Re: Text to interval conversion can silently truncate data

Jack Christensen <jack(at)jackchristensen(dot)com> writes:
> jack=# select '1.51 years'::interval = '1.52 years'::interval;
> ?column?
> ----------
> t
> (1 row)

> This is surprising. Once I looked at the C code for Interval it makes
> more sense given that it cannot represent fractional years, months, or
> days. Wouldn't it make more sense to raise an invalid input error than
> to silently truncate data?

Well, "1.5 years" is perfectly valid (it means 18 months). So I don't
think rejecting fractional years altogether would be a good idea.

Really your complaint is not very different from complaining because
1.23456789::float4 = 1.234567891::float4. It's just a property of the
datatype that certain inputs aren't represented exactly. Another example
that stays within the interval datatype is

regression=# select '1.000001 seconds'::interval;
interval
-----------------
00:00:01.000001
(1 row)

regression=# select '1.0000001 seconds'::interval;
interval
----------
00:00:01
(1 row)

I doubt people would thank us for rejecting that second input altogether.

regards, tom lane