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Pig, mail # user - load union store


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Kris Coward 2011-01-28, 00:40
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Dmitriy Ryaboy 2011-01-28, 01:57
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Kris Coward 2011-01-28, 17:11
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Re: load union store
Ashutosh Chauhan 2011-01-28, 19:25
Howl is coming. This is one of the basic use cases for Howl.

1) You create a partitioned table in it. (In this case partitioned by date)
2) You add some partitions to your table. (In this case for each date,
new log files)
3) You query your table in Howl using Pig to do analysis.
4) Next day, you add new partition to Howl table.
5) Run your pig script either on newly created partition (by using
filters) or on full dataset.
6) Repeat.

Note that all the path munging, schema management, load-union-store is
gone. You are relieved of all that. Howl presents you with a table
like abstraction for your Hadoop datasets.

More info: http://wiki.apache.org/pig/Howl

Ashutosh

On Fri, Jan 28, 2011 at 09:11, Kris Coward <[EMAIL PROTECTED]> wrote:
>
> I want to flatten things at least a little, since I'm looking for
> year-long trends in logfiles that are rotated hourly (and loading the
> data back out of 8760 distinct directories isn't my idea of a good
> time).
>
> Any reason that moving/renaming the part-nnnn files wouldn't work?
>
> Thanks,
> Kris
>
> On Thu, Jan 27, 2011 at 05:57:32PM -0800, Dmitriy Ryaboy wrote:
>> Kris,
>> As logs accumulate over time the union will get slow since you have to read
>> all the data off disk and write it back to disk.
>>
>> Why not just have a hierarchy in your cleaned log directory? You can do
>> something like
>> define newdir `date +%s`
>>
>> store newclean into 'cleaned_files/$newdir/'
>>
>>
>> then to load all logs you can just load 'cleaned_files'
>>
>> you can also format the date output differently and wind up with your
>> cleaned files nicely organized by year/month/day/hour/ ...
>>
>> D
>>
>> On Thu, Jan 27, 2011 at 4:40 PM, Kris Coward <[EMAIL PROTECTED]> wrote:
>>
>> > Hi all,
>> >
>> > I'm writing a bit of code to grab some logfiles, parse them, and run some
>> > sanity checks on them (before subjecting them to further analysis).
>> > Naturally, logfiles being logfiles, they accumulate, and I was wondering
>> > how efficiently pig would handle a request to add recently accumulated
>> > log data to a bit of logfile that's already been started.
>> >
>> > In particular, two approaches that I'm contemplating are
>> >
>> > raw = LOAD 'logfile' ...
>> > -- snipped parsing/cleaning steps producing a relation with alias
>> > "cleanfile"
>> > oldclean = LOAD 'existing_log';
>> > newclean = UNION oldclean, cleanfile;
>> > STORE newclean INTO 'tmp_log';
>> > rm existing_log;
>> > mv tmp_log existing_log;
>> >
>> > ...ALTERNATELY...
>> >
>> > raw = LOAD 'logfile' ...
>> > -- snipped parsing/cleaning steps producing a relation with alias
>> > "cleanfile"
>> > STORE cleanfile INTO 'tmp_log';
>> >
>> > followed by renumbering all the part files in tmp_log and copying them
>> > to existing_log.
>> >
>> > Is pig clever enough to handle the first set of instructions reasonably
>> > efficiently (and if not, are there any gotchas I'd have to watch out for
>> > with the second approach, e.g. a catalogue file that'd have to be edited
>> > when the new parts are added).
>> >
>> > Thanks,
>> > Kris
>> >
>> > --
>> > Kris Coward                                     http://unripe.melon.org/
>> > GPG Fingerprint: 2BF3 957D 310A FEEC 4733  830E 21A4 05C7 1FEB 12B3
>
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Dmitriy Ryaboy 2011-01-28, 21:27
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Kris Coward 2011-01-28, 21:53
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Dmitriy Ryaboy 2011-01-28, 22:05