Re: [WIP Patch] Using 128-bit integers for sum, avg and statistics aggregates

On 2014-10-28 15:54:30 +0200, Heikki Linnakangas wrote:
> On 10/28/2014 03:24 PM, Andres Freund wrote:
> >On 2014-10-28 11:05:11 -0200, Arthur Silva wrote:
> >>On Sat, Oct 25, 2014 at 12:38 PM, Andreas Karlsson <andreas(at)proxel(dot)se>
> >>As far as I'm aware int128 types are supported on every major compiler when
> >>compiling for 64bit platforms. Right?
> >
> >Depends on what you call major. IIRC some not that old msvc versions
> >don't for example. Also, there's a couple 32 platforms with int128 bit
> >support. So I think we should just add a configure test defining the
> >type + a feature macro.
>
> It wouldn't be too hard to just do:
>
> struct {
> int64 high_bits;
> uint64 low_bits;
> } pg_int128;
>
> and some macros for the + - etc. operators. It might be less work than
> trying to deal with the portability issues of a native C datatype for this.

And noticeably slower. At least x86-64 does all of this in hardware...

Greetings,

Andres Freund

--
Andres Freund http://www.2ndQuadrant.com/
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