At 12:14 PM 1/12/2009, Dan Nelson wrote:
>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
Why would delay_key_writes require a table rebuild? It's not
modifying the data. Reloading tens of millions of rows for several hours
seems to be a waste of time.