GitHub user dongjoon-hyun opened a pull request:
https://github.com/apache/spark/pull/18257
[SPARK-21044][SPARK-21041][SQL] Add RemoveInvalidRange optimizer
## What changes were proposed in this pull request?
This PR aims to add an optimizer remove invalid `Range` operators from the
beginning. There are two cases of invalidity.
1. The `start` and `end` values are equal.
2. The sign of `step` does not match `start` and `end`'s increasing order.
With `wholeStageCodeGen` option, both cases generates unnecessary java
codes. More worse,
[SPARK-21041](https://issues.apache.org/jira/browse/SPARK-21041) reports that
the second case returns wrong result.
**BEFORE**
```
scala> spark.range(0,0,1).explain
== Physical Plan ==
*Range (0, 0, step=1, splits=8)
```
**AFTER**
```
scala> spark.range(0,0,1).explain
== Physical Plan ==
LocalTableScan <empty>, [id#0L]
```
## How was this patch tested?
Pass the Jenkins with newly added test cases.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/dongjoon-hyun/spark SPARK-21041
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/18257.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 #18257
----
commit 6ab9b6fb559ab11ac95078a1672672edf85efbac
Author: Dongjoon Hyun <[email protected]>
Date: 2017-06-10T01:45:23Z
[SPARK-21044][SPARK-21041][SQL] Add RemoveInvalidRange optimizer
**BEFORE**
```
scala> spark.range(0,0,1).explain
== Physical Plan ==
*Range (0, 0, step=1, splits=8)
```
**AFTER**
```
scala> spark.range(0,0,1).explain
== Physical Plan ==
LocalTableScan <empty>, [id#0L]
```
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