From: Roy Lyseng
Date: May 27 2011 2:21pm
Subject: Re: bzr commit into mysql-trunk branch (gleb.shchepa:3358) WL#4897
List-Archive: http://lists.mysql.com/commits/138341
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Hi Guilhem, Gleb,

A couple of comments on Guilhem's comments first.

>> + This method:
>> + a) allocates a select_send object (if no one pre-allocated available),
>> + b) calculates and sends whole EXPLAIN data.
>> +
>> + @returns
>> + @retval FALSE Ok
>> + @retval TRUE Error
>
> GB39 nowadays the coding style allows true/false too, it's up to you.

My preferred Doxygen documentation for return values is

@return false if successful, true if error

This is so common, and saves two lines without loss of information.

>
> GB75 this code above resembles what is done in execute_sqlcom_select() (if
> lex->describe is true), which is:
>
> thd->send_explain_fields(result);
> res= mysql_explain_union(thd, &thd->lex->unit, result);
> ...
> if (res)
> result->abort_result_set();
> else
> result->send_eof();
> Can we make execute_sqlcom_select() call explain_data_modification(), to
> avoid duplication?
> The creation of the warning (of EXPLAIN EXTENDED) can also move into
> explain_data_modification().

If this is done, explain_data_modification() must be renamed as a SELECT is not 
a data modification. My suggestion in that case would be 
explain_query_specification() (Query specification is the term used in the SQL 
standard for a SELECT block).

Thank,
Roy