On Tue, May 26, 2020 at 5:40 PM Jeff Davis <pgsql@j-davis.com> wrote:
On Tue, 2020-05-26 at 21:15 +0200, Tomas Vondra wrote: > > As for the tlist fix, I think that's mostly ready too - the one thing > we > should do is probably only doing it for AGG_HASHED. For AGG_SORTED > it's > not really necessary.
Melanie previously posted a patch to avoid spilling unneeded columns, but it introduced more code:
and it seems that Heikki also looked at it. Perhaps we should get an acknowledgement from one of them that your one-line change is the right approach?
I spent some time looking at it today, and, it turns out I was wrong.
I thought that there was a case I had found where CP_SMALL_TLIST did not eliminate as many columns as could be eliminated for the purposes of spilling, but, that turned out not to be the case.
I changed CP_LABEL_TLIST to CP_SMALL_TLIST in create_groupingsets_plan(), create_agg_plan(), etc and tried a bunch of different queries and this 2-3 line change worked for all the cases I tried. Is that where you made the change? And then are you proposing to set it based on the aggstrategy to either CP_LABEL_TLIST or CP_SMALL_TLIST here?