From: Dan Nelson
Date: January 12 2009 6:14pm
Subject: Re: Why does changing a table property rebuild the table?
List-Archive: http://lists.mysql.com/mysql/215885
Message-Id: <20090112181430.GB57874@dan.emsphone.com>
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In the last episode (Jan 12), mos said:
> I'm using MySQL 5.1 and if I execute:
> 
> alter table mytable delay_key_write=1;
> 
> it takes about an hour to rebuild the table. Why? As far as I know it
> is not changing the table structure. So why does it have to make a
> copy of the table and reload all the data?

Mysql plays it safe and assumes that any table modification requires a
full rebuild.  5.1 knows that certain settings don't require a full
rebuild, but delay_key_writes isn't one of them (and some that are
marked as fast shouldn't be - see
http://bugs.mysql.com/bug.php?id=39372 ).

-- 
	Dan Nelson
	dnelson@stripped