GitHub user clockfly opened a pull request:
https://github.com/apache/spark/pull/13306
[SPARK-12988][SQL] Can't drop top level columns that contain dots
## What changes were proposed in this pull request?
This PR is work based on @dilipbiswal's
https://github.com/apache/spa
Github user SparkQA commented on the pull request:
https://github.com/apache/spark/pull/13306#issuecomment-221726709
**[Test build #59303 has
started](https://amplab.cs.berkeley.edu/jenkins/job/SparkPullRequestBuilder/59303/consoleFull)**
for PR 13306 at commit
[`7966bb7`](https://gi
