Re: tuplesort_gettuple_common() and *should_free argument

On Wed, Jan 25, 2017 at 3:11 PM, Peter Geoghegan <pg(at)heroku(dot)com> wrote:
> On Wed, Jan 25, 2017 at 3:11 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Please. You might want to hit the existing ones with a separate patch,
>> but it doesn't much matter; I'd be just as happy with a patch that did
>> both things.
>
> Got it.

Attached is a patch that does both things at once. The internal
function tuplesort_gettuple_common() still mentions repeated fetches,
since that context matters to its internal callers. The various
external-facing functions have a simpler, stricter contract, as
discussed.

I didn't end up adding a line like "copy=FALSE is recommended only
when the next tuplesort manipulation will be another
tuplesort_gettupleslot fetch into the same slot", which you suggested.
When the tuplesort state machine is in any state following
"performing" a sort, there are very few remaining sane manipulations.
Just things like skipping or seeking around for tuples, and actually
ending the tuplesort and releasing resources.

--
Peter Geoghegan