---------- Forwarded message ---------
From: Jeeukrishnan Kayshyap. <jeeukrishnan.181it220@nitk.edu.in>
Date: Thu, 26 Mar 2020, 2:58 pm
Subject: Re: [Maria-developers] Regarding GSoc :ADD FULL OUTER JOIN
To: Oleksandr Byelkin <sanja@montyprogram.com>, <maria-developers@lists.launchpad.net>


Hi , in this reply what does parsing mean??The parsing done by parser right??Or "parsing some parts of query union" means something else in this reply??

So, if this reply means parsing of UNION will make it simple ,how it is going to do so?Can I get some insights about this ?Actually I have a course in my academics "Automata and Compiler Design" , in that I study about parser.So I have a basic idea about parser and its works and its production rules such as top down and bottom-up.But I cannot think how it can make a query like UNION simpler.I study the parser code in the file sql_yacc.yy also which begins from line 13448 where the tokens are in order of insert ,replace etc.But still not able to think how it can reduce complexity???

Or did I interpret the reply wrong way??Is it so??

Please guide me about this.

On Wed, Mar 25, 2020 at 1:06 PM Oleksandr Byelkin <sanja@montyprogram.com> wrote:
Am 24.03.20 um 09:35 schrieb Jeeukrishnan Kayshyap.:
> 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.

I discussed it with Igor and we conclude that after all if use parsing
some parts of the query UNION will be simplest way.

>
> 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.
>
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