[SPARK-16699][SQL] Fix performance bug in hash aggregate on long string keys #14337
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LGTM pending jenkins. |
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Test build #62774 has finished for PR 14337 at commit
|
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Merging in master/2.0. |
asfgit
pushed a commit
that referenced
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Jul 25, 2016
…ng keys
## What changes were proposed in this pull request?
In the following code in `VectorizedHashMapGenerator.scala`:
```
def hashBytes(b: String): String = {
val hash = ctx.freshName("hash")
s"""
|int $result = 0;
|for (int i = 0; i < $b.length; i++) {
| ${genComputeHash(ctx, s"$b[i]", ByteType, hash)}
| $result = ($result ^ (0x9e3779b9)) + $hash + ($result << 6) + ($result >>> 2);
|}
""".stripMargin
}
```
when b=input.getBytes(), the current 2.0 code results in getBytes() being called n times, n being length of input. getBytes() involves memory copy is thus expensive and causes a performance degradation.
Fix is to evaluate getBytes() before the for loop.
## How was this patch tested?
Performance bug, no additional test added.
Author: Qifan Pu <qifan.pu@gmail.com>
Closes #14337 from ooq/SPARK-16699.
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@ooq next time please open a pull request against master branch rather than 2.0. Thanks. |
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What changes were proposed in this pull request?
In the following code in
VectorizedHashMapGenerator.scala:when b=input.getBytes(), the current 2.0 code results in getBytes() being called n times, n being length of input. getBytes() involves memory copy is thus expensive and causes a performance degradation.
Fix is to evaluate getBytes() before the for loop.
How was this patch tested?
Performance bug, no additional test added.