apache/spark — pull request #2354 by marmbrus (2014-09-11 09:08:18+00:00)
Title: [SQL][WIP] Visualizing query plans with graphviz

Implicitly adds a method `.viz` to all trees that builds a png using graphviz.

For example:
```scala
sql(""""
SELECT a.value
FROM src a
JOIN srcpart b
WHERE a.key = b.key AND hr = 1""").queryExecution.executedPlan.viz
```

![queryplan7690500953161842945](https://cloud.githubusercontent.com/assets/527/4231604/16f7d7a8-3993-11e4-89c3-a918b2a0b3b1.png)