Re: Arbitrary precision arithmatic with pgsql

On 8/31/2004 9:15 AM, Rajesh Kumar Mallah wrote:

> Michael Glaesemann wrote:
> 
>>
>> On Aug 31, 2004, at 9:17 PM, Michael Glaesemann wrote:
>>
>>> What you need is a power operation for numeric, which I think you'd 
>>> have to write yourself,
>>
>>
>> Looking a little closer, there is a pow() function that takes two 
>> numeric arguments and returns numeric.
>>
>> <http://www.postgresql.org/docs/current/static/functions-math.html>
>>
>> test=# select pow(2::numeric,100::numeric);
>>                        pow
>> --------------------------------------------------
>>  1267650600228229401496703205376.0000000000000000
>> (1 row)
>>
>> Sorry for the misinformation.
>>
>> If you'd like, I think you can overload the ^ operator to work on 
>> numeric as well if you don't want to use pow(). See the following page 
>> for more information.
>>
>> <http://www.postgresql.org/docs/current/static/sql-createoperator.html>
> 
> 
> Yep thats cool.  Thanks for the research!
> 
> but i still wonder if a warning or info message were
> appropriate at some stage so that people do not confuse it
> with sielent loss of accuracy . I know this example is *not* a
> case of where postgresql is truncating data at the insert level
> (like mysql does) but at the calculation level.

I agree that doing
    select 2::numeric ^ 100;

should emit some sort of a warning. Because what happens here is that 
the numeric value is degraded to a float8 in order to use the operator.

I don't think that
    select 2 ^ 100;

should emit the same warning.


Jan

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