GitHub user wzhfy opened a pull request:
https://github.com/apache/spark/pull/17668
[SPARK-20366] [SQL] Fix recursive join reordering: inside joins are not
reordered
## What changes were proposed in this pull request?
If a plan has multi-level successive joins, e.g.:
```
Join
/ \
Union t5
/ \
Join t4
/ \
Join t3
/ \
t1 t2
```
Currently we fail to reorder the inside joins, i.e. t1, t2, t3.
In join reorder, we use `OrderedJoin` to indicate a join has been ordered,
such that when transforming down the plan, these joins don't need to be
rerodered again.
But there's a problem in the definition of `OrderedJoin`:
The real join node is a parameter, but not a child. This breaks the
transform procedure because `mapChildren` applies transform on parameters which
should be children.
In this patch, we change `OrderedJoin` to a class having the same structure
as a join node.
## How was this patch tested?
Add a corresponding test case.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/wzhfy/spark recursiveReorder
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/17668.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 #17668
----
commit 522d2fae3d5e35cad96997da73ab4980fb816735
Author: wangzhenhua <[email protected]>
Date: 2017-04-17T13:20:01Z
support recursive reorder
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