On Fri, Nov 6, 2015 at 10:28 AM, Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp> wrote: > > Hello, > > At Fri, 6 Nov 2015 09:49:30 +0530, Amit Kapila <amit.kapila16@gmail.com> wrote in <CAA4eK1L_5T-UYsQeMOrX54g3QeXGhhAk5YFmzZqu5MidzxzkRg@mail.gmail.com> > > Apart from other problems discussed, I think it could also lead to > > a performance penality for the cases when the qual condition is > > costly as evaluating such a qual against lot of dead rows would be a > > time consuming operation. I am not sure, but I think some of the > > other well know databases might not have any such problems as > > they store visibility info inside index due to which they don't need to > > fetch the heap tuple for evaluating such quals. > > I was junst thinking of the same thing. Can we estimate the > degree of the expected penalty using heap statistics? Of couse > not so accurate though. >
I think so. Information related to number of tuples inserted, updated,
hot-updated, deleted and so on is maintained and is shown by
pg_stat_all_tables. By the way, whats your point here, do you mean to
say that we can estimate approximate penality and then decide whether
