GitHub user inouehrs opened a pull request:
https://github.com/apache/spark/pull/14000
[SPARK-16331] [SQL] Reduce code generation time
## What changes were proposed in this pull request?
During the code generation, a `LocalRelation` often has a huge `Vector`
object as `data`. In the simple example below, a `LocalRelation` has a Vector
with 1000000 elements of `UnsafeRow`.
```
val numRows = 1000000
val ds = (1 to numRows).toDS().persist()
benchmark.addCase("filter+reduce") { iter =>
ds.filter(a => (a & 1) == 0).reduce(_ + _)
}
```
At `TreeNode.transformChildren`, all elements of the vector is
unnecessarily iterated to check whether any children exist in the vector since
`Vector` is Traversable. This part significantly increases code generation time.
This patch avoids this overhead by checking the number of children before
iterating all elements; `LocalRelation` does not have children since it extends
`LeafNode`.
The performance of the above example
```
without this patch
Java HotSpot(TM) 64-Bit Server VM 1.8.0_91-b14 on Mac OS X 10.11.5
Intel(R) Core(TM) i5-5257U CPU @ 2.70GHz
compilationTime: Best/Avg Time(ms) Rate(M/s)
Per Row(ns) Relative
------------------------------------------------------------------------------------------------
filter+reduce 4426 / 4533 0.2
4426.0 1.0X
with this patch
compilationTime: Best/Avg Time(ms) Rate(M/s)
Per Row(ns) Relative
------------------------------------------------------------------------------------------------
filter+reduce 3117 / 3391 0.3
3116.6 1.0X
```
## How was this patch tested?
using existing unit tests
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/inouehrs/spark compilation-time-reduction
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/14000.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 #14000
----
commit 5afd079f38e9618c4b3cd8be33d73724844a7cfd
Author: Hiroshi Inoue <[email protected]>
Date: 2016-06-30T15:52:40Z
Merge branch 'apache/master'
commit 153e170fe5a478d04559d430f566478a6e48528f
Author: Hiroshi Inoue <[email protected]>
Date: 2016-06-30T17:25:24Z
add check of # children to avoid redundant iteration in transformChildren
----
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