Thanks for taking a look at it. > I first tried just the compare_fuzzy_path_costs() change and really > couldn't measure any reliable difference. oprofile output for CVS HEAD > looks like
Well, there's obviously something different between your case and mine, because in my query add_path was the #1 CPU hog and it wasn't close. I suspect my query had more joins - I'll take a look at yours. > It gets worse though: add_similar_paths is flat *wrong*. It compares > each successive path to only the current cheapest-total candidate, > and thus is quite likely to seize on the wrong cheapest-startup path. > I tried fixing its loop logic like so: Nuts. That's probably a fatal defect. > Now, maybe if we could force the compiler to inline > compare_fuzzy_path_costs we could buy some of that back. Another > possibility is to contort add_similar_path some more so that it avoids > double comparisons so long as cheapest_total and cheapest_startup are > the same path; I have a feeling that's not going to win much though. Agreed. > So it's kind of looking like a dead end from here. But in any case the > patch isn't acceptable as-is with that fundamental logic error in > add_similar_paths, so I'm bouncing it back for rework. ...Robert -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
