Re: Parallel tuplesort (for parallel B-Tree index creation)

On Fri, Oct 7, 2016 at 5:47 PM, Peter Geoghegan <pg(at)heroku(dot)com> wrote:
> Work is still needed on:
>
> * Cost model. Should probably attempt to guess final index size, and
> derive calculation of number of workers from that. Also, I'm concerned
> that I haven't given enough thought to the low end, where with default
> settings most CREATE INDEX statements will use at least one parallel
> worker.
>
> * The whole way that I teach nbtsort.c to disallow catalog tables for
> parallel CREATE INDEX due to concerns about parallel safety is in need
> of expert review, preferably from Robert. It's complicated in a way
> that relies on things happening or not happening from a distance.
>
> * Heikki seems to want to change more about logtape.c, and its use of
> indirection blocks. That may evolve, but for now I can only target the
> master branch.
>
> * More extensive performance testing. I think that this V3 is probably
> the fastest version yet, what with Heikki's improvements, but I
> haven't really verified that.

While I haven't made progress on any of these open items, I should
still get a version out that applies cleanly on top of git tip --
commit b75f467b6eec0678452fd8d7f8d306e6df3a1076 caused the patch to
bitrot. I attach V4, which is a fairly mechanical rebase of V3, with
no notable behavioral changes or bug fixes.

--
Peter Geoghegan