Hi ,I am a GSoC aspirant . I am trying to solve https://jira.mariadb.org/browse/MDEV-13648 .

Firstly , I discussed a new algorithm with Igor Babev sir , but it was wrong as it will create space problem.

Now , I am planning to add some code in Sql_yacc.yy :

/*full join*/ after the right join where /*full join */ will contain :

1.left join implementation (similar to the implementation of left join in sql_yacc.yy (line no. 11956-11950))

The result table will be in a temporary table ->tab1.

2.Use of right join doing the swapping of table (similar to right join in this part ;(line no. 11992-12030))

the result of this will be stored in another temporary table ->tab2

3.Union all clause:

implementation of union all clause to combine tab1 and tab2.

So , Oleksandr Byelkin sir replied to me that , addition of UNION will make it more complicated.it could be done with less effort than adding full UNION.

But at present I am not able to get any idea how to reduce the complexity or any kind of new idea to implement it . Please guide me in the right direction and help me to solve this issue.