I wrote:
> Looking at this, I wonder if there isn't a bug or at least an
> inefficiency in 8.1. The KeysEqual short circuit tests are still there
> in ri_triggers.c; aren't they now redundant with the test in triggers.c?
> And don't they need to account for the special case mentioned in the
> comment in triggers.c, that the RI check must still be done if we are
> looking at a row updated by the same transaction that created it?
OK, I take back the possible-bug comment: the special case only applies
to the FK-side triggers, which is to say RI_FKey_check, and that routine
doesn't attempt to skip the check on equal old/new keys. I'm still
wondering though if the KeysEqual tests in the other RI triggers aren't
now a waste of cycles.
regards, tom lane