GitHub user davies opened a pull request:
https://github.com/apache/spark/pull/9120
[SPARK-11111] [SQL] fast null-safe join
Currently, we use CartesianProduct for join with null-safe-equal condition.
```
scala> sqlContext.sql("select * from t a join t b on (a.i <=> b.i)").explain
== Physical Plan ==
TungstenProject [i#2,j#3,i#7,j#8]
Filter (i#2 <=> i#7)
CartesianProduct
LocalTableScan [i#2,j#3], [[1,1]]
LocalTableScan [i#7,j#8], [[1,1]]
```
Actually, we can have an equal-join condition as `coalesce(i, default) =
coalesce(b.i, default)`, then an partitioned join algorithm could be used.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/davies/spark null_safe
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/9120.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 #9120
----
commit 949c8c379cd580679ef71820f7d26d8c4a987b83
Author: Davies Liu <dav...@databricks.com>
Date: 2015-10-14T20:09:38Z
extract joining key for null safe join
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