[jira] Commented: (HADOOP-4927) Part files on the output filesystem are created irrespective of whether the corresponding task has anything to write there

["Doug Cutting (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HADOOP-4927?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12666231#action_12666231 ] 

Doug Cutting commented on HADOOP-4927:
--------------------------------------

The class might better be called LazyRecordWriter, I'd prefer that this we used no wrapper when lazy output creation is disabled, and we should add a static method to access the config property.  So, putting these together, we might have a method that looks like:

{code}
static RecordWriter ReduceTask#createRecordWriter(JobConf job, ...) {
  if (ReduceTask.useLazyOutputCreation(job)) {
    return new LazyRecordWriter(...);
  } else {
    return ...;
}
{code}

> Part files on the output filesystem are created irrespective of whether the corresponding task has anything to write there
> --------------------------------------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-4927
>                 URL: https://issues.apache.org/jira/browse/HADOOP-4927
>             Project: Hadoop Core
>          Issue Type: New Feature
>          Components: mapred
>            Reporter: Devaraj Das
>            Assignee: Jothi Padmanabhan
>             Fix For: 0.21.0
>
>         Attachments: hadoop-4927.patch
>
>
> When OutputFormat.getRecordWriter is invoked, a part file is created on the output filesystem. But the created RecordWriter is not used until the OutputCollector.collect call is made by the task (user's code). This results in empty part files even if the OutputCollector.collect is never invoked by the corresponding tasks.

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