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From "Rachit Soni (JIRA)" <>
Subject [jira] [Commented] (CRUNCH-373) Problem while Performing MapSide join with ImmutableBytesWritable/Text
Date Tue, 01 Apr 2014 19:08:17 GMT


Rachit Soni commented on CRUNCH-373:

I was able to reproduce the same issue if I use Text instead of ImmutableBytesWritable.

> Problem while Performing MapSide join with ImmutableBytesWritable/Text
> ----------------------------------------------------------------------
>                 Key: CRUNCH-373
>                 URL:
>             Project: Crunch
>          Issue Type: Bug
>          Components: Core
>            Reporter: Rachit Soni
>            Assignee: Josh Wills
>         Attachments:
> I have been having issues performing MapSide Join with ImmutableBytesWritable as the
join key and it always have only 1 value in the map created in the initialize method of MapSideJoinDoFn[1].
With the same set of data if I perform reduce side join it works perfectly fine giving me
the correct result.
> Additionally, I am making sure the map can be loaded in memory.
> The result in both the above cases are different.  When I dug up the code where Map side
join is being performed in MapSideDoFn [1] when the right side is taken in memory and converted
to map [2] all the keys get over written with the last key that is being updated on the map.
Seems like there it is referencing the same memory location each and every time and is not
cloning it properly. This only happens when I use ImmutableBytesWritable/Text, anything except
> ImmutableBytesWritable/Text works perfectly fine.
> It looks like SeqFileReaderFactory (which I believe implements the PTable under the hood
for writables) does indeed reuse keys/values [3] in much the same ways reducers do.  So, I
think in this code [4] it needs to clone the keys/values rather than just store them in a
> Also, I am attaching a test which I wrote to reproduce the issue. 
> [1]
> [2]
> [3]
> [4]

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