Revision a406473a525285888dbc29503443173df1d1c490 authored by Wang Gengliang on 27 September 2017, 15:40:31 UTC, committed by Herman van Hovell on 27 September 2017, 15:40:31 UTC
Back port https://github.com/apache/spark/pull/19362 to branch-2.2
## 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
Author: Wang Gengliang <ltnwgl@gmail.com>
Closes #19366 from gengliangwang/branch-2.2.
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