GitHub user gengliangwang opened a pull request:
https://github.com/apache/spark/pull/19362
[SPARK-22141][SQL] Propagate empty relation before checking Cartesian
products
## What changes were proposed in this pull request?
When inferring constraints from children, Join's condition can be
simplified as None.
For example,
```
val testRelation = LocalRelation('a.int)
val x = testRelation.as("x")
val y = testRelation.where($"a" === 2 && !($"a" === 2)).as("y")
x.join.where($"x.a" === $"y.a")
```
The plan will become
```
Join Inner
:- LocalRelation <empty>, [a#23]
+- LocalRelation <empty>, [a#224]
```
And the Cartesian products check will throw exception for above plan.
Propagate empty relation before checking Cartesian products, and the issue
is resolved.
## How was this patch tested?
Unit test
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/gengliangwang/spark MoveCheckCartesianProducts
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/19362.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 #19362
----
commit 0f25a074821481e89a256824b40acf78a06841e5
Author: Wang Gengliang <[email protected]>
Date: 2017-09-27T07:51:08Z
propagate empty relation before checking Cartesian products
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