maria-developers team mailing list archive

[Sergey Petrunia <sergey@xxxxxxxxxxx>]

Hi Sergei,

> commit eb7d6304a2aa168e09d48f6884dadf8c9f868feb
> Author: Sergei Krivonos <sergei.krivonos@xxxxxxxxxxx>
> Date:   Mon Nov 15 01:37:04 2021 +0200
>
>    do not output empty subqueries in traces

This reads as if the trace can have an empty clause describing a subquery. This
is very confusing.
Actually, the patch removes potential empty "subqueries" arrays.

Do you have a testcase for this? 

I'm trying to find one with 

grep -rn -A1 '"subqueries"' mysql-test/{main,suite} 

and I can't.


> diff --git a/sql/sql_explain.cc b/sql/sql_explain.cc
> index 499b6dbc97a..9a9bf786d62 100644
> --- a/sql/sql_explain.cc
> +++ b/sql/sql_explain.cc
> @@ -25,6 +25,8 @@
>  #include "opt_range.h"
>  #include "sql_expression_cache.h"
>  
> +#include <algorithm>
> +
Is this needed?  It seems to work without it.

> + bool Explain_node::has_json_printable_connection_objects(Explain_query *query) const
> + {
> +   auto n= children.elements();
> +   if (n)
> +   {
> +     for (; n--;)
> +     {
Why such a convoluted loop inside an if statement?  
Can you make the code simpler by using 

 for (n=0; n < children.elements(); n++)
 {
   if (is_connection_printable_in_json(children.at(i)->connection_type))
     return true;
 }
 return false;

?

> +       auto node= query->get_node(children.at(n));
> +       /* Derived tables are printed inside Explain_table_access objects */
> +
> +       if (!is_connection_printable_in_json(node->connection_type))
> +         continue;
> +
> +       return true;
> +     }
> +   }
> +   return false;
> + }

BR
 Sergei
-- 
Sergei Petrunia, Software Developer
MariaDB Corporation | Skype: sergefp | Blog: http://petrunia.net