В Пт, 08/07/2022 в 11:04 -0400, Robert Haas пишет: > On Fri, Jul 8, 2022 at 10:11 AM Yura Sokolov <y.soko...@postgrespro.ru> wrote: > > I see analogy with Bus Stop: > > - there is bus stop > > - there is a schedule of bus arriving this top > > - there are passengers, who every day travel with this bus > > > > Bus occasionally comes later... Well, it comes later quite often... > > > > Which way Major (or other responsible person) should act? > > I do not think that is a good analogy, because a bus schedule is an > implicit promise - or at least a strong suggestion - that the bus will > arrive at the scheduled time.
There is implicit promise: those data are written in single row. If you want to notice they are NOT related to each other, return them in different rows or even in different view tables. > In this case, who made such a promise? The original post presents it > as fact that these systems should give compatible answers at all > times, but there's nothing in the code or documentation to suggest > that this is true. > > IMHO, a better analogy would be if you noticed that the 7:03am bus was > normally blue and you took that one because you have a small child who > likes the color blue and it makes them happy to take a blue bus. And > then one day the bus at that time is a red bus and your child is upset > and you call the major (or other responsible person) to complain. > They're probably not going to handle that situation by trying to send > a blue bus at 7:03am as often as possible. They're going to tell you > that they only promised you a bus at 7:03am, not what color it would > be. > > Perhaps that's not an ideal analogy either, because the reported wait > event and the reported activity are more closely related than the time > of a bus is to the color of the bus. But I think it's still true that > nobody ever promised that those values would be compatible with each > other, and that's not really fixable, and that there are lots of other > cases just like this one which can't be fixed either. > > I think that the more we try to pretend like it is possible to make > these values seem like they are synchronized, the more unhappy people > will be in the unavoidable cases where they aren't, and the more > pressure there will be to try to tighten it up even further. That's > likely to result in code that is more complex and slower, which I do > not want, and especially not for the sake of avoiding a harmless > reporting discrepancy. Then just don't return them together, right?
