David Rowley <david.row...@2ndquadrant.com> writes: > On Wed, 17 Jul 2019 at 11:06, Tom Lane <t...@sss.pgh.pa.us> wrote: >> (Actually, I doubt that any of these changes will really move the >> performance needle in the real world. It's more a case of wanting >> the code to present good examples not bad ones.)
> In spirit with the above, I'd quite like to fix a small bad example > that I ended up with in nodeAppend.c and nodeMergeappend.c for > run-time partition pruning. I didn't test the patch, but just by eyeball it looks sane, and I concur it should win if the bitmap is sparse. One small question is whether it loses if most of the subplans are present in the bitmap. I imagine that would be close enough to break-even, but it might be worth trying to test to be sure. (I'd think about breaking out just the loops in question and testing them stand-alone, or else putting in an outer loop to repeat them, since as you say the surrounding work probably dominates.) regards, tom lane