Re: ERROR: value out of range: underflow in numeric log calculation

Gallacher Neil <Neil.Gallacher@gstt.nhs.uk> writes:
> When executing log calculations (example below):
> SELECT 1.0 * exp(-1.0 *(ln(2) * (1695993520/86400.0)) / 0.04) AS result_test;
> The following error occurs.
> ERROR: value out of range: underflow

Yup.

> I can however understand that an individual might wish to know that the result of a calculation cannot be represented
bythe system due to its small value however I don't believe it should be the default behaviour. 

You'd be in a minority on that opinion.  In this case you could work
around it by asking for the calculation to be done in numeric rather
than float8:

regression=# SELECT 1.0 * exp(-1.0 *(ln(2::numeric) * (1695993520/86400.0)) / 0.04) AS result_test;




             result_test



                                      

---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

0.00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
(1 row)

but I'm not sure how far that covers your real use-case.

            regards, tom lane