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From Robin East <robin.e...@xense.co.uk>
Subject Re: How to update a file which is in HDFS
Date Fri, 05 Jul 2013 07:45:24 GMT
The API for 1.1.2 FileSystem seems to include append().
Robin 
On 5 Jul 2013, at 01:50, Mohammad Tariq <dontariq@gmail.com> wrote:

> The current stable release doesn't support append, not even through the API. If you really
want this you have to switch to hadoop 2.x.
> See this JIRA.
> 
> Warm Regards,
> Tariq
> cloudfront.blogspot.com
> 
> 
> On Fri, Jul 5, 2013 at 3:05 AM, John Lilley <john.lilley@redpoint.net> wrote:
> Manickam,
> 
>  
> 
> HDFS supports append; it is the command-line client that does not. 
> 
> You can write a Java application that opens an HDFS-based file for append, and use that
instead of the hadoop command line.
> 
> However, this doesn’t completely answer your original question: “How do I move only
the delta part”?  This can be more complex than simply doing an append.  Have records in
the original file changed in addition to new records becoming available?  If that is the case,
you will need to completely rewrite the file, as there is no overwriting of existing file
sections, even directly using HDFS.  There are clever strategies for working around this,
like splitting the file into multiple parts on HDFS so that the overwrite can proceed in parallel
on the cluster; however, that may be more work that you are looking for.  Even if the delta
is limited to new records, the problem may not be trivial.  How do you know which records
are new?  Are all of the new records a the end of the file?  Or can they be anywhere in the
file?  If the latter, you will need more complex logic.
> 
>  
> 
> John
> 
>  
> 
>  
> 
> From: Mohammad Tariq [mailto:dontariq@gmail.com] 
> Sent: Thursday, July 04, 2013 5:47 AM
> To: user@hadoop.apache.org
> Subject: Re: How to update a file which is in HDFS
> 
>  
> 
> Hello Manickam,
> 
>  
> 
>         Append is currently not possible.
> 
> 
> 
> Warm Regards,
> 
> Tariq
> 
> cloudfront.blogspot.com
> 
>  
> 
> On Thu, Jul 4, 2013 at 4:40 PM, Manickam P <manickam.p@outlook.com> wrote:
> 
> Hi,
> 
>  
> 
> I have moved my input file into the HDFS location in the cluster setup. 
> 
> Now i got a new set of file which has some new records along with the old one. 
> 
> I want to move the delta part alone into HDFS because it will take more time to move
the file from my local to HDFS location. 
> 
> Is it possible or do i need to move the entire file into HDFS again? 
> 
>  
> 
>  
> 
>  
> 
> Thanks,
> Manickam P
> 
>  
> 
> 


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