Re: longs where uint64s could be

On Fri, Jan 17, 2020 at 05:12:20PM -0800, Peter Geoghegan wrote:
> On Fri, Jan 17, 2020 at 4:42 PM David Fetter <david(at)fetter(dot)org> wrote:
> > While going over places where I might use compiler intrinsics for
> > things like ceil(log2(n))) and next power of 2(n), I noticed that a
> > lot of things that can't be fractional are longs instead of, say,
> > uint64s. Is this the case for historical reasons, or is there some
> > more specific utility to expressing as longs things that can only have
> > non-negative integer values? Did this practice pre-date our
> > now-required 64-bit integers?
>
> Yeah, it's historic. I wince when I see "long" integers. They're
> almost wrong by definition. Windows has longs that are only 32-bits
> wide/the same width as a regular "int". Anybody that uses a long must
> have done so because they expect it to be wider than an int, even
> though in general it cannot be assumed to be in Postgres C code.
>
> work_mem calculations often use long by convention. We restrict the
> size of work_mem on Windows in order to make this safe everywhere. I
> believe that this is based on a tacit assumption that long is wider
> outside of Windows.
>
> logtape.c uses long ints. This means that Windows cannot support very
> large external sorts. I don't recall hearing any complaints about
> that, but it still doesn't seem great.

Please find attached a patch that changes logtape.c and things in near
dependency to it that changes longs to appropriate ints.

Best,
David.
--
David Fetter <david(at)fetter(dot)org> http://fetter.org/
Phone: +1 415 235 3778

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