Home | About | Sematext search-lucene.com search-hadoop.com
 Search Hadoop and all its subprojects:

Switch to Threaded View
Pig, mail # user - Loader for small files


Copy link to this message
-
Re: Loader for small files
David LaBarbera 2013-02-11, 20:38
What process creates the data in HDFS? You should be able to set the block size there and avoid the copy.

I would test the dfs.block.size on the copy and see if you get the mapper split you want before worrying about optimizing.

David

On Feb 11, 2013, at 2:10 PM, Something Something <[EMAIL PROTECTED]> wrote:

> David:  Your suggestion would add an additional step of copying data from
> one place to another.  Not bad, but not ideal.  Is there no way to avoid
> copying of data?
>
> BTW, we have tried changing the following options to no avail :(
>
> set pig.splitCombination false;
>
> & a few other 'dfs' options given below:
>
> mapreduce.min.split.size
> mapreduce.max.split.size
>
> Thanks.
>
> On Mon, Feb 11, 2013 at 10:29 AM, David LaBarbera <
> [EMAIL PROTECTED]> wrote:
>
>> You could store your data in smaller block sizes. Do something like
>> hadoop fs HADOOP_OPTS="-Ddfs.block.size=1048576
>> -Dfs.local.block.size=1048576" -cp /org-input /small-block-input
>> You might only need one of those parameters. You can verify the block size
>> with
>> hadoop fsck /small-block-input
>>
>> In your pig script, you'll probably need to set
>> pig.maxCombinedSplitSize
>> to something around the block size
>>
>> David
>>
>> On Feb 11, 2013, at 1:24 PM, Something Something <[EMAIL PROTECTED]>
>> wrote:
>>
>>> Sorry.. Moving 'hbase' mailing list to BCC 'cause this is not related to
>>> HBase.  Adding 'hadoop' user group.
>>>
>>> On Mon, Feb 11, 2013 at 10:22 AM, Something Something <
>>> [EMAIL PROTECTED]> wrote:
>>>
>>>> Hello,
>>>>
>>>> We are running into performance issues with Pig/Hadoop because our input
>>>> files are small.  Everything goes to only 1 Mapper.  To get around
>> this, we
>>>> are trying to use our own Loader like this:
>>>>
>>>> 1)  Extend PigStorage:
>>>>
>>>> public class SmallFileStorage extends PigStorage {
>>>>
>>>>   public SmallFileStorage(String delimiter) {
>>>>       super(delimiter);
>>>>   }
>>>>
>>>>   @Override
>>>>   public InputFormat getInputFormat() {
>>>>       return new NLineInputFormat();
>>>>   }
>>>> }
>>>>
>>>>
>>>>
>>>> 2)  Add command line argument to the Pig command as follows:
>>>>
>>>> -Dmapreduce.input.lineinputformat.linespermap=500000
>>>>
>>>>
>>>>
>>>> 3)  Use SmallFileStorage in the Pig script as follows:
>>>>
>>>> USING com.xxx.yyy.SmallFileStorage ('\t')
>>>>
>>>>
>>>> But this doesn't seem to work.  We still see that everything is going to
>>>> one mapper.  Before we spend any more time on this, I am wondering if
>> this
>>>> is a good approach – OR – if there's a better approach?  Please let me
>>>> know.  Thanks.
>>>>
>>>>
>>>>
>>
>>