GNU bug report logs - #16468
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From: Pádraig Brady <P <at> draigBrady.com>
To: Bernhard Voelker <mail <at> bernhard-voelker.de>
Cc: barry kesner <modockesner <at> gmail.com>, Eric Blake <eblake <at> redhat.com>, 16468 <at> debbugs.gnu.org
Subject: bug#16468: join
Date: Fri, 17 Jan 2014 02:21:33 +0000

On 01/17/2014 12:00 AM, Bernhard Voelker wrote:
> On 01/16/2014 07:10 PM, Eric Blake wrote:
>> On 01/16/2014 10:46 AM, barry kesner wrote:
>>>   How do you tell join this without resorting.  The files are huge!
>>
>> Unfortunately, there isn't any really good way, short of re-processing
>> the files to make the data appear sorted in the order join expects.
>> That said, it certainly appears that for your given data, you can write
>> a sed filter that can reprocess on a line-by-line basis, and feed that
>> into join, without the penalty of having to re-sort the entire file and
>> without having to have the processed file stored in your file system all
>> at once.  It also seems possible to write a post filter to get back to
>> the style of the line in the original file.  Here, extensions such as bash's
>>   join <(infilter file1) <(infilter file2) | outfilter
>> make it easier to type (where the trick is to now write the correct sed
>> scripts to serve as infilter and outfilter) than the alternative of
>> having to use named fifos for limiting yourself to just POSIX semantics.
> 
> Hum, isn't such number conversion filtering exactly what numfmt
> wasn't designed for?  But wait ...
> 
>   $ numfmt --field 1 --format='%020f' < f2
>               99980081    1
>              100002129   1
>              100002136   2
>              100002162   3
> 
> ... it doesn't support leading zeros, unfortunately. ;-/
> Wouldn't this be a nice enhancement?

Yes it really should support standard formatting directives.
leading zeros, precision in the format, etc.

thanks,
Pádraig.

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