This week was more productive than the last one. Zulip messages helped to
extend parser for INSERT...SELECT...RETURNING. I created SELECT_LEX ::
returning_list and swapped it with SELECT_LEX :: item_list. I have also added test cases and result for the same. Feedback of GDoc and zulip messages helped in understanding the code better. I have started implementing INSERT...RETURNING. I am able to check whether there is result set in the query. But during result->send_result_set_metadata() server crashes and I get segmentation fault. I am trying to fix it. 

Here is the link to my last commit of code and test cases

code: https://github.com/MariaDB/server/commit/d06f21b84cc65424a795c21cc3fee5546eec0a54  

Test case: https://github.com/MariaDB/server/commit/280a885f1563594678141a360305a253b48f72d8

Result: https://github.com/MariaDB/server/commit/218d81b86d941a874cfac9123d7aeb141e01f110

Regards,

Rucha Deodhar