Re: double and numeric conversion

2010/3/3 Yeb Havinga <yebhavinga(at)gmail(dot)com>:
> Pavel Stehule wrote:
>>
>> 2010/3/3 Yeb Havinga <yebhavinga(at)gmail(dot)com>:
>>
>>>
>>> Theo Schlossnagle wrote:
>>>
>>>>
>>>> I didn't look deeply at the postgres internals to see if there was a way
>>>> to do double -> numeric and integer-types -> numeric without
>>>> intermediary
>>>> string format.  If that sort of thing is easy to leverage, I'd be happy
>>>> to
>>>> share the code.
>>>>
>>>>
>>>
>>> I think your code could be valuable for postgres on the fact alone that
>>> it
>>> is almost twice as fast, and probably easy to integrate and unit test. We
>>> make heavy use of the numeric data type, so I'm very interested!
>>>
>>
>> I did some test and numeric->double is about 5% faster than
>> numeric->string->double (on my PC)
>>
>
> numeric_to_double_no_overflow() also uses string as intermediate format.
>
> Theo's conversions are the converse, from double to numeric, and do not use
> string as intermediate format (if I understand it correct). (where
> float8_numeric
> http://doxygen.postgresql.org/backend_2utils_2adt_2numeric_8c.html#2de7f65c8de4b65dad441e77ea1bf402
> does)
>

aha - it is reason why time similar

Pavel

> regards
> Yeb Havinga
>
>