From: Dmitry Lenev
Date: September 20 2010 6:53am
Subject: Re: bzr commit into mysql-5.1-bugteam branch (Li-Bing.Song:3489)
	Bug#56226
List-Archive: http://lists.mysql.com/commits/118557
Message-Id: <20100920065328.GA4045@mockturtle>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii

Hello Li-Bing!

Here are my comment about your patch:

* Li-Bing.Song@stripped <Li-Bing.Song@stripped> [10/09/16 13:40]:
> #At file:///home/anders/work/bzrwork1/wt2/mysql-5.1-bugteam/ based on revid:mattias.jonsson@stripped
> 
>  3489 Li-Bing.Song@stripped	2010-09-16
>       Bug#56226  Table map set to 0 after altering MyISAM table
>       
>       A MyISAM table's table_map_id will always be reset to 0 after altered
>       only its metadata. 0 is a valid value of table_map_id. But the problem will
>       cause that more than one tables have the same table_map_id 0. If more than
>       one tables which's table_map_id are 0 are updated in one statement, the update
>       of these different tables will be write into only one rows event. It will
>       cause slave server to crash. 
>       
>       After this patch, table_map_id always be refreshed as a correct value after
>       altered only its metadata.

...

> === modified file 'sql/sql_base.cc'
> --- a/sql/sql_base.cc	2010-07-20 18:07:36 +0000
> +++ b/sql/sql_base.cc	2010-09-16 09:35:41 +0000
> @@ -662,6 +662,7 @@ void close_handle_and_leave_table_as_loc
>      share->set_table_cache_key(key_buff, old_share->table_cache_key.str,
>                                 old_share->table_cache_key.length);
>      share->tmp_table= INTERNAL_TMP_TABLE;       // for intern_close_table()
> +    share->table_map_id= ~0UL;
>    }
>  
>    /*
> @@ -3082,7 +3083,8 @@ bool reopen_table(TABLE *table)
>    tmp.maybe_null=	table->maybe_null;
>    tmp.status=		table->status;
>  
> -  tmp.s->table_map_id=  table->s->table_map_id;
> +  if (table->s->table_map_id != ~0UL)
> +    tmp.s->table_map_id=  table->s->table_map_id;
>  

I don't think that there is a situation when it makes sense to
inherit table_map_id from old version of share here.
Especially since, AFAIU, shares for TABLE objects for which 
reopen_table() is called are always dummy and not a real shares.

So I think it makes sense simply to remove this line and keep 
close_handle_and_leave_table_as_lock() as is.

-- 
Dmitry Lenev, Software Developer
Oracle Development SPB/MySQL, www.mysql.com

Are you MySQL certified?  http://www.mysql.com/certification