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From "Travis Crawford (Updated) (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (PIG-2573) Automagically setting parallelism based on input file size does not work with HCatalog
Date Sun, 11 Mar 2012 05:18:16 GMT

     [ https://issues.apache.org/jira/browse/PIG-2573?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Travis Crawford updated PIG-2573:
---------------------------------

    Status: Patch Available  (was: Open)
    
> Automagically setting parallelism based on input file size does not work with HCatalog
> --------------------------------------------------------------------------------------
>
>                 Key: PIG-2573
>                 URL: https://issues.apache.org/jira/browse/PIG-2573
>             Project: Pig
>          Issue Type: Bug
>            Reporter: Travis Crawford
>            Assignee: Travis Crawford
>         Attachments: PIG-2573_get_size_from_stats_if_possible.diff, PIG-2573_move_getinputbytes_to_loadfunc.diff
>
>
> PIG-2334 was helpful in understanding this issue. Short version is input file size is
only computed if the path begins with a whitelisted prefix, currently:
> * /
> * hdfs:
> * file:
> * s3n:
> As HCatalog locations use the form {{dbname.tablename}} the input file size is not computed,
and the size-based parallelism optimization breaks.
> DETAILS:
> I discovered this issue comparing two runs on the same script, one loading regular HDFS
paths, and one with HCatalog db.table names. I just happened to notice the "Setting number
of reducers" line difference.
> {code:title=Loading HDFS files reducers is set to 99}
> 2012-03-08 01:33:56,522 [main] INFO  org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.JobControlCompiler
- BytesPerReducer=1000000000 maxReducers=999 totalInputFileSize=98406674162
> 2012-03-08 01:33:56,522 [main] INFO  org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.JobControlCompiler
- Neither PARALLEL nor default parallelism is set for this job. Setting number of reducers
to 99
> {code}
> {code:title=Loading with an HCatalog db.table name}
> 2012-03-08 01:06:02,283 [main] INFO  org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.JobControlCompiler
- BytesPerReducer=1000000000 maxReducers=999 totalInputFileSize=0
> 2012-03-08 01:06:02,283 [main] INFO  org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.JobControlCompiler
- Neither PARALLEL nor default parallelism is set for this job. Setting number of reducers
to 1
> {code}
> Possible fix: Pig should just ask the loader for the size of its inputs rather than special-casing
certain location types.

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