Re: [Patch] Log10 and hyperbolic functions for SQL:2016 compliance

From: Lætitia Avrot <laetitia(dot)avrot(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Pg Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [Patch] Log10 and hyperbolic functions for SQL:2016 compliance
Date: 2019-01-27 19:39:41
Message-ID: CAB_COdiQNzGhDvE8cn4ctBZhMXwy8tm8uxo0FATpP4TeM5Jg+A@mail.gmail.com
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Hi,

Thanks for your time and advice, Tom!

> > [ adding_log10_and_hyperbolic_functions_v1.patch ]
>
> No objection to the feature, but
>
> - Why are you using the float4-width library functions (coshf etc)
> rather than the float8-width ones (cosh etc)?
>
> Well, I guess the only reason is that I wasn't paying attention enough...
I changed for the float8-width library functions.

> - I wonder whether these library functions exist everywhere.
> If they don't, what will we do about it ... throw an error?
>
> I see that SUSv2 requires cosh() and so on, so it's quite possible
> that these do exist everywhere we care about. I'd be okay with
> throwing a patch onto the buildfarm to see, and adding an autoconf
> test only if the buildfarm is unhappy. But we should be clear on
> what we're going to do about it if that happens.
>
> I think I was too confident because of the "it works on my laptop"
syndrome... I don't know how to answer to this point.

> > I added regression tests for the new functions, but I didn't for log10
> > function, assuming that if log function worked, log10 will work too.
>
> Not quite sure I believe that.
>
> Do you mean I should also add a regression test for the new log10 function
too ?

> Actually, what I'd counsel is that you *not* include tests of what
> these do with Inf and NaN. There is no upside to doing so, and lots
> of downside if older platforms are squirrely in their behavior, which
> is hardly unlikely (cf opossum ...)
>

I changed the regression tests for hyperbolic functions, so it doesn't test
for Inf and NaN.

You'll find enclosed the new version of the patch.

Cheers,

Lætitia

Attachment Content-Type Size
adding_log10_and_hyperbolic_functions_v2.patch text/x-patch 6.9 KB

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