GitHub user yhuai opened a pull request:
https://github.com/apache/spark/pull/1735
[SQL] Set outputPartitioning of BroadcastHashJoin correctly.
I think we will not generate the plan triggering this bug at this moment.
But, let me explain it...
Right now, we are using `left.outputPartitioning` as the
`outputPartitioning` of a `BroadcastHashJoin`. We may have a wrong physical
plan for cases like...
```sql
SELECT l.key, count(*)
FROM (SELECT key, count(*) as cnt
FROM src
GROUP BY key) l // This is buildPlan
JOIN r // This is the streamedPlan
ON (l.cnt = r.value)
GROUP BY l.key
```
Let's say we have a `BroadcastHashJoin` on `l` and `r`. For this case, we
will pick `l`'s `outputPartitioning` for the `outputPartitioning`of the
`BroadcastHashJoin` on `l` and `r`. Also, because the last `GROUP BY` is using
`l.key` as the key, we will not introduce an `Exchange` for this aggregation.
However, `r`'s outputPartitioning may not match the required distribution of
the last `GROUP BY` and we fail to group data correctly.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/yhuai/spark BroadcastHashJoin
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/1735.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 #1735
----
commit 96d9cb3fa6963b5c8154da9b9c3ff9b780fa1456
Author: Yin Huai <[email protected]>
Date: 2014-08-02T05:43:35Z
Set outputPartitioning correctly.
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