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.
Performance bug, no additional test added.
Author: Qifan Pu <qifan.pu@gmail.com>
Closes#14337 from ooq/SPARK-16699.
(cherry picked from commit d226dce12b)
Signed-off-by: Reynold Xin <rxin@databricks.com>
468a3c3ac5