Re: First draft of the PG 15 release notes (sorting)

On Wed, 11 May 2022 at 14:38, Justin Pryzby <pryzby(at)telsasoft(dot)com> wrote:
> I wonder if this is also relevant.
>
> 65014000b35 Replace polyphase merge algorithm with a simple balanced k-way merge.

Thanks for highlighting that. It very much is relevant. In fact, it
seems to account for most of the 25% I mentioned. That particular
test was sorting 10 million tuples with 4MB of work_mem.

I think that "Improve sorting performance (Heikki Linnakangas)" should
be moved out from "E.1.3.1.2. Indexes" and put below "E.1.3.1.4.
General Performance"

The text likely should include the words "disk-based" so that it's
clear that it's not the same as the other line about "in-memory
sorts". I'd also be open to just having a single line too. I'd vote
to put Heikki's name first if we did that.

Maybe:

* Improve performance of sorting tuples (Heikki Linnakangas, Ronan
Dunklau, David Rowley, Thomas Munro)

This improves the merging performance of individual on-disk sort
batches, reduces memory consumption for in-memory sorts and reduces
CPU overheads for certain in-memory sorts.

David