Laurenz Albe <laurenz.albe@cybertec.at> writes:
> On Sat, 2022-12-03 at 08:54 +0000, PG Doc comments form wrote:
>> I am thinking that the value of the ROUND function with NUMERIC as an
>> argument is rounded off, not rounded away from zero.
> It is rounded away from zero, since 43 is farther away from 0 than 42.5.
> This may be a language problem.
Perhaps, since I don't see anything wrong with that text either.
(Of course, it's moderately likely that I wrote that text,
or at least copy-edited it at some point ;-). Don't remember.)
The point is that for 42.5, or anything-point-5, the basic
"round to nearest integer" rule is insufficient because 42 and
43 are equally near. We need a tie-breaking rule, and for numeric
that rule has historically been to round to the larger absolute
value (or "away from zero", as the text puts it to avoid two-dollar
terminology). Sadly, that is not what IEEE has established as
best practice for floating-point rounding, so round(float8)
acts differently.
regards, tom lane