From: Roy Lyseng
Date: May 12 2009 6:51pm
Subject: Re: MySQL Reengineering Project
List-Archive: http://lists.mysql.com/internals/36647
Message-Id: <4A09C516.5080002@sun.com>
MIME-Version: 1.0
Content-Type: text/plain; CHARSET=US-ASCII; format=flowed
Content-Transfer-Encoding: 7BIT



Sergei Golubchik wrote:
> Hi, Jay!
> 
> On May 12, Jay Pipes wrote:
>>> However, do you know of any other interfaces that work this way? I am
>>> personally not aware of any other, but then I don't know every corner
>>> of the code like Serg does. :)
>> "External" interfaces?  See all the plugin "interfaces".  There's no 
>> enforcement of types really at all. Just passing void *'s around.
> 
> Where ? Plugin interfaces don't pass void* around much.
> They do it in two places (that I remember out of my head):
>   - init() function. Brian added that to pass handlerton down.
>     it is ignored by any clean plugin API and should've been done
>     differently for storage engines and I_S tables.
> 
>   - MYSQL_THD is defined as void*, which is fine as it's an opaque
>     pointer, plugins are never expected to look inside to cast it to
>     anything.
> 
>> As for the internal interfaces, I would suggest cleaning up the class 
>> interfaces of THD, JOIN, and other major classes to enforce public 
>> accessors and getters, protecting private member variables behind a clean 
>> API.  This would, eventually, make some of these classes semi-usable in 
>> public interfaces.
> 
> We don't have public interfaces for them (besides few thd_* accessors
> functions) in plugin.h. And doubt that we want to have them.
> We're working on new APIs to access these objects, instead of putting
> lipstick on old ones.
> 
>> Another thing to think about in your refactoring efforts is detaching the 
>> THD from its current inheritance from Statement, Query_arena and ilink.  
>> Without doing this, and using encapsulation so that a THD can have multiple 
>> Statements, it will be very difficult to work on any future parallelization 
>> efforts.
> 
> You mean, a Statement can have multiple THDs, I suppose :)

...or many threads (not THDs) per Statement if you ever asked me.

Thanks,
Roy