>
>
> If you have a scenario where the visibility map incurs a measurable
> overhead, let's hear it. I didn't see any in the tests I performed, but
> it's certainly possible that if the circumstances are just right it
> makes a difference.
>
> Heikki,
The obvious one, i could observe is that it would increase the WAL
contention. Am i missing something? All i am suggesting is to reduce the
unnecessary work required in those tables, where the visibility map is not
required. For example, in data warehouses, people might even have a tables
without any indexes. Why do we ask them to incur the overhead of visibility
map?
Also since you have made the visibility maps without any page
level locking, have you considered whether it would make sure the correct
order of inserts into the WAL? i have looked at some random threads, but i
couldn't get the complete design of visibility map to be used for index only
scans.
Thanks,
Gokul.
