On 02/22/2011 12:06 PM, Tom Lane wrote: > Reid Thompson <Reid.Thompson@xxxxxxxx> writes: >> What am I missing that causes this to resort to sorting on disk? > > The in-memory space required to sort N tuples can be significantly > larger than the on-disk space, because the latter representation is > optimized to be small and the in-memory representation not so much. > I haven't seen a 3X differential before, but it's not outside the realm > of reason, especially for narrow rows like these where it's all about > the overhead. I suspect if you crank work_mem up still more, you'll see > it switch over. It flips to on-disk sort when the in-memory > representation exceeds the limit ... > > regards, tom lane ahh, ok; the underlying cpn.value table is 11 GB so I understand how even slightly less optimized representation could be significantly larger than ~300MB/900MB Thanks, reid -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
