Re: WITHIN GROUP patch

On Sun, Jan 5, 2014 at 12:00 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
>
> Looking at this example makes me wonder if it wouldn't be worthwhile to
> provide a way to reset and re-use a tuplesort object, instead of redoing
> all the lookup work involved. Or maybe just find a way to cache the
> catalog lookups that are happening inside tuplesort_begin_datum, which are
> about 50% of that function's cost it looks like. We're paying this same
> kind of price for repeated tuplesort setup in the existing nodeAgg code,
> if we have an aggregate with ORDER BY or DISTINCT in a grouped query with
> many groups.
>
>
This sounds very similar to:
http://www.postgresql.org/message-id/CAApHDvrbq348M8dYj-7O4VaE5PS9ZoQ_34rGvaaN1QYXL2SP_A@mail.gmail.com
A reset function was added in the next patch which improved performance in
my test case by about 5 times.

Perhaps they can make use of the same function.

Regards

David Rowley

> regards, tom lane
>
>
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