GitHub user cloud-fan opened a pull request:
https://github.com/apache/spark/pull/13425
[SPARK-15441][SQL] support null object in Dataset outer-join
## What changes were proposed in this pull request?
Currently we can't encoder top level null object into internal row, as
Spark SQL doesn't allow row to be null, only its columns can be null.
This is not a problem before, as we assume the input object is never null.
However, for outer join, we do need the semantic of null object.
This PR fixes this problem by making both join side produce a single
column, i.e. nest the logical plan output(by `CreateStruct`), so that we have
an extra level to represent top level null obejct.
## How was this patch tested?
new test in `DatasetSuite`
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/cloud-fan/spark outer-join2
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/13425.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 #13425
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commit 56cf8409733e2246647c1edf1a475c9e19d45c5f
Author: Wenchen Fan <wenc...@databricks.com>
Date: 2016-05-31T22:43:14Z
support null object in Dataset outer-join
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