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From "Daniel Dai (Commented) (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (PIG-2462) getWrappedSplit is incorrectly returning the first split instead of the current split.
Date Tue, 10 Jan 2012 19:00:42 GMT

    [ https://issues.apache.org/jira/browse/PIG-2462?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13183478#comment-13183478
] 

Daniel Dai commented on PIG-2462:
---------------------------------

Yes, you are right. That's why you pass index from PigRecordReader to PigSplit. Your approach
looks right. Except for the name "splitIndex", we usually refer it to the index of PigSplit
itself, not the index of InputSplit inside PigSplit. It's better to use "idx" to make it less
confused. 
                
> getWrappedSplit is incorrectly returning the first split instead of the current split.
> --------------------------------------------------------------------------------------
>
>                 Key: PIG-2462
>                 URL: https://issues.apache.org/jira/browse/PIG-2462
>             Project: Pig
>          Issue Type: Bug
>    Affects Versions: 0.9.1, 0.11
>            Reporter: Alex Rovner
>             Fix For: 0.11
>
>         Attachments: splitsfix.patch
>
>
> If your loader needs information regarding what file is currently is being read (lets
say for schema information), currently provides this ability by calling prepareToRead every
time we read a new split. This is critical for ComibinedInputFormat as each mapper can read
more then one file. In order for the load function to know what file we are currently reading,
it should call getWrappedSplit() to get that information. How ever, getWrappedSplit always
returns the first split in the list. Code from PigSplit.java:
>     /**
>      * This methods returns the actual InputSplit (as returned by the 
>      * {@link InputFormat}) which this class is wrapping.
>      * @return the wrappedSplit
>      */
>     public InputSplit getWrappedSplit() {
>         return wrappedSplits[0];
>     }
> Furthermore, in PigRecordReader.java the splitIndex is never incremented when changing
from split to split. So in fact, even if getWrappedSplit() wold be changed to return wrappedSplits[splitIndex];
it would still return the incorrect index. 
> This can be fixed by changing PigRecordReader to increment PigSplit.splitIndex everytime
the split chagnes in the following code:
>     /**
>      * Get the record reader for the next chunk in this CombineFileSplit.
>      */
>     protected boolean initNextRecordReader() throws IOException, InterruptedException
{
>         if (curReader != null) {
>             curReader.close();
>             curReader = null;
>             if (idx > 0) {
>                 progress += pigSplit.getLength(idx-1);    // done processing so far
>             }
>         }
>         // if all chunks have been processed, nothing more to do.
>         if (idx == pigSplit.getNumPaths()) {
>             return false;
>         }
>         // get a record reader for the idx-th chunk
>         try {
>           
>             curReader =  inputformat.createRecordReader(pigSplit.getWrappedSplit(idx),
context);
>             LOG.info("Current split being processed "+pigSplit.getWrappedSplit(idx));
>             if (idx > 0) {
>                 // initialize() for the first RecordReader will be called by MapTask;
>                 // we're responsible for initializing subsequent RecordReaders.
>                 curReader.initialize(pigSplit.getWrappedSplit(idx), context);
>                 pigSplit.get
>                 loadfunc.prepareToRead(curReader, pigSplit);
>             }
>         } catch (Exception e) {
>             throw new RuntimeException (e);
>         }
>         idx++;
>         return true;
>     }
> }

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