That's because numerics default to 16 or something similar. If you want
more precision just explicitly cast it:
decibel=# select power(0.1::numeric(20,20),17);
0.00000000000000001000
On Fri, May 20, 2005 at 09:30:16AM -0700, Stephan Szabo wrote:
>
> On Fri, 20 May 2005, Tom Lane wrote:
>
> > Has anyone bothered to actually look into the code?
> >
> > regression=# select power(2::numeric,1000);
> >
> > power
> > ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> >
> > 10715086071862673209484250490600018105614048117055336074437503883703510511249361224931983788156958581275946729175531468251871452856923140435984577574698574803934567774824230985421074605062371141877954182153046474983581941267398767559165543946077062914571196477686542167660429831652624386837205668069376.0000000000000000
> > (1 row)
> >
> > AFAICT the only thing missing is a pg_operator entry linked to the
> > function.
>
> It appears fairly limited however given that you rapidly run into the
> numeric maximum length for exp.
>
> It also doesn't seem to work terribly well:
>
> sszabo=# select power(0.1::numeric, 15);
> power
> --------------------
> 0.0000000000000010
> (1 row)
>
> sszabo=# select power(0.1::numeric, 16);
> power
> --------------------
> 0.0000000000000001
> (1 row)
>
> sszabo=# select power(0.1::numeric, 17);
> power
> --------------------
> 0.0000000000000000
> (1 row)
>
> sszabo=# select power(0.1::numeric, 17)*100;
> ?column?
> --------------------
> 0.0000000000000000
> (1 row)
>
>
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--
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