On Tue, Sep 6, 2016 at 10:36 PM, Peter Geoghegan <pg@heroku.com> wrote:
> Well, maybe, but the whole idea behind replacement_sort_tuples (by
> which I mean the continued occasional use of replacement selection by
> Postgres) was that we hope to avoid a merge step *entirely*. This new
> merge shift down heap patch could make the merge step so cheap as to
> be next to free anyway (in the even of presorted input)
I mean: Cheaper than just processing the tuples to return to caller
without comparisons/merging (within the TSS_SORTEDONTAPE path). I do
not mean free in an absolute sense, of course.
--
Peter Geoghegan