Hello,
Sorry for the confusion, I wasn't aware that SQL pow changed types
depending on the input value.
Indeed, this is quite strange...
fabien=# SELECT i, POW(2, i) FROM generate_series(-2, 2) AS i;
-2 | 0.25
-1 | 0.5
0 | 1
1 | 2
2 | 4
I've modified the function to match more closely the behaviour of SQL,
except that 0^(negative) returns 'double inf'. Do you think there is any
value in raising an error instead?
fabien=# SELECT POW(0,-1);
ERROR: zero raised to a negative power is undefined
Hmmmm... I'm fine with double inf, because exception in pgbench means the
end of the script, which is not desirable for benchmarking purposes.
I think that:
- you can simplify the ipow function by removing handling of y<0 case,
maybe add an assert to be sure to avoid it.
- you should add more symmetry and simplify the evaluation:
if (int & int)
{
i1, i2 = ...;
if (i2 >= 0)
setIntValue(retval, ipow(i1, i2));
else
// conversion is done by C, no need to coerce again
setDoubleValue(retval, pow(i1, i2));
}
else
{
d1, d2 = ...;
setDoubleValue(retval, pow(d1, d2));
}
Add a test case to show what happens on NULL arguments, hopefully the
result is NULL.
--
Fabien.
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