Brian Dunning wrote:
> Hey all -
> I have a table with 12,000,000 records spread over about 6 years. I'm trying to
> delete all but the last 2 years, but no matter how small of a group I try to delete at a
> time, it keeps hanging up the server and I eventually have to restart MySQL. The table
> looks like this:
> `creation` timestamp NOT NULL default CURRENT_TIMESTAMP on update
> `lat` double NOT NULL default '0',
> `lon` double NOT NULL default '0',
> `referer` int(12) NOT NULL default '0',
> PRIMARY KEY (`referer`,`lat`,`lon`),
> KEY `creation` (`creation`,`referer`)
> And the query I've been trying looks like this:
> delete from tablename where `creation` < '2006-04-01 00:00:00'
> ...trying to do the oldest 1 month of records at a time. So am I just trying a really
> inefficient query? Is there a better way to do this?
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My idea is to create a new table with just the data you want to keep and
drop the old one. Every batch you delete must update the indexes on the
existing table. Creating a new,smaller, batch of data with a fresh set
of indexes should be much faster than incrementally deflating the
existing huge set of data.
Once the new table is created, use a RENAME TABLE to swap both table
names to put the new table into the old one's place and to give the old
table a name you can work with later.
MySQL Principle Technical Support Engineer
Oracle USA, Inc.
Office: Blountville, TN