[NSE-1104] fix hashagg w/ empty string

[zhouyuan]

What changes were proposed in this pull request?

This patch fixes one case of hashagg wrong results over multiple columns
group by col_a, col_b

col_a	col_b
"ab"	"ab"
"a"	"bab"
"aba"	"b"
"abab"	""

The fix introduced a new is_empty field to tell whether some columns are empty string, which can fix the issue on last row

Signed-off-by: Yuan Zhou yuan.zhou@intel.com

How was this patch tested?

new unit tests

[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]

#1104