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

On Sun, Sep 11, 2016 at 6:28 AM, Heikki Linnakangas <hlinnaka(at)iki(dot)fi> wrote:
> * I renamed "tuplesort_heap_siftup()" to "tuplesort_delete_top()". I realize
> that this is controversial, per the discussion on the "Is
> tuplesort_heap_siftup() a misnomer?" thread. However, now that we have a new
> function, "tuplesort_heap_replace_top()", which is exactly the same
> algorithm as the "delete_top()" algorithm, calling one of them "siftup"
> became just too confusing.

I feel pretty strongly that this was the correct decision. I would
have gone further, and removed any mention of "Sift up", but you can't
win them all.

> * Instead of "root_displace", I used the name "replace_top", and
> "delete_top" for the old siftup function. Because we use "top" to refer to
> memtuples[0] more commonly than "root", in the existing comments.

Fine by me.

> * I shared the code between the delete-top and replace-top. Delete-top now
> calls the replace-top function, with the last element of the heap. Both
> functions have the same signature, i.e. they both take the checkIndex
> argument. Peter's patch left that out for the "replace" function, on
> performance grounds, but if that's worthwhile, that seems like a separate
> optimization. Might be worth benchmarking that separately, but I didn't want
> to conflate that with this patch.

Okay.

> * I replaced a few more siftup+insert calls with the new combined
> replace-top operation. Because why not.

I suppose that the consistency has value, from a code clarity standpoint.

> Thanks for the patch, Peter, and thanks for the review, Claudio!

Thanks Heikki!

--
Peter Geoghegan