On Thu, Feb 23, 2012 at 11:11 AM, Andy Colson <a...@squeakycode.net> wrote:
> On 2/23/2012 12:05 PM, Shaun Thomas wrote: > >> On 02/23/2012 11:56 AM, Greg Spiegelberg wrote: >> >> I know there are perils in using ctid but with the LOCK it should be >>> safe. This transaction took perhaps 30 minutes and removed 100k rows >>> and once the table was VACUUM'd afterward it freed up close to 20 GB >>> on the file system. >>> >> >> It took *30 minutes* to delete 100k rows? And 100k rows were using 20GB? >> Is that off by an order of magnitude? >> >> Using the ctid is a cute trick, though. :) >> >> > And I'm not sure the LOCK is necessary, while googling for "delete from > table limit 10" I ran across this thread: > > http://archives.postgresql.**org/pgsql-hackers/2010-11/**msg02028.php<http://archives.postgresql.org/pgsql-hackers/2010-11/msg02028.php> > > They use it without locks. > > I used LOCK simply because if a VACUUM FULL x; slipped in between the SELECT and the DELETE the ctid's could conceivably change. -Greg
