> >> Well, that would certainly be alarming if true, but I don't think it >> is. As far as I can see, the overhead of making the visibility map >> crash-safe is just (1) a very small percentage increase in the work >> being done by VACUUM and (2) a slight possibility of extra work done >> by a foreground process if the visibility map bit changes at almost >> exactly the same time the process was about to insert, update, or >> delete a tuple. >> >> Let's forget the overhead posed by vacuum. Can you please point me to the > design which talks in detail of the second overhead? > > Thanks. >
If you are following the same design that Heikki put forward, then there is a problem with it in maintaining the bits in page and the bits in visibility map in sync, which we have already discussed.