GitHub user cloud-fan opened a pull request:
https://github.com/apache/spark/pull/18251
[SPARK-21033][SQL] fix the potential OOM in UnsafeExternalSorter
## What changes were proposed in this pull request?
In `UnsafeInMemorySorter`, one record may take 32 bytes: 1 `long` for
pointer, 1 `long` for key-prefix, and another 2 `long`s as the temporary buffer
for radix sort.
In `UnsafeExternalSorter`, we set the
`DEFAULT_NUM_ELEMENTS_FOR_SPILL_THRESHOLD` to be `1024 * 1024 * 1024 / 2`, and
hoping the max size of point array to be 8 GB. However this is wrong, `1024 *
1024 * 1024 / 2 * 32` is actually 16 GB, and if we grow the point array before
reach this limitation, we may hit the max-page-size error.
This PR fixes this by making `DEFAULT_NUM_ELEMENTS_FOR_SPILL_THRESHOLD` 2
times smaller, and adding a safe check in
`UnsafeExternalSorter.growPointerArrayIfNecessary` to avoid allocating a page
larger than max page size.
## How was this patch tested?
TODO
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/cloud-fan/spark sort
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/18251.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 #18251
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commit 93550f44397e79288fc94fb8bad60d271db5da58
Author: Wenchen Fan <[email protected]>
Date: 2017-06-09T08:39:28Z
fix the potential OOM in UnsafeExternalSorter
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