QiangCai opened a new pull request #3898: URL: https://github.com/apache/carbondata/pull/3898
### Why is this PR needed? 1. column comment is an empty string by default when adding a column 2. there are too many redundancy codes ### What changes were proposed in this PR? 1. change default column comment to null 2. re-factory code ### Does this PR introduce any user interface change? - No ### Is any new testcase added? - Yes ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org