Bruce Momjian <pgman@candle.pha.pa.us> writes:
> Is it because we take a snapshot of the page before we write it in case
> we only write part of the page?
AFAIR, the partial-page-write problem is the entire reason for doing it.
If we could be certain that writes to datafile pages were atomic, we'd
not need this.
Of course we can't be certain of that. But I'm wondering if there isn't
a cheaper solution.
regards, tom lane