On 08/03/2018 06:40 AM, Kyotaro HORIGUCHI wrote:
> ...
>
> I'm not confident on replacing double to float8 partially in gist
> code. After the 0002 patch applied, I see most of problematic
> usage of double or bare arithmetic on dimentional values in
> gistproc.c.
>
>> static inline float
>> non_negative(float val)
>> {
>> if (val >= 0.0f)
>> return val;
>> else
>> return 0.0f;
>> }
>
> It is used as "non_negative(overlap)", where overlap is float4,
> which is calculated using float8_mi. Float4 makes sense only if
> we need to store a large number of it to somewhere but they are
> just working varialbles. Couldn't we eliminate float4 that
> doesn't have a requirement to do so?
>
I'm not sure I follow. The patch does not modify non_negative() at all,
and we still call it like this:
if (non_negative(overlap) < non_negative(context->overlap) ||
(range > context->range &&
non_negative(overlap) <= non_negative(context->overlap)))
selectthis = true;
where all the "overlap" values are still float4. The only thing that
changed here is that instead of doing the arithmetic operations directly
we call float8_mi/float8_div to benefit from the float8 handling.
So I'm not sure how does the patch beaks this? And what do you mean by
'eliminate float4'?
thank you
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
