Re: rounding_up

Tom Lane <tgl@sss.pgh.pa.us>

From: Tom Lane <tgl@sss.pgh.pa.us>
To: Christoph Moench-Tegeder <cmt@burggraben.net>
Cc: Daria Shanina <vilensipkdm@gmail.com>, pgsql-hackers@lists.postgresql.org
Date: 2025-04-14T14:26:42Z
Lists: pgsql-hackers
Christoph Moench-Tegeder <cmt@burggraben.net> writes:
> ## Daria Shanina (vilensipkdm@gmail.com):
>> I noticed, when we parse and validate values (in particular, the int type),
>> we use the *rint* method, but unfortunately it does not work according to
>> the round rules.

> First question would be "which round rule?" as (of course) there're
> multiple to chose from.

Yeah.  Round-to-nearest-even is a well-respected rule, which is why
it's the default per IEEE 754.  I don't see a good reason for us
to switch.  Even if someone advanced an argument, it would have
to be a *mighty* convincing argument to justify breaking backwards
compatibility here.

I do find it a little unfortunate that our numeric type does it
differently than our float types.  Again though, there's a huge
compatibility argument against changing that now.  It does give
you an "out" if you really need one or the other behavior for
a particular application: you can cast to numeric or float8
before casting to int.

			regards, tom lane