR tool.ExporTool:Encoountered IOException running export job:java.io.IOException:java.lang.NullPointerException
Is sqoop currently exporting hive view data?




------------------ 原始邮件 ------------------
发件人: "Markus Kemper"<markus@cloudera.com>; 
发送时间: 2017年12月1日(星期五) 晚上9:24
收件人: "user"<user@sqoop.apache.org>; 
主题: Re: 回复: How to limit the number of rows to export data when using sqoopto export
data from hdfs to oracle?



Hey Team,

Not sure a VIEW with export will work.  If I recall export with --hcatalog is not aware of
HMS VIEWs, need to test.




Markus Kemper
Customer Operations Engineer





 
On Fri, Dec 1, 2017 at 8:00 AM, Attila Szabó <maugli@apache.org> wrote:
Hey, 

IMHO it's CTAS which stands for "Create Table As Select". 


On the front of views :
The question is more than valid if Sqoop supports it or not. I do remember a problem we've
faced 1-1.5 year ago in connection with Hive + Hcatalog + Sqoop,  and that was not supported
because of some missing Hive Serde implementation. I'm not sure if this problem exists with
standard Hive views and Sqoop export command, but you should give a try. 


The thing what could be problematic with views:
A View is a result of a select statement by design. But in Hive every HiveQL command is translated
to a map/reduce job. But Sqoop also works with map/reduce jobs and thus it tries to read files
from the HDFS ( because of data locality and things), so this might be a clashing problem
here, but as I've advised you should give it a try.


With CTAS:
It should definitely work, because in this case Hive will store the filtered results in a
different Hive table ( == HDFS directory)  and thus export dir is your friend. :) 


Were I able to clarify everything or do you have further questions? 


Cheers, 
Attila 


On Dec 1, 2017 1:33 PM, "qq" <987626311@qq.com> wrote:
Hello:
      First of all, thank you very much for your answer, I just started to touch sqoop, there
are many do not understand, you can explain in detail about the operation steps of sqoop export
work with views and the steps of exact dataset to sqoop using a CAST?

     thinks.
     I am looking forward to your reply!




------------------ 原始邮件 ------------------
发件人: "Per Ullberg";<per.ullberg@klarna.com>;
发送时间: 2017年12月1日(星期五) 晚上6:21
收件人: "user"<user@sqoop.apache.org>;

主题: Re: How to limit the number of rows to export data when using sqoopto export data
from hdfs to oracle?



Does Sqoop export work with Views? If not, you'll have to materialise the exact dataset you
want to sqoop using a CTAS.

regards
/Pelle


On Fri, Dec 1, 2017 at 11:08 AM, Attila Szabó <maugli@apache.org> wrote:
Hey, 


If you're trying to export from Hive into RDBMS I would suggest creating a Hive view and only
export the content of the view. Thus you could directly control the data quantity by the underlying
HiveQL query. 


My 2cents,
Attila 

On Dec 1, 2017 10:54 AM, "qq" <987626311@qq.com> wrote:
Hello:
      
      I have a question on the export of sqoop need your help, the problem is as follows:
      How to limit the number of rows that need to be exported when exporting data from hdfs
to oracle using sqoop?
      For example: hive data stored in the hdfs 100 lines, just want the first 10 lines of
data through sqoop exported to the oracle table, how to achieve through sqoop?
      I am looking forward to your reply!
      thinks.











 




-- 

Per Ullberg
Datavault Tech Lead
Odin (Uppsala)


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