GitHub user viirya opened a pull request: https://github.com/apache/spark/pull/14327
[SPARK-16686][SQL] Project shouldn't be pushed down through Sample if it has new output ## What changes were proposed in this pull request? We push down `Project` through `Sample` in `Optimizer`. However, if the projected columns produce new output, they will encounter whole data instead of sampled data. It will bring some inconsistency between original plan (Sample then Project) and optimized plan (Project then Sample). In the extreme case such as attached in the JIRA, if the projected column is an UDF which is supposed to not see the sampled out data, the result of UDF will be incorrect. We shouldn't push down Project through Sample if the Project brings new output. ## How was this patch tested? Jenkins tests. You can merge this pull request into a Git repository by running: $ git pull https://github.com/viirya/spark-1 fix-sample-pushdown Alternatively you can review and apply these changes as the patch at: https://github.com/apache/spark/pull/14327.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 #14327 ---- commit 9521a5aca87bead3dcfeabd7abe3468194984ea3 Author: Liang-Chi Hsieh <sim...@tw.ibm.com> Date: 2016-07-23T10:13:07Z Project shouldn't be pushed down through Sample if it has new output. ---- --- If your project is set up for it, you can reply to this email and have your reply appear on GitHub as well. If your project does not have this feature enabled and wishes so, or if the feature is enabled but not working, please contact infrastructure at infrastruct...@apache.org or file a JIRA ticket with INFRA. --- --------------------------------------------------------------------- To unsubscribe, e-mail: reviews-unsubscr...@spark.apache.org For additional commands, e-mail: reviews-h...@spark.apache.org