Re: [COMMITTERS] pgsql: Teach tuplesort.c about "top N" sorting, in which only the first

On May 9, 2007, at 11:01 AM, Magnus Hagander wrote:
> On Wed, May 09, 2007 at 10:55:12AM -0500, Jim Nasby wrote:
>> On May 8, 2007, at 2:24 PM, Magnus Hagander wrote:
>>> Speaking of which, it might be interesting to actually show these
>>> values
>>> in the stats collector. I was thinking three cols for each database
>>> (probably the best level?) that counts each of those three
>>> counters. If
>>> you have a lot of sorts (percentage-wise) spilling to disk, it is
>>> often
>>> something you want to investigate, so exposing it that way seems
>>> like a
>>> good thing.
>>
>> What 3 columns? In-memory sorts, on-disk sorts, and on-disk size?
>> (Sum of how much spilled to disk).
>
> I was thinking in-mem sorts, on-disk sorts, limited-by-LIMIT sorts
> (that
> would be the new feature..)

It would also be useful to know how much got spilled to disk. If it's
a large amount per sort, then there's probably not much you could do,
but if it's just a tad over available memory per-sort...
--
Jim Nasby jim(at)nasby(dot)net
EnterpriseDB http://enterprisedb.com 512.569.9461 (cell)