[NSE-1108] allow to use different cases in column names

[zhouyuan]

What changes were proposed in this pull request?

This patch fixes the different cases in column names by converting them to lower case

How was this patch tested?

pass jenkins

[github-actions]

Thanks for opening a pull request!

Could you open an issue for this pull request on Github Issues?

https://github.com/oap-project/native-sql-engine/issues

Then could you also rename commit message and pull request title in the following format?

[NSE-${ISSUES_ID}] ${detailed message}

See also:

• Other pull requests

[github-actions]

#1108

[zhouyuan]

note: this fix relies on lower case table schema, a better solution would be switching to the boundreference:
https://github.com/apache/spark/blob/master/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/BoundAttribute.scala#L69