GitHub user kiszk opened a pull request:
https://github.com/apache/spark/pull/13680
[SPARK-15962][SQL] Introduce additonal implementation with a dense format
for UnsafeArrayData
## What changes were proposed in this pull request?
This PR introduces two implementations for ```UnsafeArrayData```. One is an
sparse array ```UnsafeArrayDataSparse``` that is the original format of
```UnsafeArrayData```. The other is a dense array ```UnsafeArrayDataDense```
that is a new format of ```UnsafeArrayData```.
```UnsafeArrayDataSparse``` accepts ```null``` value in each entry of an
array. However, it increases memory footprint (e.g. 2x for an integer array)
due to existence of [```offsets```
area](https://github.com/apache/spark/blob/43b149fb885a27f9467aab28e5195f6f03aadcf0/sql/catalyst/src/main/java/org/apache/spark/sql/catalyst/expressions/UnsafeArrayData.java#L35).
In some cases (e.g. an unsafe array is created from an primitive array by a
method ```fromPrimitiveArray```, we know there is no ```null``` value in an
array. ```UnsafeArrayDataDense``` can reduce memory footprint since it does not
have ```offsets``` area.
## How was this patch tested?
Tested by existing unit tests
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/kiszk/spark SPARK-15962
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/13680.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 #13680
----
commit 2b15523ddf0c8b8387302611d564fcc2de239af5
Author: Kazuaki Ishizaki <ishiz...@jp.ibm.com>
Date: 2016-06-14T19:46:29Z
add two implementations (sparse and dense) for UnsafeArrayData
commit 639b32d91cee1572e1146f325c40e158a8158ce5
Author: Kazuaki Ishizaki <ishiz...@jp.ibm.com>
Date: 2016-06-15T06:19:18Z
fix failures of testsuite
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