Re: [PATCH] Incremental sort (was: PoC: Partial sort)

Hi,

I've pushed the fist part of this patch series - I've reorganized it a
bit by moving the add_partial_path changes to the end. That way I've
been able to add regression test demonstrating impact of the change on
plans involving incremental sort nodes (which wouldn't be possible when
committing the add_partial_path first). I'll wait a bit before pushing
the two additional parts, so that if something fails we know which bit
caused it.

I've been running extensive benchmarks with the aim to detect any
regressions caused by this patch, particularly during planning. Attached
is the script I've used and spreadsheet with results. The numbers show
throughput with different queries (SELECT, EXPLANN and joins) with the
patches committed one by one. There's quite a bit of noise, even though
the script pins processes to cores and restricts CPU frequency. Overall,
I don't see any obvious regression - the numbers are generally within
0.5% of the master, and the behavior is the same even with -M prepared
which should not be subject to any planner overhead. I do have results
from another machine (2-socket Xeon) but the results are much more
noisy, although the general conclusions are about the same.


regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services