GitHub user dongjoon-hyun opened a pull request:
https://github.com/apache/spark/pull/12590
[SPARK-14830][SQL] Add RemoveRepetitionFromGroupExpressions optimizer.
## What changes were proposed in this pull request?
This PR aims to optimize GroupExpressions by removing repeating expressions.
`RemoveRepetitionFromGroupExpressions` is added.
**Before**
```scala
scala> sql("select a from (select explode(array(1,2)) a) T group by a, a,
a").explain()
== Physical Plan ==
WholeStageCodegen
: +- TungstenAggregate(key=[a#5,a#5,a#5], functions=[], output=[a#5])
: +- INPUT
+- Exchange hashpartitioning(a#5, a#5, a#5, 200), None
+- WholeStageCodegen
: +- TungstenAggregate(key=[a#5,a#5,a#5], functions=[],
output=[a#5,a#5,a#5])
: +- INPUT
+- Generate explode([1,2]), false, false, [a#5]
+- Scan OneRowRelation[]
```
**After**
```scala
scala> sql("select a from (select explode(array(1,2)) a) T group by a, a,
a").explain()
== Physical Plan ==
WholeStageCodegen
: +- TungstenAggregate(key=[a#5], functions=[], output=[a#5])
: +- INPUT
+- Exchange hashpartitioning(a#5, 200), None
+- WholeStageCodegen
: +- TungstenAggregate(key=[a#5], functions=[], output=[a#5])
: +- INPUT
+- Generate explode([1,2]), false, false, [a#5]
+- Scan OneRowRelation[]
```
## How was this patch tested?
Pass the Jenkins tests (with a new testcase)
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/dongjoon-hyun/spark SPARK-14830
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/12590.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 #12590
----
commit 75b8f7353454cbe6aa8dafa070f51c90d0f430e5
Author: Dongjoon Hyun <[email protected]>
Date: 2016-04-22T00:08:32Z
[SPARK-14830][SQL] Add RemoveRepetitionFromGroupExpressions optimizer.
----
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