On Wed, Jan 17, 2018 at 2:23 PM, Peter Geoghegan <pg@bowt.ie> wrote:
> A complicating factor for this fix of mine is that mode_final() seems
> to have its own ideas about tuple memory lifetime, over and above what
> tuplesort_getdatum() explicitly promises, as can be seen here:
>
> /*
> * Note: we *cannot* clean up the tuplesort object here, because the value
> * to be returned is allocated inside its sortcontext. We could use
> * datumCopy to copy it out of there, but it doesn't seem worth the
> * trouble, since the cleanup callback will clear the tuplesort later.
> */
> ISTM that either grouping sets or mode_final() must necessarily be
> wrong, because each oversteps, and infers a different contract from
> tuplesort tuple fetching routines (different assumptions about memory
> contexts are made in each case). Only one can be right, unless it's
> okay to have one rule for tuplesort_getdatum() and another for
> tuplesort_gettupleslot() (which seems questionable to me). I still
> think that grouping sets is right (and that mode_final() is wrong). Do
> you?
It would be nice to get an opinion on this mode_final() + tuplesort
memory lifetime business from you, Tom.
Note that you removed the quoted comment within be0ebb65, back in October.
--
Peter Geoghegan