GitHub user davies opened a pull request:
https://github.com/apache/spark/pull/9846
[SPARK-11864] [SQL] Improve performance of max/min
This PR has the following optimization:
1) The greatest/least already does the null-check, so the `If` and `IsNull`
are not necessary.
2) In greatest/least, it should initialize the result using the first child
(removing one block).
3) For primitive types, the generated greater expression is too complicated
(`a > b ? 1 : (a < b) ? -1 : 0) > 0`), should be as simple as `a > b`
Combine these optimization, this could improve the performance of `ss_max`
query by 30%.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/davies/spark improve_max
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/9846.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 #9846
----
commit 3a23581dd058b1d7955ddc3c16f4c4dd6e4da308
Author: Davies Liu <[email protected]>
Date: 2015-11-19T21:38:28Z
improve max/min
commit 71411199cf27043cafd03ec4ff5ca80d817c56b6
Author: Davies Liu <[email protected]>
Date: 2015-11-19T21:39:21Z
Revert "improve max/min"
This reverts commit 3a23581dd058b1d7955ddc3c16f4c4dd6e4da308.
commit 7f7e33dc981b09d6983a3003bfdf86a7d4cd0fef
Author: Davies Liu <[email protected]>
Date: 2015-11-19T21:40:30Z
improve max/min
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