Robert Haas <robertmhaas@gmail.com> writes:
> Oh, but it's worse than that. When you XLOG a WAL record for each of
> those pages, you're going to trigger full-page writes for all of them.
> So now you've turned 1GB of data to write into 2+ GB of data to
> write.
No, because only the first mod of each VM page would trigger a full page
write, at least assuming a reasonable ordering of the operations.
regards, tom lane