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From "Hao Zhu (JIRA)" <j...@apache.org>
Subject [jira] [Created] (PIG-4485) Can Pig disable RandomSampleLoader when doing "Order by"
Date Fri, 27 Mar 2015 22:32:54 GMT
Hao Zhu created PIG-4485:
----------------------------

             Summary: Can Pig disable RandomSampleLoader when doing "Order by"
                 Key: PIG-4485
                 URL: https://issues.apache.org/jira/browse/PIG-4485
             Project: Pig
          Issue Type: Bug
    Affects Versions: 0.13.0
            Reporter: Hao Zhu
            Priority: Critical


When reading parquet files with "order by":
{code}
a = load '/xxx/xxx/parquet/xxx.parquet' using ParquetLoader();
b = order a by col1 ;
c = limit b 100 ;
dump c
{code}

Pig spawns a Sampler job always in the begining:
{code}
Job Stats (time in seconds):
JobId	Maps	Reduces	MaxMapTime	MinMapTIme	AvgMapTime	MedianMapTime	MaxReduceTime	MinReduceTime
AvgReduceTime	MedianReducetime	Alias	Feature	Outputs
job_1426804645147_1270	1	1	8	8	8	8	4	4	4	4	b	SAMPLER
job_1426804645147_1271	1	1	10	10	10	10	4	4	4	4	b	ORDER_BY,COMBINER
job_1426804645147_1272	1	1	2	2	2	2	4	4	4	4	b		hdfs:/tmp/temp-xxx/tmp-xxx,
{code}

The issue is when reading lots of files, the first sampler job can take a long time to finish.

The ask is:
1. Is the sampler job a must to implement "order by"?
2. If no, is there any way to disable RandomSampleLoader manually?

Thanks.



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