On Wednesday, May 21, 2014, Jeff Janes <jeff.ja...@gmail.com> wrote: > > On Wed, May 21, 2014 at 1:11 PM, Joe Van Dyk > <j...@tanga.com<javascript:_e(%7B%7D,'cvml','j...@tanga.com');> > > wrote: > >> I came across http://bonesmoses.org/2014/05/14/foreign-keys-are-not-free/ >> which seems to indicate so. >> >> When I run the following test script, having 50 foreign keys takes >> about twice as long to do the update. Is there a reason for that? >> Seems like the RI triggers wouldn't have to run on updates if the >> value doesn't change. >> > > That's kind of a question of definitions. Perhaps the trigger itself > doesn't need to run, but the code that decides whether the trigger needs to > run does need to run. Where do you draw the line around what is the > trigger proper and what is just infrastructure? > > However you wish to define it, change your function so that it actually > does change the key field, and see how much slower that is than the > behavior where you update the row without updating the key. > >
I was expecting that the RI update triggers would have a "when (new.key is distinct from old.key)" condition on them, which would mean that the number of referencing tables wouldn't matter. > Cheers, > > Jeff >
