Re: tuplesort memory usage: grow_memtuples

On 16 October 2012 13:42, Peter Geoghegan <peter(at)2ndquadrant(dot)com> wrote:
> On 14 October 2012 09:19, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>> This is a very useful optimisation, for both the low and the high end.
>
> Well, I'm about ready to mark this one "ready for committer". There is
> this outstanding issue in my revision of August 17th, though:
>
> + /*
> + * XXX: This feels quite brittle; is there a better principled approach,
> + * that does not violate modularity?
> + */
> + newmemtupsize = (int) floor(oldmemtupsize * allowedMem / memNowUsed);
> + state->fin_growth = true;
>
> I suppose that I should just recognise that this *is* nothing more
> than a heuristic, and leave it at that.

It's a simple and reasonable heuristic, and a great improvement on the
previous situation.

If you describe in detail that it is a heuristic and why that is
proposed over other approaches that should be sufficient for future
generations to read and understand.

--
Simon Riggs http://www.2ndQuadrant.com/
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