Re: Extract epoch from Interval weird behavior

Peter Eisentraut <peter.eisentraut@enterprisedb.com> writes:
> We really wanted to avoid doing calculations in numeric as much as 
> possible.  So we should figure out a different way to write this.  The 
> attached patch works for me.  It's a bit ugly since it hardcodes some 
> factors.  Maybe we can rephrase it a bit more elegantly.

I think it's fine but needs some commentary.  Maybe about like
"To do this calculation in integer arithmetic even though
DAYS_PER_YEAR is fractional, multiply everything by 4
and then divide by 4 again at the end.  This relies on
DAYS_PER_YEAR being a multiple of 0.25 and on SECS_PER_DAY
being a multiple of 4."

BTW, it might be good to parenthesize as

(... big calculation ...) * (SECS_PER_DAY/4)

to eliminate any question of whether the value could overflow
before the final division by 4.

            regards, tom lane