GitHub user mateiz opened a pull request:
https://github.com/apache/spark/pull/986
SPARK-2043: ExternalAppendOnlyMap doesn't always find matching keys
The current implementation reads one key with the next hash code as it
finishes reading the keys with the current hash code, which may cause it to
miss some matches of the next key. This can cause operations like join to give
the wrong result when reduce tasks spill to disk and there are hash collisions,
as values won't be matched together. This PR fixes it by not reading in that
next key, using a peeking iterator instead.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/mateiz/spark spark-2043
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/986.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #986
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commit 892debbbc9f00c3e76eecf8bcc9bc91734c57b21
Author: Matei Zaharia <[email protected]>
Date: 2014-06-05T22:01:55Z
SPARK-2043: don't read a key with the next hash code in
ExternalAppendOnlyMap, instead use a buffered iterator to only read
values with the current hash code.
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