I wrote:
> The weird thing is that after a couple of hours of poking at it with
> oprofile and other sharp objects, I have no idea *why* it's slower.
> oprofile shows just about the same relative percentages for all the
> hot-spot functions in the backend.
However, some comparisons with gprof show that the planner is calling
the hot-spot functions more than it used to, which might be enough to
account for a couple percent on trivial queries like the ones being
issued by pg_bench ("SELECT abalance FROM accounts WHERE aid = :aid;").
After the holiday I'll look into refactoring to try to avoid the
extra calls.
Another issue is that on read-only transactions there's an extra
gettimeofday() call caused by pgstat_report_tabstats, which could be a
problem on machines with slow gettimeofday(). However that shouldn't
happen if you've got track_counts turned off, so if you don't see any
difference with or without stats then it's not the problem for you.
regards, tom lane
